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Page 113
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 113
Page 114
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 114
Page 115
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 115
Page 116
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 116
Page 117
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 117
Page 118
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 118
Page 119
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 119
Page 120
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 120
Page 121
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 121
Page 122
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 122
Page 123
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 123
Page 124
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 124
Page 125
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 125
Page 126
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 126
Page 127
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 127
Page 128
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 128
Page 129
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 129
Page 130
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 130
Page 131
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 131
Page 132
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 132
Page 133
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 133
Page 134
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 134
Page 135
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 135
Page 136
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 136
Page 137
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 137
Page 138
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 138
Page 139
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 139
Page 140
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 140
Page 141
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 141
Page 142
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 142
Page 143
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 143
Page 144
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 144
Page 145
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 145
Page 146
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 146
Page 147
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 147
Page 148
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 148
Page 149
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 149
Page 150
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 150
Page 151
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 151
Page 152
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 152
Page 153
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 153
Page 154
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 154
Page 155
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 155
Page 156
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 156
Page 157
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 157
Page 158
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 158
Page 159
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 159
Page 160
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 160
Page 161
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 161
Page 162
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 163
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Page 171
Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
Page 179
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
×
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Suggested Citation:"Part II - Research Report." National Academies of Sciences, Engineering, and Medicine. 2014. Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report. Washington, DC: The National Academies Press. doi: 10.17226/22473.
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Research Report P A R T I I

117 S U M M A R Y This report presents the findings of a research project that explored the potential impacts of climate change and extreme weather on the U.S. highway system. A conceptual framework of the highway network consisting of a road segment, corridor, and network was developed to illustrate how climate change could affect the road system. There are five key components to the design of a typical road segment—subsurface/foundation conditions, materials speci- fications, structures, typical cross sections, and drainage/erosion—that could be affected by some change in environmental conditions such as precipitation, temperature, and wind. Design standards, guidelines, and standard operating procedures have been in place in many transportation agencies for many years and most of these procedures, etc. were based on historical records of environmental conditions. As conditions change, it is likely that some of these procedures will have to change as well to reflect new circumstances and environmental stressors. At the corridor level, the potential impacts of changing environmental conditions due to climate change on a typical road segment would accumulate over a corridor and throughout the network where similar circumstances exist. In addition, corridor-level concerns with changing environmental conditions will likely relate to outside-of-right-of-way environ- mental mitigation; erosion, drainage, and runoff impacts; right-of-way maintenance; and construction practices and activities. For example, changes in temperature and precipitation and the corresponding need to utilize different construction materials could affect construc- tion practice. A lengthening or shortening of the construction season could also influence a transportation agency’s construction program. The network-level focus relates to the overall management of the highway network, including building and protecting the agency’s assets from climate stressors as well as devel- oping system management strategies for expected disruptions. Specific climate change- related concerns at the network level relate to alternate routes and corresponding system operations strategies; the connection to intermodal facilities; location engineering (where to put the facility to begin with); and protecting building and other agency assets. In examining the future U.S. socio-demographic context for climate change, the report concludes that: • The U.S. population will continue to grow with most of this growth occurring in urban areas and in parts of the country expecting notable changes in climate. • The composition of this population will be very different than it is today, with more diverse populations and elderly in the nation’s population mix. • Significant levels of housing and corresponding development will be necessary to provide places to live and work for this population, with much of this development likely to occur in areas subject to changing environmental conditions. Climate Change, Extreme Weather Events, and the Highway System: Research Report

118 • Increasing population growth will create new demands for transportation infrastructure and services, once again in areas that are vulnerable to changing climate conditions. • The nation’s highway system will be facing increasing demands for reconstruction and reha- bilitation over the next 40 years (to 2050), which provides an opportunity to incorporate climate adaptation strategies into such efforts, if appropriate. The research used climate change models to project future climate conditions. The mod- els showed that temperatures in the lower 48 states are projected to increase about 2.3°C (4.1°F) by 2050 relative to 2010. While all U.S. regions are projected to increase in tempera- ture, the amounts will vary by location and season. In general, areas farther inland will warm more than coastal areas, because the relatively cooler oceans will moderate the warming over coastal regions. In addition, northern areas will warm more than southern areas because there will be less high-latitude snow cover to reflect sunlight. More warming is projected for northern and interior regions in the lower 48 states than for coastal and southern regions. In general, the models project, and observations also show, that the Northeast and Mid- west are likely to become wetter while the Southwest is likely to become drier. In addition, all the climate models project an increase in precipitation in Alaska. It is not known whether precipitation will increase in other areas such as the Northwest or the Southeast. While the models tend to show a drier Southwest and a wetter Northeast and Midwest, the differences across the models mean it is not possible to forecast exactly which localities become wet- ter or drier nor where the transitions between wet and dry areas lie. Climate models tend to project relatively wetter winters and drier summers across most of the United States. However, this does not mean that all areas are projected to receive more precipitation in the winter and less precipitation in the summer. The models also project a larger increase in summer temperature than winter temperature. Extreme temperatures will get higher. This means that all locations will see increases in the frequency and duration of occurrence of what are now considered extreme temperatures such as days above 32°C (90°F) or 35°C (95°F). In the long run, the number of days below freezing will decrease in many areas, particularly southern locations. Precipitation intensities (both daily and 5-day) are projected to increase almost every- where, although the largest increases tend to happen in more northern latitudes. Recent research has suggested that there could be fewer hurricanes, but the ones that do occur, particularly the most powerful ones, will be even stronger. Global sea levels are rising. Projections of future sea-level rise vary widely. The Inter- governmental Panel on Climate Change (IPCC) projects that the sea level will rise 8 inches to 2 feet (0.2 to 0.6 meter) by 2100 relative to 1990. Several studies published since the IPCC Fourth Assessment Report, however, estimate that sea levels could rise 5 to 6.5 feet (1.5 to 2 meters) by 2100. Sea-level rise seen at specific coastal locations can vary considerably from place to place and from the global mean rise because of differences in ocean temperatures, salinity, and currents and because of the subsidence or uplift of the coast itself. A diagnostic framework was developed that provides highway agency staff with a general step-by-step approach for assessing climate change impacts and deciding on a course of action. The framework, which can be applied at the systems planning level down to the scale of individual projects, consists of: Step 1: Identify key goals and performance measures for the adaptation planning effort. Step 2: Define policies on assets, asset types, or locations that will receive adaptation consideration. Step 3: Identify climate changes and effects on local environmental conditions. Step 4: Identify the vulnerabilities of asset(s) to changing environmental conditions.

119 Step 5: Conduct risk appraisal of asset(s) given vulnerabilities. Step 6: Identify adaptation options for high-risk assets and assess feasibility, cost effective- ness, and defensibility of options. Step 7: Coordinate agency functions for adaptation program implementation (and option- ally identify agency/public risk tolerance and set trigger thresholds). Step 8: Conduct site analysis or modify design standards (using engineering judgment), operating strategies, maintenance strategies, construction practices, etc. This eight-step process is inherently a multidisciplinary and collaborative one. It is not likely that a state transportation agency has internal staff capability on climate science. In most cases, these agencies have been working with the local university or the state clima- tologist in order to obtain such input. In many cases, the vulnerability and risk assessment process depends on local input on what is considered to be the most critical assets in an urban area. Importantly, the actions taken by local communities and governments, such as land use approval and street/drainage design, could have significant impact on the ability of state assets to handle larger loads, and thus the need for coordination. A range of impacts on the highway system can be anticipated from different climate stress- ors. These impacts include both impacts to the infrastructure itself (and thus how facilities are designed and constructed) and to operations and maintenance. In addition to the direct effects of climate changes on highways, climate change will affect ecological dynamics in ways that will have implications for transportation systems. The strategies for dealing with climate change and extreme weather events will differ by functional activity within a trans- portation agency. For example, climate change adaptation can be considered in planning, environmental analysis, design, infrastructure retrofit, construction, operations, mainte- nance, emergency response, and public outreach and communications. Each activity will usually require different analysis approaches, data, and resulting strategies. Of particular interest, as agencies increasingly adopt transportation asset management (TAM) approaches, opportunities will exist to integrate consideration of weather risk and climate change into TAM objectives, data collection, performance measurement, monitor- ing, and resource allocation decisions. Over time, the integration of weather and climate information into TAM will help agencies make targeted investments or allocation decisions that will increase the resilience of the network and of individual assets to changing environ- mental conditions. Most agencies that are concerned about adaptation begin by conducting a risk assessment of existing assets. Most of these risk assessments remain largely qualitative and based on professional judgment. Climate-related risk is more broadly defined in that risk can relate to impacts beyond simply the failure of the asset. It relates to the failure of that asset in addition to the consequences or magnitudes of costs associated with that failure. In this case, a con- sequence might be the direct replacement costs of the asset, direct and indirect costs to asset users, and, even more broadly, the economic costs to society given the disruption to trans- portation caused by failure of the asset or even temporary loss of its services (e.g., a road is unusable when it is under water). An integrated risk assessment is performed on vulnerable assets with the assessment considering the likelihood of impacts and their consequences. These two factors are related to each other and their intersection determines the risk level facing an asset. Adaptation options can then be considered for high- or medium-risk assets while low-risk assets are given lower priority. Most studies have adopted a qualitative assessment of the risks associated with specific transportation assets. Although the definition of risk includes some indication of probable occurrence, in reality, such probabilities are hard to formulate, especially when considering that the occurrence in question might not be real until many years into the future. To account

120 for this uncertainty, most studies have relied on qualitative or subjective assignment of risk. Thus, “high,” “medium,” or “low” is often used to indicate the level of risk associated with individual assets. Even those approaches considered more quantifiable use ordinal rankings of values, that is, “1,” “2,” or “3” to indicate relative risk. The intent of these approaches is straightforward—to provide decision makers with some sense of where investment in the transportation system would provide the greatest reduction in risk associated with climate change-related disruptions. Few agencies have gone to the point of systematically inventorying their assets to identify how each transportation link or facility will be affected by climate change. Nonetheless, as some states have finished their initial efforts at adaptation planning, some have begun the process of identifying vulnerabilities to their transportation infrastructure in a more com- prehensive manner. There is a growing understanding among researchers and highway officials that climate change and extreme weather events are a threat to many aspects of the highway system, which warrants spending resources to investigate the specific risks they pose. Both domesti- cally and internationally, however, limited action has been taken “on the ground” to build resiliency into the transportation system. Indeed, with some notable exceptions, much adap- tation work remains at a planning or risk assessment level and has yet to be incorporated into the design of individual projects. This is likely to change in the near future as the risk assessment studies progress and as transportation officials begin to realize that in certain areas a changing climate could have significant impact on highway planning, design, con- struction, and operations/maintenance. Although some question the projections of future climate conditions, most agree that the United States has experienced record extreme weather events over the past several years. The frequency and severity of such events have seemed to increase; infrastructure dam- age and community costs have risen; the impact of recovery costs on maintenance budgets and on regular operations activities continues to become more significant; and perhaps, most importantly, public expectations of a transportation agency’s ability to recover the transportation system quickly and efficiently have increased greatly. In several instances, the recurring pressures on state transportation officials to prepare for, manage, and recover from extreme weather events have caused organizational change, development of new man- agement responsibilities (e.g., emergency management officials), modification of standard operating procedures, and staff training in managing and administering recover efforts. This report recommends steps that can be taken by transportation agencies to prepare for extreme weather events, manage agency operations during the event, and conduct post- recovery operations. The final section of the report offers 27 suggestions for further research and information dissemination. These recommendations are categorized into five major topics: planning; project development; construction, operations, and maintenance; system management and monitoring; and an “other” category that focuses on institutional capacity building.

121 1.1 Introduction Climate change has received increasing attention world- wide as potentially one of the greatest challenges facing modern society. This attention has focused particularly on two topics. First (and the one receiving the most attention), how can greenhouse gas (GHG) emissions be reduced to decrease the rate and threat of climate change? Second, how can a future world be prepared for changing climatic condi- tions that are likely even if the pace and magnitude of the level of emissions entering the atmosphere are successfully reduced? Over time, sea-level rise threatens to permanently inundate low-lying communities and their transportation facil ities such as coastal highways and ports (Suarez et al. 2005). Increased risk of coastal flooding in conjunction with sea-level rise, however, may pose a more serious risk than inundation alone. Climate change science suggests that the intensity of storms, particularly the most powerful hurricanes, will increase in the future. This means stronger winds and higher storm surges— on top of higher sea levels, which will put even more land and transportation facilities at risk. Very high temperatures can cause concrete pavements to buckle and can soften asphalt roads, leading to rutting and subsidence. High temperatures will cause more precipitation to fall as rain rather than snow, which may reduce transportation disruptions, but increase drainage problems. The melting of the permafrost will create significant challenges to road design and maintenance (as is happening in Alaska). Increased frequency of freeze–thaw cycles could significantly affect pavement designs. Precipita- tion patterns and intensity could change dramatically, affect- ing transportation networks and facility operations. Some areas may face increased precipitation and increased flood- ing. For example, climate models tend to project increased winter precipitation in the Midwest and Northeast, increas- ing the risk of early spring flooding as snow packs melt. Pre- cipitation intensity is projected to increase even more in the future, increasing the risk of flooding, particularly from con- vective thunderstorms in the summer. Extreme weather events are symptomatic of the type of weather many climate scientists believe will be seen more in the future, and which will significantly impact state depart- ments of transportation (DOT) operations. The year 2012 set a record for extreme weather events, with 3,527 monthly weather records broken for heat, rain, and snow in the United States, according to information from the National Climatic Data Center (NOAA 2013). The National Resources Defense Council’s (NRDC) website on extreme weather noted the hottest March on record in the contiguous United States, and July was the hottest single month ever recorded in the lower 48 states (NRDC 2013). The United States experienced the worst drought in 50 years across the nation’s Midwest and South, with over 1,300 U.S. counties across 29 states declared drought disaster areas. Wildfires burned over 9.2 million acres, with the average size of the fires setting an all-time record of 165 acres per fire. Hurricane Sandy’s storm surge height (13.88 feet) broke the all-time record in New York Harbor and brought record devastation across New Jersey and New York with floodwaters and winds. A sampling of states from the NRDC website gives a sense of the magnitude of extreme weather events: California: A total of 37 broken heat records, 5 broken snow records, 53 broken precipitation records, and 102 large wildfires Kansas: A total of 64 broken heat records, 42 broken precipitation records, and 30 large wildfires Montana: A total of 59 broken heat records, 16 broken snow records, 17 broken precipitation records, and 128 large wildfires Texas: A total of 144 broken heat records, 8 broken snow records, 115 broken precipitation records, and 34 large wildfires C H A P T E R 1 Introduction and Research Objectives

122 In addition to the direct effects on road infrastructure, changing climate conditions can affect many of the ecological functions of lands surrounding roads, and possibly influ- ence existing wetland and habitat banks and environmental mitigation strategies that are commonly considered today by state transportation agencies as part of the project devel- opment process. Thus, future highway projects might face very different environmental mitigation requirements than they do today. An ever-increasing number of state and local officials have begun to examine how activities in their jurisdiction could be affected by changes in such environmental conditions. In almost all of these efforts, the transportation system has been identified as one of the most important sectors that could face significant impacts of a changing climate and of extreme weather events. The basic premise of road design is that the physical form and materials specifications associated with the design itself must reflect the environmental conditions within which the facility is constructed. Operational and mainte- nance strategies must relate to the “external” conditions that affect system performance. The highway project development process must take into consideration likely impacts on envi- ronmental resources resulting from the combined effect of changing climatic conditions and the associated changes in the physical and operational characteristics of infrastructure that will be required. A strategic perspective and specific guidance are needed on how the transportation sector can best prepare for likely changes in environmental conditions over the next half cen- tury. Many, for example, are interested in incorporating climate change considerations in a strategic asset management system that provides a systematic approach to changing some ele- ments of infrastructure characteristics at the appropriate time. By starting early, and by integrating the strategies and actions needed to address anticipated effects of climate change as part of an ongoing process of infrastructure preservation and asset management, and by doing this over a period of decades, the transportation community can be prepared for these impacts. And it will have to be done in a way that is affordable, avoiding the far more costly approaches of responding to short-term “crash programs” or, even worse, the need to rebuild facilities that suffer sudden and potentially catastrophic damage as a result of extreme weather events. At the same time, the transportation sector cannot afford to over-invest in climate adaptation. With limited budgets and a large backlog of infrastructure needs, transportation agencies will need to use the most cost-effective strategies, from retrofitting existing infrastructure to strengthening design standards for new infrastructure. A flexible framework for guiding the timing and sequence of climate adaptation investments is needed. 1.2 Problem Statement and Research Objectives The goal of this research was to provide insights, guidance, and tools to mitigate the risks of climate change impacts on the nation’s highway systems and related intermodal facili- ties. The objectives were to (1) synthesize the current state of knowledge on the range of impacts of climate change on the highway system by region of the United States for the period 2030–2050; (2) recommend institutional arrange- ments, tools, approaches, and strategies that state DOTs can use during the different stages of planning and project devel- opment and system management to adapt both infrastruc- ture and operations to these impacts; (3) prepare guidance, materials, and methods for dealing with these impacts; and (4) identify future research and activities needed to improve understanding of possible impacts and the steps needed for adaptive system management. Note that Part I of this volume, the Practitioner’s Guide, accomplishes the third objective. 1.3 Study Scope and Research Approach This study examined potential climate change impacts on the U.S. highway system. Although there are references to impacts and studies on other parts of the nation’s transportation sys- tem, the study focuses on highways. In many ways, however, the results of this research can be used by those responsible for non-highway modal operations. For example, impacts and adaptation strategies for pavements would be of interest to those responsible for airport and transit paved surfaces. Drain- age and temperature stresses are common to all transportation modes, and thus the information provided in this report would be of interest to those concerned with such issues. The diagnos- tic framework for adaptation planning presented in this report is also defined in such a way as to provide guidance to those interested in any mode of transportation. An important boundary of this analysis was the projection of climate impacts and identification of potential adapta- tion strategies to the target year of 2050. It is understandable that 2050 was chosen by the oversight panel as the target year given a desire to produce research results that can be used by transportation officials today. However, climate modeling suggests that the major climate change-related impacts to the transportation system are not likely to occur until the latter part of the century. The major exception to this are extreme weather events, which in recent years have focused attention on the record precipitation, heat, and dangerous storms being experienced in all parts of the country. The target year of 2050 was maintained in the research, except in one case, sea-level rise. The research team felt that the rise in sea level over the next 40 years was not likely to cause that

123 significant a challenge in most coastal parts of the country. Thus, projections of sea-level rise were provided for both years 2050 and 2100. It is interesting to note that much of the literature and con- cern relating to climate change seems to be centered on coastal impacts, primarily from sea-level rise combined with storm surge. Clearly, such impacts are significant and deserving of attention. However, this study describes other impacts relating to drought, wildfires, dust, wind, and heavy storms that will likely affect non-coastal states. Climate change and extreme weather events are not just a concern for coastal communities. This report adopts this wider perspective on both the impacts and potential adaptation strategies. The report provides numerous references on adaptation efforts throughout the world, with emphasis given to the United States. However, except in several instances (and once again primarily focused on water and precipitation impacts), much of the progress in adaptation planning has occurred overseas in countries such as Australia, Sweden, and the United Kingdom. The scope of the literature review and references to specific adaptation-related topics thus includes numerous examples from other countries. The literature on transportation adaptation planning is rapidly expanding, especially in response to federally funded pilot projects that aim to highlight the characteristics and key factors associated with climate adaptation studies. Those interested in adaptation planning should keep track of devel- opments from the Federal Highway Administration (FHWA) and the Federal Transit Administration (FTA) of the U.S. DOT, both of which have funded important pilot studies on adapta- tion of the transportation system to a changing climate. The U.S. DOT has a climate change clearinghouse (http://climate. dot.gov/) as do groups such as the American Association of State Highway and Transportation Officials (AASHTO; http:// climatechange.transportation.org/), Georgetown University Climate Resource Center (http://www.georgetownclimate.org/ resources/transportation-and-climate-change-resource- center), the Center for Climate and Energy Solutions (http:// www.c2es.org/), and many others. The research design for this project consisted of an exten- sive literature review and the use of case studies to test the methods and approaches developed. For example, the diag- nostic framework that serves as the foundation for the study analysis was tested in three states—Michigan, North Caro- lina, and Washington. The benefit–cost methodology pre- sented in Appendix B of Part I, the Practitioner’s Guide, was based on project data obtained from these three states as well. In addition, this research benefited from parallel work spon- sored by the FHWA in the Gulf Coast 2 project, described in a later chapter.

124 2.1 Introduction This chapter describes the approach followed in conducting the research. Given the multidisciplinary nature of the topic, the research utilized expertise in transportation engineering/ operations, systems analysis, planning, climate science, policy, and construction/maintenance in a multi disciplinary research design. In particular, interaction with climate scientists was a critical factor in developing conclusions and recommenda- tions. The chapter also presents a conceptual framework of how the highway system is viewed and how this framework can then be used to identify potential climate change–related impacts. 2.2 Research Approach The research was conducted in six phases. Phase 1 identi- fied climate change–related stresses that could affect the U.S. highway system over the next 40 years. This phase included identifying region-specific stresses and impacts for a range of climate-related changes. So, for example, coastal regions will be affected by sea-level rise and storm surges while non- coastal states might be affected more by higher temperatures. The impacts could relate to how roads are designed, how road networks are operated, and how ecological mitigation strate- gies are defined and managed. The United States was divided into 10 climate regions that could be defined with different climate and extreme weather characteristics. Climate models were used in defining these regions. Phase 2 identified the current state of practice and knowl- edge in transportation adaptation planning through a litera- ture search and interviews with adaptation leaders around the world. This resulted in a synthesis of typical practices and strat- egies that were being considered in many different locations. Phase 3 developed a diagnostic framework that not only outlined the research steps that would be followed in this project, but also could be used in conducting adaptation planning for an agency. This phase also developed an evalua- tion approach for determining costs of adaptation strategies and understanding the expected benefits of implementing such strategies. The framework was applied to two of the regions identified in Phase 2. Phase 4 produced a guidebook on adaptation planning for practitioners (Part I of this volume) that was designed as a step-by-step approach to adaptation planning. In addi- tion, a prototype web-based decision support tool was devel- oped that allows users to identify those situations in which more design flexibility might be necessary to account for future climate-related risks [available on the Transportation Research Board (TRB) website: http://www.trb.org/Main/ Blurbs/169781.aspx]. A spreadsheet tool was also developed that could be used to conduct a benefit–cost analysis on dif- ferent adaptation actions at a particular location(available on the TRB website: http://www.trb.org/Main/Blurbs/169781. aspx). This phase also identified different institutional and organizational strategies for multijurisdictional collabora- tion and multiagency coordination. The final phase, Phase 5, recommended future research. 2.3 Conceptual Framework of the Highway System Prior to examining the probable impacts of climate change factors on highways (and opportunities for potential adapta- tion strategies), it is important to define what is meant by the highway system. A conceptual framework of the highway system helped guide the research tasks in terms of the types of impacts that might be expected from a changing climate as well as those elements of the highway system that might be at higher risk than others. The idea of a highway-related conceptual framework for climate adaptation is not new. This approach was used in the writing of the resource paper for TRB Special Report 290 in which the conceptual framework shown in Figure II.1 C H A P T E R 2 Research Approach and Conceptual Framework of the Highway System

125 was used to target potential components of road infrastruc- ture design that could be affected by changes in environmental conditions (Meyer 2008). This conceptualization was the basis for a matrix that then indicated expected changes in envi- ronmental conditions and the influence on the design of the road network. The concept shown in Figure II.1 was useful for this research, but it clearly needed to be expanded to include more than just a road segment and more than an interest in design since most of the highway system that will serve the next few generations is already built (and showing its age), and network-level land use patterns are largely set. For example, the intermodal con- nections that the road network serves are an integral part of the transportation system; a more “network-oriented” concept of the highway system is essential for conceptualizing this. Also the road right-of-way needs to be looked beyond because state DOTs are often involved in a range of activities (such as emer- gency response and environmental mitigation) that could be affected by changes in environmental conditions. Perhaps most importantly, the range of state DOT activities that will be affected by such changes needed to be defined in a systematic and comprehensive way. Road design is impor- tant, but so too are the transportation services essential for sustaining society as the full range of activities that constitute what a state DOT and other transportation agencies do to develop and manage a road network—including operations, maintenance, and construction—is considered. Three different frameworks were used to represent three scales of roadway design and operations that could be affected by climate change–related environmental stresses. The first is shown in Figure II.1 and represents a typical road segment. From the perspective of change in local environmental con- ditions due to changes in climate or weather, this representa- tion is perhaps the most useful. However, as noted previously, a much broader picture of the potential impacts of climate change on transportation services and agencies is needed. The second framework expands the road segment to a corridor perspective, one that includes “beyond the right-of-way” concerns, such as wetland mitigation issues and emergency response. The third framework presents a network perspec- tive, which expands the perspective even further to include system continuity of an already overtaxed and aging system as reflected in operations and maintenance policies and, from a physical network perspective, the connections between the road network and other components of the transportation system, such as intermodal terminals and stations. 2.3.1 A “Typical” Road Segment There are several components and design issues that are common to most transportation facilities, including roads and highways, rail lines, runways, and transit facilities. The five key components to the design of a typical road segment are subsurface/foundation conditions, materials specifications, structures, typical cross sections, and drainage/erosion. Each is discussed in the following paragraphs. Subsurface Conditions The stability of a built structure depends upon the soils on which it is built. Geotechnical engineers focus their attention on the properties of different soil types and their behavior given different design loadings (see, for example, Budhu 2000 and Coduto 1999). The expected behavior of soils directly influ- ences the design of foundations and support structures for the infrastructure itself. Various stresses act upon soil, including geostatic, horizontal, and shear stresses, as well as stress associ- ated with the weight of structures built on the soil. The design of foundations for transportation facilities reflects the soil condi- tions, water table, dead weight of the structure, and forces that add to the dynamic loads being placed on the structure (Reese et al. 2006). One of the important factors for subsurface design is the degree of saturation and expected soil behavior under saturated Source: Meyer (2008). Figure II.1. Assets of a typical road segment.

126 conditions. Changes in pore water pressure can have signifi- cant effects on the shear strength of soils, and in fact it is a change in soil shear strength that has caused many failures in ground slopes (e.g., mud slides). A good example of how subsurface conditions can affect design is the behavior of dif- ferent soils under seismic forces and the resulting effects on built structures. The shifting or liquefaction of soils during a seismic event creates significant risks of unstable soil condi- tions, and thus the destabilization of structures built on top of the soils. Seismic codes have been enacted in many regions of the world focused in particular on dealing with the chang- ing characteristics of foundation conditions during such extreme events (National Research Council 2003). Materials Specifications Transportation structures are constructed of materials selected for their performance under design loads and envi- ronmental conditions. Much of the original research in trans- portation during the 1940s and 1950s focused on improving the ability of materials to withstand the loads associated with transportation use while still remaining resilient in response to changes in environmental conditions. Transportation research engineers continue to improve the physical properties of both asphalt and concrete pavements. Pavements, as a transpor- tation facility component, affect facility performance at a considerably large spatial scale and their performance can change dramatically given changing conditions, such as heavier vehicles, higher traffic volumes, more dramatic freeze–thaw cycles, or subgrade soil dynamics (saturation, erosion, etc.). Construction materials have a significant influence on the design and performance of bridges as well. Steel, concrete, or timber bridges must each handle the dead weight and dynamic loads they will be subject to, and thus the strength and resiliency of the bridge materials become of paramount concern to the bridge engineer. In addition to the changing conditions men- tioned previously, the strength and protection of materials used in the design might have to be enhanced to account for expected wind loads, increased moisture or humidity (that could acceler- ate corrosion), and (for bridges located in coastal regions) more violent storm surges. Cross Sections and Standard Dimensions Given the complexity of designing a transportation facil- ity, and of all the subcomponents that it consists of, engi- neers often identify typical sections that are applicable to much of a given design corridor. A typical longitudinal cross section for the road shown in Figure II.1, for example, would show the depth of subgrade, pavement materials and thick- ness, width of lanes and shoulders, slopes of the paved sur- face, expected design of the area outside the paved surface, and other appurtenances that might be found in a uniform section of the road. As noted above, the type of pavement and design of the subgrade would reflect the environmental conditions found along the alignment. The slope of paved surface would be determined not only by the physical forces from the vehicles using the facility (e.g., superelevation), but also by the need to remove water from the paved surface. In areas where substantial precipitation would be expected, the slope of pavement might be slightly higher to remove water to the side of the road as soon as possible. Cross sections would also be developed for areas where designs would be different from the typical section, such as locations for culverts, special drainage needs, bridges, and other structures that would be close to the side of the road. The design of each of the key components of the cross sec- tion usually reflects design standards that have been adopted by the owner of the facility, such as a transportation agency. Thus, design manuals are often available with standards for lane and shoulder widths, transverse slopes, radii for road curvature, dimensions of barriers, merge and exit areas, cul- verts, drainage grates, signing, and pavement markings. Most of these standards are based on field or laboratory studies, many of which occurred decades earlier. Design criteria are also associated with such things as the vertical clearance over waterways and other roads. For exam- ple, the U.S. Coast Guard establishes vertical clearance guide- lines for bridges over waterways, with the vertical clearance dimensions depending on the type of navigation occurring on the river. One of the lessons learned from Hurricane Katrina was that the probabilistic vertical clearance designed into many of the Gulf Coast bridges over water channels was too low to withstand the actual storm surge that went over the bridge deck and floated the decks off of their supports. The bridges have been rebuilt with a higher clearance over the water surface along with improved fasteners to the bridge piers. Drainage and Erosion Water is one of the most challenging factors to design for in transportation engineering. As noted previously, saturated or near-saturated soils can be a critical consideration in the design of a facility’s substructure and foundations. In addi- tion, runoff from impermeable surfaces such as bridge decks or road surfaces must be handled in a way that redirects water flows away from the facility itself, but which does not harm the surrounding environment. Standard designs for drainage sys- tems, open channels, pipes, and culverts reflect the expected runoff or water flow that will occur given assumed magni- tudes of storms. Something as simple as the design of a cul- vert entrance would be affected by the assumed surge of water that would flow through it with due consideration for conse- quences of exceedances and construction costs vs. failure risks.

127 Structures In the context of this report, structures will primarily refer to bridges. Consistent with the previous discussion on how engineers account for different physical forces when develop- ing a design, civil engineering has a long history of research and practical experience with understanding how such forces act upon buildings and bridges [see Ellingwood and Dusenberry (2005) for an overview of how building codes have evolved over time in response to new types and degrees of structural loading]. The engineering design process is based on under- standing the likely loads or forces that will be applied to the structure (note the practice of assigning a factor that represents how important the bridge is) and developing a design that provides a level of resistance to these forces that will exceed expected loads. The current approach toward bridge design is to consider the inherent uncertainty in expected loads and resistance factors that a bridge will be exposed to, and thus probabilistic methods are used to incorporate such uncer- tainty. The primary focus of such an approach is to increase the reliability of the structure over its lifespan while con- sidering the economic costs of failure versus construction/ rehabilitation cost. AASHTO’s most recent bridge design manual incorporates risk into the calculations of bridge design parameters, although the economic costs of failure are not totally considered. Bridges over water present a special challenge to bridge engineers. According to the AASHTO LRFD Bridge Design Specifications (AASHTO 2004a), waterway crossings should be studied with respect to the following factors: • Increases in flood water surface elevations caused by the bridge • Changes in flood flow patterns and velocities in the chan- nel and on the floodplain • Location of hydraulic controls affecting flow under the structure or long-term stream stability • Clearances between the flood water elevations and low sections of the superstructure to allow passage of ice and debris • Need for protection of bridge foundations and stream chan- nel bed and banks • Evaluations of capital costs and flood hazards associated with the candidate bridge alternatives through risk assess- ment or risk analysis procedures As can be seen in this list, the assumed behavior of the water body below the bridge significantly affects how the design of the bridge proceeds. The design of bridges in coastal areas has received renewed attention given the experience with Hurricane Katrina. According to a position paper of the Fed- eral Highway Administration (FHWA 2005), “in the coastal environment, design practice assumes that flood events would essentially behave in a manner similar to a riverine environ- ment. However, bridge failure mechanisms associated with recent storm events have resulted in a re-evaluation of these assumptions. The result is a need to differentiate how FHWA considers the state of practice to hydraulically design bridges in the coastal environment.” As noted in the paper, the hur- ricane damage to the Gulf Coast bridges resulted primarily from the combination of storm surge and wave crests. How- ever, most state DOTs assume a riverine environment when designing bridges, which assumes a 50-year storm event (this approach is codified in state drainage manuals, AASHTO drainage guidance, and in FHWA floodplain regulations). The result of this assumed frequency of storm is that designs do not consider the effect of wave actions on the bridge. In other words, according to their own regulations and design guidelines, state DOTs can consider a storm surge, but not additional wave actions. As noted by the FHWA, “state DOTs find themselves in the position that their own regulations and guidelines do not per- mit them to consider alternative bridge design frequency crite- ria” (FHWA 2005). The FHWA recommended that a 100-year design frequency be used for interstates, major structures, and critical bridges that would consider a combination of wave and surge effects, as well as the likelihood of pressure scour during an overtopping event (water levels going over the structure). The consideration of a super flood frequency surge and wave action (that is, the 500-year design frequency) was also sug- gested. It was also recommended that risk and cost assessments be conducted. Note that the marginal costs of additional safety factors must also be kept in mind. Long-span bridges, especially over water, present a special challenge in two respects. First, very long bridges have to account for wind forces, which can be quite substantial in areas where the topography results in a “canyon effect,” that is, high hills or cliffs that concentrate and thus make more powerful the winds striking the bridge. For suspension or cable-stayed bridges, these wind forces must be accounted for in the design strength of the support structure and in the level of deflection or flexibility designed into the bridge itself (Simiu and Scanlan 1996). For long-span bridges, engineers conduct wind tunnel tests of different sections of a proposed design to assess section behavior under varying wind conditions. Second, columns or piers that are located in water are sub- ject to scour, that is, the erosion of the river or stream bed near the column foundation. The majority of bridge failures in the United States are the result of scour (AASHTO 2004a) in that the flow of water currents at the column base can erode the stability of the column foundation. The FHWA requires that bridge owners evaluate bridges for potential scour associ- ated with the 100-year event (known as the base flood) and to check scour effects for the 500-year event (known as the super flood). If floods or storm surges were expected to occur more

128 frequently or channel flows were to become more turbulent, the engineer would potentially have to rethink the design of such foundations (Sturm 2001). The foregoing description of the different components of a typical roadway segment does not cover all of the different considerations that would enter into the design thought pro- cess of the engineer. However, it does illustrate the important influence of standards and guidelines in the design process in response to expected environmental factors. In addition, the discussion suggests some of the design categories in response to changes in these environmental conditions, and in particu- lar those related to climate change, and their implications as to how engineers should design a transportation facility. 2.3.2 A Corridor Perspective The potential impacts of changing environmental condi- tions due to climate change on a typical road segment would of course accumulate over a corridor and throughout the net- work where similar circumstances exist. At the corridor level, disruptions to passenger and freight movements could be significant if such disruptions occur over a long period (e.g., bridge collapse) and/or if very few alternative routes exist. The impacts of many of the weather-related disruptions that have occurred in recent years—Midwestern floods and correspond- ing impacts on Interstate highways and mail rail lines, Wash- ington State floods and closure of Interstate 5, drought and corresponding wildfires and closure of Interstates in Colorado, and flooding and highway/rail closures in Vermont—have been primarily felt at the corridor level. By affecting corridor mobil- ity and accessibility, weather-related disruptions have effects on through traffic (and thus economic impacts beyond the cor- ridor) as well as on corridor-level traffic that have origins and destinations within the corridor (and thus economic impacts in adjacent communities). With respect to environmental conditions, if subsurface conditions are affected because of changes in soil moisture in one location, there is a strong possibility that this effect will be found in many other parts of a network, or certainly within a corridor (where similar soil conditions could be expected). Figure II.2 illustrates other types of concerns that might be found within a road corridor over and above those Figure II.2. Corridor-level impacts of changing local environmental conditions.

129 related to specific design components. Most of these concerns relate to either maintenance practices or environmental miti- gation and/or avoidance strategies. Outside-of-Right-of-Way Environmental Mitigation Many transportation agencies have developed environmen- tal mitigation programs that focus on replacement assets out- side of a corridor’s right-of-way. An example of this includes the concept of wetland banking for wetlands that are disturbed as part of a construction process. With changing environmen- tal conditions due to long-term climate change, the ability to develop ecologically sound and functionally replicating eco- logical mitigation strategies could be seriously hindered. For example, some state DOTs are currently taking into account projected sea-level rise when identifying wetland mitigation sites as many of the previous wetland mitigation sites have been located in estuaries that are likely to be impacted by sea- level rise. Erosion, Drainage, and Runoff Impacts Changes in precipitation, both overall levels and rainfall intensities, are considered two of the major changes likely to be experienced in the future. The design implications of these changes to such things as culverts and road-related drainage systems were discussed in the previous section. The impact noted here is the likelihood of increased runoff and erosion impacts on surrounding land uses and ecological resources. Increased runoff, with higher volumes and perhaps higher intensities, could have significant impacts on nearby water bodies, such as streams and rivers. Such a possibil- ity might require new means of handling erosion and run- off, primarily by reducing volumes or diverting flows away from sensitive areas. Right-of-Way Maintenance Studies overseas have identified changing right-of-way main tenance operations as one of the potentially impor- tant impacts of changes in climate on transportation agency practices. These impacts could relate to changes in grow- ing season (and thus more or less mowing), invasive species infestation, snow removal, and flooding caused by backed up drainage systems. Synergistic effects of climate change such as unseasonable freezing rain on trees already weakened by increased predation from invasive species could contribute to widespread power outages and road closures in the wake of storm events. It will be difficult to predict a specific point in time when such issues might become a serious concern to a transportation agency. More likely, changes in maintenance practices will be phased in as “emergencies” become more “routine,” and it becomes apparent that current approaches are no longer meeting the needs of the highway system. Construction Practices and Activities Changes in temperature and precipitation and the cor- responding need to utilize different construction materials could affect construction practice. In addition, a lengthening or shortening of the construction season could also influence a transportation agency’s construction program. Transpor- tation agency adaptation plans from overseas identify an increasing frequency of more intense storms as affecting con- struction costs and scheduling, as well as the need to provide improved training to construction workers who might have to work more often in inclement weather. 2.3.3 A Network Perspective The final perspective on potential climate change impacts on the highway system relates to the overall management of the highway network, including building and protecting the agency’s assets as well as developing system management strategies for expected disruptions (see Figure II.3). Alternate Routes and Corresponding System Operations Strategies One of the likely characteristics of future weather condi- tions is more intense storms (or extreme events as they are called in the literature) and a corresponding disruption to the highway network. The impacts of Hurricanes Katrina and Sandy on all aspects of a region’s transportation network, including highways, transit facilities/services, airports, ports, and freight terminals, have been well documented. Responses to events such as these will require strategic and coordinated response plans to not only deal with the immediate after- math, but also help speed the recovery process. In metropoli- tan areas, in particular, where traffic management centers have been established to coordinate and guide traffic flows, it is likely that such centers will be used more frequently to respond to weather-related events and that improved emer- gency response systems including 511 Traveler Information systems be developed and deployed as part of an overall adap- tive management strategy. Vermont’s experience after Tropi- cal Storm Irene of establishing such coordination centers and using Google maps and information sources was one of the lessons learned (VTrans 2012b). Intermodal Connections Although this project is focused on the “highway sys- tem,” in reality today’s transportation system consists of

130 interconnections among different modes serving a variety of purposes. Examples of such interconnections include inter­ modal passenger and freight terminals, park and ride lots, access roads to freight intermodal facilities, and pedestrian/ bicycle facilities connecting to transportation stations or ter­ minals. Even though a transportation agency might not have jurisdiction over intermodal facilities, it makes sense for some­ one to view the facility and the access to the facility as one part of a larger system. Strategies to protect road access should be combined with strategies to protect the facility itself and main­ tain vital transportation services in a “just in time delivery” economy. Location Engineering (where to put the facility to begin with) Designs for new or relocated transportation facilities always include location studies to determine where to build the facility. Such efforts are often associated with much broader environmental impact analyses that examine a range of alternative alignments and design characteristics. Location studies themselves often do not have specific design criteria associated with where facilities will be located, although fac­ tors such as right­of­way width, roadway curve radii, and vertical slope limitations for different types of facilities will constrain designs to certain design footprints. In addition, as part of environmental analyses, a fatal flaw analysis often identifies areas or sites so environmentally sensitive that the designer will stay clear of these locations. The important question with respect to transportation facility location stud­ ies is how areas that might be susceptible to climate change effects, such as coastal or low­lying areas, might be evaluated for suitability. Building and Protecting Agency Assets Transportation agencies are often owners of a substan­ tial number of buildings, shelters, and other physical assets used by employees in the day­to­day operations of the agency. Although such assets are not often considered in most adap­ tation studies, which tend to focus on the transportation network itself, agency managers will have to deal with man­ aging such assets with changing local environmental con­ ditions. This could mean developing strategies ranging from enhanced protection from wider temperature ranges to protec­ tion from inundation. It is likely that as climate and weather conditions change, the building industry will change with it, including the use of innovative materials to better han­ dle new loads and stresses on the structures. So, in such cases, these changes will be incorporated into building and materials specifications. However, especially in the case of state transportation agencies, which have buildings spread Figure II.3. Network-level impacts of changing local environmental conditions.

131 out over an entire state, the need to be cognizant of changing local environmental conditions and their potential impact on the agency’s assets could be an important concern to future managers. 2.4 Summary This chapter presented a multilevel perspective on poten- tial impacts of climate change on the built and yet-to-be- built highway system. Each level examines a particular scale of application and in many ways can be viewed as adding a more complex and strategic management role. For example, many of the design changes that might be necessary at the typical road-segment level can be incorporated into design standards and agency standard operating procedures. How- ever, dealing with system-wide operations strategies or a more comprehensive management of an agency’s physical assets would imply a higher level of management involve- ment to deal with an already built, increasingly congested, and aging system.

132 3.1 Introduction The Intergovernmental Panel on Climate Change (IPCC) Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation discussed how combining knowledge about climate science, disaster man- agement, and adaptation can inform discussions about man- aging the risks of extreme events and disasters in a changing climate (IPCC 2012). It included a wide range of options used by organizations to reduce exposure and vulnerability, and improve resilience to climate extremes. The report also made a number of observations about likely extreme climate-related events in the 21st century, including increases in the frequency of heavy precipitation; increased frequency of warm daily temperature extremes; decreases in cold extremes; increases in heat wave length, frequency, and intensity; increases in wind speeds of tropical cyclones; droughts intensifying in central North America; upward trends in extreme sea levels; and the projected precipitation and temperature changes that imply changes in floods. The report further suggested that approaches to climate change adaptation and disaster risk management can be complementary and effectively combined, as well as comple- ment other community goals. For example, such efforts can help “address development goals, improve livelihoods and human well-being” (IPCC 2012). These so-called “no or low regrets” measures include early warning systems, land use planning, sustainable land management, and ecosystem man- agement. These measures help reduce vulnerability to pro- jected changes in climate and also tackle underlying drivers of change in extreme weather or climate. These measures are typically recommended when uncertainties over future cli- mate change directions and impacts are high. For example, continued maintenance of existing transportation infrastruc- ture to minimize the chances of flooding or other damage that might occur will help prepare agencies before more perma- nent adaptation plans can be implemented. As suggested by this report, adaptation planning and adap- tive management is a relatively new concept, especially in the United States. Table II.1 presents the results of a recent review of climate change adaptation frameworks that have been generally applied to all sectors and those that have focused on transportation (Wall and Meyer 2013). This review sum- marized the current limitations and barriers to further devel- opment that characterized many of these efforts as being: “(1) data limitations—limited or inaccessible infrastructure data; limited usable climate data; (2) an inadequate treatment of risk—reconciling the immediate need for action with the perception of distant consequences; the qualitative treatment of risk; defining acceptable levels of risk; and (3) the lack of sufficient financial resources. Transportation agencies and organizations—particularly independent and private sector organizations—identified additional limitations or barriers: (4) interdependencies and regulatory barriers and (5) uncer- tainty in future system demand that causes uncertainty in the need for adaptation.” The following sections review adapta- tion practices and methodologies that have been tried in practice in both the United States and internationally. 3.2 U.S. Perspectives 3.2.1 Federal Government Much of the focus of federal efforts at transportation and adaptation has been on the activities of federal agencies them- selves. The Council on Environmental Quality (CEQ) has issued “Instructions for Implementing Climate Change Adap- tation Planning in Accordance with Executive Order 13514.” The Executive Order requires each federal agency to evalu- ate agency climate change risks and vulnerabilities to manage both the short- and long-term effects of climate change on the agency’s mission and operations. A climate change adaptation policy was adopted by the U.S. DOT in 2012 that mandated the integration of climate change impacts and adaptation into C H A P T E R 3 Current Practice in Adaptation Planning and Adaptive Management

133 Framework General Infrastructure Country Agency/Organizaon Climate Change Risks to Australia’s Coast: A First Pass Na onal Assessment Australia Department of Climate Change (2009) Climate Change Risks for Coastal Buildings and Infrastructure: A Supplement to the First Pass Na onal Assessment Australia Department of Climate Change and Energy Efficiency (2011) Infrastructure and Climate Change Risk Assessment for Victoria Australia Victorian Government (CSIRO et al. 2007) Adap ng to Climate Change: Canada's First Na onal Engineering Vulnerability Assessment of Public Infrastructure Canada Public Infrastructure Engineering Vulnerability Commiee (PIEVC), Engineers Canada (2008) PIEVC Engineering Protocol for Climate Change Infrastructure Vulnerability Assessment Canada PIEVC, Engineers Canada (2009) Adap ng to Climate Change: A Risk Based Guide for Ontario Municipali es Canada Ontario Ministry of Municipal Affairs and Housing (Bruce et al. 2006) Adapng to Climate Change: A Risk Based Guide for Local Governments Canada Natural Resources Canada (Black et al. 2010) Ahead of the Storm: Preparing Toronto for Climate Change Canada Toronto Environment Office (2008) Climate Change Risk Management Strategy for Halifax Regional Municipality Canada Halifax Regional Municipality (Dillon Consulng and de Romilly & de Romilly 2007) The Naonal Flood Risk Assessment Scotland Scosh Environmental Protecon Agency (SEPA) (2011a) Flood Risk Management Strategies and Local Flood Risk Management Plans Scotland Scosh Environmental Protecon Agency (2011b) Climate Change Adaptaon in New York City: Building a Risk Management Response United States New York City Panel on Climate Change (2010) Preparing for Climate Change: A Guidebook for Local, Regional, and State Governments United States King County (WA) Execuve (Center for Science in the Earth System and King County 2007) Impact of Climate Change on Road Infrastructure Australia Austroads (Norwell 2004) Risk Management for Roads in a Changing Climate (RIMAROCC) European Union ERA NET (Bies et al. 2010) Climate Change Uncertainty and the State Highway Network: A Moving Target New Zealand Transit New Zealand (Kinsella and McGuire 2005) [now NZ Transport Agency] Climate Change Effects on the Land Transport Network Volume One: Literature Review and Gap Analysis New Zealand NZ Transport Agency (Gardiner et al. 2008) Climate Change Effects on the Land Transport Network Volume Two: Approach to Risk Management New Zealand NZ Transport Agency (Gardiner et al. 2009) Scosh Road Network Climate Change Study Scotland Scosh Execuve (Galbraith et al. 2005) Scosh Road Network Climate Change Study: Progress on Recommendaons Scotland Transport Scotland (Galbraith et al. 2008) Scosh Road Network Landslides Study Scotland Scosh Execuve (Winter et al. 2005) Adaptaon Reporng Powers received reports* United Kingdom Department of Environment, Food and Rural Affairs (2012) Table II.1. General and transportation infrastructure-specific adaptation frameworks. (continued on next page)

134 the planning, operations, policies, and programs of the agency (U.S. DOT 2011). The policy statement also directed the U.S. DOT modal administrations to encourage state, regional, and local transportation agencies to consider climate change impacts in their decision making. The CEQ also proposed draft guidance in 2010 on how cli- mate adaptation could be considered as part of the National Environmental Policy Act (NEPA) process (CEQ 2010). The draft guidance recommended that climate change stressors should be considered for projects that have long useful lives or that are located in areas that are considered vulnerable to specific effects of climate change (such as increasing sea level or ecological change). The draft guidance proposed to use the scoping process to establish the degree to which “aspects of cli- mate change may lead to changes in the impacts, sustainability, vulnerability, and design of the proposed action and alterna- tive courses of action.” The NEPA requirement to describe the “affected environment” of a proposed action that might have significant impact was pointed to as the most logical step in the process where observed and projected effects of climate change should be considered. Once the relevant climate stress- ors are identified, the agency can then determine the extent to which any proposed action will be affected by such change or the degree to which the action might exacerbate the likely impact. This includes not only the potential impact on the surrounding environment, but also the effects on vulnerable populations and nearby communities. The draft guidance suggests that climate change can affect the environment of a proposed action in a variety of ways— affecting the integrity of a project by exposing it to a greater risk of extreme conditions (e.g., floods, storm surges, or higher temperatures); increasing the vulnerability of a resource, eco- system, or human community; and possibly magnifying the damaging strength of certain effects. As of the date of this report, this guidance has not been finalized. Within the U.S. DOT, the activities of the FHWA and the FTA have been notable in fostering a leadership position on transportation adaptation. The FHWA began its involve- ment by hosting a peer workshop on adaptation in December of 2008 that involved metropolitan planning organization (MPO) and state DOT officials interested in climate adapta- tion. The workshop concluded by calling for a national adap- tation strategy and for the FHWA and other federal agencies to provide relevant and actionable guidance, research, and policy documents on the topic (ICF International 2012). The FHWA followed through by releasing a literature review, high- level climate data by U.S. regions, and a conceptual model to assess the vulnerability of transportation infrastructure to climate change. This model was pilot tested in five locations from 2011 to 2012 (see the text box for reports on these pilot studies), and the conceptual model was modified to reflect the lessons learned from the pilot studies (FHWA 2012a; see Figure II.4). In addition, FHWA initiated a major study on the impacts of climate change on transportation systems and infrastruc- ture in the U.S. Gulf Coast. Phase I of this study examined the likely climate change in temperature, precipitation, sea-level rise, and storm surge along with impacts on highway, water, air, rail, and transit modes in the Gulf Coast states (i.e., Texas, Louisiana, Mississippi, and Alabama) and identified adapta- tion measures. The study discussed four major conceptual factors to consider with respect to transportation-related Framework General Infrastructure Country Agency/Organizaon Climate Change Adaptaon Strategy United Kingdom Highways Agency and Parsons Brinckerhoff (2008) Climate Change Adaptaon Strategy and Framework United Kingdom Highways Agency (2009) Highways Agency Climate Change Risk Assessment United Kingdom Highways Agency (2011) Assessing Vulnerability and Risk of Climate Change Effects on Transportaon Infrastructure: Pilot of the Conceptual Model** United States Federal Highway Administraon (2012c) Climate Change & ExtremeWeather Vulnerability Assessment Framework United States Federal Highway Administraon (2012b) * Twenty-three agency reports were reviewed under the Department of Environment, Food and Rural Affairs reporng powers requirement. A full agency list can be found at hp://www.defra.gov.uk/environment/climate/sectors/reporng-authories/reporng-authories-reports/ ** This includes five pilot-program case study reports: Metropolitan Transportaon Commission et al. (2011), North Jersey Transportaon Planning Authority (2011), Oahu Metropolitan Planning Organizaon (SSFM Internaonal 2011), Virginia DOT (2011), Washington DOT (Maurer et al. 2011) Source: Wall and Meyer (2013) Table II.1. (Continued).

135 Source: FHWA (2012a) Figure II.4. FHWA’s Climate Change & Extreme Weather Vulnerability Assessment Framework. climate concerns—exposure to climate stressors, asset vul- nerability to these stressors, asset resilience, and adaptive capacity. It also examined how transportation agencies can incorporate climate change considerations into transporta- tion decision making. Phase II, starting in 2011, is focusing on Mobile, Alabama, by conducting an adaptation assessment and engineering analysis of potential adaptation strategies. A goal of this phase is to make this adaptation process repli- cable, so that other regions can conduct similar assessments (FHWA 2012a). The FTA has sponsored seven pilot projects that will exam- ine different adaptation strategies that were to fit within the transit agency’s structure and operations. Two of the pilot projects will demonstrate the integration of climate impacts with an asset management system. These pilot studies will provide practical experience with how a transit agency can consider climate change-related adaptation strategies in day- to-day operations (FTA 2013). Perhaps the most impactful federal adaptation policy has been issued by the U.S. Army Corps of Engineers (USACE). In this policy, the planning, engineering, designing, operating, and maintenance of Corps infrastructure must be sensitive to sea-level change and “must consider how sensitive and adapt- able (1) natural and managed ecosystems and (2) human and engineered systems are to climate change and other related global changes” (USACE 2011). Corps engineers are to define alternatives that are formulated and evaluated for a range of possible future rates of sea-level change, represented by “low,” “intermediate,” and “high” sea-level change scenarios, both “with” and “without” project conditions. In addition, they are to determine “how sensitive alternative plans and designs are to these rates of future local mean [sea-level change], how this sensitivity affects calculated risk, and what design or opera- tions and maintenance measures should be implemented to minimize adverse consequences while maximizing beneficial effects.”

136 The policy suggests multiple approaches for comparing and selecting desirable alternatives, including: 1. Use a single scenario and identify the preferred alterna- tive under that scenario. Then evaluate this alternative’s performance with other scenarios to determine overall performance. 2. Compare all alternatives against all scenarios. This approach does not necessarily result in the “best” alternative for a particular scenario, but rather allows one to be selected that is “more robust in the sense of performing satisfacto- rily under all scenarios.” 3. Modify the results of approaches 1 or 2 to incorporate alter- native features that improve overall life-cycle performance. 4. Explicitly consider uncertainty, and how sea-level change scenarios affect risk levels. 3.2.2 State Governments Many state governments developed Climate Action Plans in the mid- to late 2000s as a means of primarily assessing green- house gas reduction strategies. Very few discussed adaptation as a challenge facing government agencies. For those trans- portation agencies that have considered adaptation concerns, most efforts are in the early stage of identifying the major climate drivers, risks and vulnerabilities, and high-level adap- tation strategies. Only a handful of agencies have implemented adaptation actions. Where such efforts have occurred, they are described in the following sections. It is interesting to note that almost all of the U.S. leaders in adaptation are in coastal locations, presumably in response to the risks presented by sea-level rise and storm surge. Alaska The Alaska Department of Transportation and Public Facili- ties is in an unusual position in that its program includes non-transportation public facilities, giving it a wider jurisdic- tion than most DOTs. Among its concerns are communities that are in jeopardy of accelerated coastal erosion from winter storms due to lack of protective sea ice. Several of these com- munities developed relocation plans. As a result, much of the DOT’s adaptation activities focus on shoreline protection and relocation. One airport whose runway was directly threatened by coastal erosion has already been relocated. An USACE proj- ect has armored the shoreline of one of the communities as well. In addition, the Alaska Department of Transportation and Public Facilities has dedicated funding to combat perma- frost thawing under highways and is also actively working on drainage improvements and evacuation routes and shelters. References for the FHWA Pilot Studies on Climate Change Vulnerability Metropolitan Transportation Commission, Caltrans, and Bay Conservation and Development Commission, Adapting to Rising Tides: Transportation Vulnerability and Risk Assessment Pilot Project: Briefing Book, November 2011. http://www.mtc. ca.gov/planning/climate/Rising_Tides_Briefing_Book.pdf New Jersey Transportation Planning Authority, Climate Change Vulnerability and Risk Assessment of New Jersey’s Transportation Infrastructure, April 2012. http:// www.njtpa.org/Plan/Element/Climate/documents/CCVR_REPORT_FINAL_4_2_12_ ENTIRE.pdf Oahu Metropolitan Planning Organization, Transportation Asset Climate Change Risk Assessment, November 2011. http://www.oahumpo.org/climate_change/ CC_Report_FINAL_Nov_2011.pdf University of Virginia and Virginia Department of Transportation, Assessing Vul- nerability and Risk of Climate Change Effects on Transportation Infrastructure, Hampton Roads, VA Pilot, November 2011. http://www.virginia.edu/crmes/fhwa_ climate/iles/finalReport.pdf Washington State Department of Transportation, Climate Impacts Vulnerability Assessment, November 2011. http://www.wsdot.wa.gov/NR/rdonlyres/ B290651B-24FD-40EC-BEC3-EE5097ED0618/0/WSDOTClimateImpactsVulnerability AssessmentforFHWAFinal.pdf

137 California In response to a gubernatorial executive order, the California Department of Transportation (Caltrans) developed guide- lines for considering sea-level rise in project planning docu- ments (Caltrans 2011). As noted in the guidance, not only will enhancing the design features of structures likely be a consid- eration, but so too will be increasing costs for permit fees and mitigation. A three-part screening process was recommended, in essence answering the following questions: 1. Is the project located on the coast or in an area vulnerable to sea-level rise? 2. Will the project be impacted by the stated sea-level rise? 3. Is the design life of the project beyond year 2030? If it is determined that sea-level rise needs to be considered as part of the design, the project initiation document must provide a detailed discussion of potential impacts and how they might affect the design. California, Oregon, and Washington Although not a state study, the National Research Coun- cil was requested by California, Oregon, and Washington to investigate sea-level information at state, national, and global scales to determine coastal vulnerability and response to sea-level rise; to improve models and forecasts; to develop research priorities; and to develop decision support tools for a variety of users, including the USACE, which needs sea- level information to guide water resource investment deci- sions (National Research Council 2012). Global mean sea level is rising primarily because global temperatures are rising, causing ocean water to expand and land ice to melt. However, sea-level rise is not uniform. Sea- level rise along the coasts of California, Oregon, and Wash- ington depends on the global mean sea-level rise and also on regional factors, such as ocean and atmospheric circulation patterns in the northern Pacific Ocean, the gravitational and deformational effects of land ice mass changes, and tectonics along the coast. The projections show that for California south of Cape Mendocino the sea level is expected to rise because of land sub- sidence in California, but to the north sea level will decrease because of land uplift in Oregon and Washington. For the California coast south of Cape Mendocino, the study projects that sea level will rise 1.6 to 12 inches (4–30 centimeters) by 2030 relative to 2000, 4.7 to 24 inches (12–61 centimeters) by 2050, and 16.5 to 66 inches (42–167 centimeters) by 2100. For the Washington, Oregon, and California coasts north of Cape Mendocino, sea level is projected to change between -1.6 inches (-4 centimeters) (sea-level fall) and +9 inches (+23 centimeters) by 2030. The combination of land uplift and gravitational and deformational effects reduces the threat of future sea-level rise for Washington and Oregon. However, the land is rising along the Washington and Oregon coasts likely because inter-seismic strain is building in the Cascadia Subduction Zone. A great earthquake (magnitude larger than 8 on the Richter Scale), which has occurred in the area every few hundred to 1,000 years, would cause some coastal areas to immediately subside and relative sea level to suddenly rise. If this occurs, relative sea level could rise an additional meter or more over projected levels. Most of the damage along the California, Oregon, and Washington coasts is caused by storms—particularly the confluence of large waves, storm surges, and high astronomi- cal tides during a strong El Niño. The water levels reached during these large, short-term events have exceeded mean sea levels projected for 2100, so understanding their additive effects is crucial for coastal planning in this area. Maryland In January 2011, the Maryland Commission on Climate Change produced the Comprehensive Strategy for Reducing Maryland’s Vulnerability to Climate Change, Phase II: Build- ing Societal, Economic, and Ecological Resilience (Boicourt and Johnson 2010). Whereas Phase I established the background on sea-level rise, this report developed sector-based adapta- tion strategies. Transportation is included with “Population Growth and Infrastructure.” One of the key policy recom- mendations requires state agencies to integrate climate change adaptation strategies into policies and programs. The report also called for the Maryland DOT to: • Conduct a comprehensive analysis of the vulnerability of Maryland’s infrastructure, • Assess the economic costs resulting from severe weather events, • Develop operation contingency plans for critical infra- structure, • Identify investment needs to prepare for future weather emergencies, and • Address funding and revenue constraints for current and future infrastructure needs. Maryland is one of the first states to begin systematically inventorying the vulnerability of its transportation assets to climate change, beginning with vulnerability to sea-level rise. Sea-level rise is an initial priority for Maryland’s adaptation plan because of that state’s particular vulnerability—it has more than 4,000 miles of coastline, much of it low-lying land on the Chesapeake Bay at risk to inundation (in fact, in the past century several islands in the Bay have disappeared under the

138 rising water levels). The state has developed a high-resolution LIDAR data set to allow development of sea-level rise inunda- tion models along its coastlines. Maps have been created for 14 coastal counties, depicting lands at potential risk. In 2013, Maryland’s governor signed an executive order, Climate Change and Coast Smart Construction, to increase the state’s long-term resiliency to storm-related flooding and sea- level rise. The executive order directed all new and reconstructed state structures, as well as other infrastructure improvements, be planned and constructed to avoid or minimize future flood damage. In particular, the state’s Department of General Ser- vices was directed to update its architecture and engineering guidelines to require new and rebuilt state structures to be ele- vated 2 or more feet above the 100-year base flood level. New York New York State has conducted a state-level assessment of climate change impacts specifically designed to assist in the development of climate adaptation strategies (New York State Energy Research and Development Authority 2011). It fore- casts climate change by regions of the state and acknowledges the need to plan for and adapt to climate change impacts in a range of sectors including transportation. Strategies include doing engineering-based risk assessments of assets and opera- tions. Other strategies include the protection of coastal trans- portation infrastructure with levees, sea walls, etc.; relocation of critical systems to higher ground; lengthening airport run- ways; using heat-resistant construction materials; and chang- ing engineering specifications related to climate. New York’s updated adaptation assessment steps are shown in Figure II.5. 3.2.3 Regional/Local Governments Asheville, North Carolina The French Broad River MPO, the regional planning agency for Asheville, North Carolina, was one of the first MPOs in the United States to incorporate climate change considerations into its long-range transportation plan. The adaptation plan- ning approach focused on climate variability that was likely to occur in the region and system vulnerability and resiliency (French Broad River MPO 2010). For example, the plan noted that in its study area, which is primarily mountainous and full of forests, extended drought increases the danger of wildfires and their associated smoke hazard, while the intense storms and increased rainfall increase the occurrence of flooding, landslides, and dam breaches. From an analysis of expected climate extremes and locations of key transportation facilities, the hottest locations in the study area are in the valleys where major transportation corridors were located, and the coldest locations were in the mountains. Therefore, the plan noted that “roads in the valleys will need to be designed to withstand greater periods of extreme heat, while the roads in the higher Source: New York State Energy Research and Development Authority (2011) Figure II.5. New York State adaptation assessment steps.

139 elevations will need to be designed to withstand colder temper- atures and icing events.” The types of climate change–related impacts anticipated in the region include the following: 1. Increase in flooding occurrence and intensity, especially tied to severe storms. This increased flood intensity will affect many bridges and large sections of key transporta- tion arteries. 2. Increase in landslides due to severe storms and continued road building associated with steep slope development. Increased rain is a trigger for an increasing number of landslides. 3. Wildfire/smoke impacts due to more intense periods of drought. 4. Dam breach analysis should be performed and early warn- ing systems created for all major dams in the area that are up dip from major transportation corridors. 5. Staging areas for fuel supplies should be strategically placed based on these hazards. There is a relatively modest amount of local fuel storage, and many of these locations are in floodplains. The analysis process was straightforward; proposed long- range transportation plan projects were overlaid on maps of the region’s 500-year floodplain, wildfire risk, and steep slopes (prone to landslides). Figure II.6, for example, shows study area highways that are located in the 500-year storm floodplains. By following this approach, projects that had beneficial impacts Source: French Broad River MPO (2010). Figure II.6. Identifying vulnerable highway facilities, Asheville, North Carolina.

140 for climate adaptation over and above the benefits associated with the project justification process were indicated on the prioritization list. King County, Washington King County developed its Preparing for Climate Change: A Guidebook for Local, Regional, and State Governments in conjunction with its Climate Plan (Center for Science in the Earth System and King County 2007). The County formed an interdepartmental climate change adaptation team, part- nering with the Climate Impacts Group at the University of Washington, for scientific expertise. Each year, the Executive Action Group is required to produce a report that provides updates on the county’s climate planning. Actions already underway by King County Road Services Division include evaluation of higher flows on bridge and culvert design as well as seawall modifications. The Road Ser- vices Division is rebuilding over 57 bridges and 40 culverts to improve stream flows and endure the most significant impacts of climate change. Houston The Houston–Galveston Area Council formed the Fore- sight Panel on Environmental Effects in 2007 to assess possible climate change impacts in the Houston region. In 2008, the panel produced the Foresight Panel on Environmental Effects Report that highlighted its findings. The report, piggybacking on data from the FHWA’s Gulf Coast Study, outlined projected climate changes for the Houston metro area and their impacts on infrastructure, public facilities, ecosystems, and public health. A geographic information system (GIS)–based study of sea-level rise and flooding scenarios helped to illustrate vulnerable infrastructure and facilities. New York City In New York City, the climate adaptation effort grew directly out of the release of the report PlaNYC: A Greener, Greater New York, which recommended the formation of an inter- governmental task force, a plan to protect communities at high risk from climate impacts, and an overall adaptation planning process. The following year, Mayor Bloomberg formed the Climate Change Adaptation Task Force to address infrastructure vulnerabilities and also the New York City Panel on Climate Change to function as a technical advisory com- mittee on developing city-specific climate change projections and assist in new infrastructure standards. New York requires annual performance reports on established indicators. The Port Authority of New York and New Jersey has also been very active in addressing climate adaptation, by implementing guidance to consider the impacts of climate change, raising the flood plain elevation, and even implementing some strate- gies in projects. Climate projections were downscaled to the New York City region by applying the projected changes from the relevant grid box to observed climate data. In addition, because there has been controversy over the IPCC 2007 sea-level rise predic- tions, which did not include melting of the Greenland and Antarctic ice sheets, the New York scenarios included an addi- tional sea-level rise scenario that corresponded to more rapid ice melt. New York City’s risk-based approach to adaptation, “Flexible Adaptation Pathways,” is an iterative process that rec- ognizes the multiple dimensions of climate hazards, impacts, adaptations, economic development, and other social factors. This iterative process is predicated on the establishment of cli- mate change monitoring programs that can provide feedback to the process to allow for changing “pathways.” Most recently, in response to Hurricane Sandy (2012), New York Governor Mario Cuomo established several commis- sions to investigate the lessons learned from the massive dev- astation to infrastructure caused by the storm in New York City. The commission focusing on infrastructure predicted that the state would experience more frequent floods, storm surges, heat waves, and droughts. In preparation, the com- mission recommended that transportation infrastructure be designed to be more resilient to such environmental condi- tions and that better preparation occur in protecting existing infrastructure. New York City prepared a plan that outlined specific actions that should be taken to provide a more resil- ient infrastructure to future extreme weather events (New York City 2013). Punta Gorda, Florida The City of Punta Gorda, Florida, inserted an adaptation component into the city comprehensive plan as well as its Com- prehensive Conservation and Management Plan in 2008. It has adopted comprehensive plan language to address the impacts of sea-level rise and seeks strategies to combat its effects on the shoreline of the city. Punta Gorda developed its adaptation plan in partnership with the U.S. Environmental Protection Agency (EPA), as part of EPA’s Climate Ready Estuaries Program (Southwest Florida Regional Planning Council 2009). The approach taken by the City of Punta Gorda, Florida, represents an advanced approach for a small city (no doubt in part because of its participation in EPA’s Climate Ready Estu- aries Program, which provided additional technical support). For the plan, critical facilities of all types were identified. For transportation, this consisted of a list of all bridges in the city; no other transportation facilities were singled out as critical facilities. Infrastructure costs, based on estimates prepared for a previous Federal Emergency Management Agency (FEMA)

141 disaster preparedness plan, were used to estimate losses from storm flooding (based on the facility’s location in flood zones). To assess risk and vulnerability of critical infrastructure to vari- ous climate effects, rather than conduct a quantitative engi- neering analysis of the infrastructure, Punta Gorda turned to a stakeholder and public involvement approach. At a series of public meetings, stakeholders and the public engaged in exer- cises to identify and prioritize areas of vulnerability and to rec- ommend preferred adaptation strategies. 3.3 International Perspectives Eleven adaptation studies from four countries (United King- dom, Australia, Canada, and Norway) were reviewed for this project. These countries were chosen because they are consid- ered leaders in climate change adaptation practice and they have extensive literature available in English. Before discuss- ing the specific studies, it is useful to have an understanding of the different contexts in which the various plans were created. For three of the countries studied (Australia, Canada, and the United Kingdom), a brief summary of the national perspective overarching these plans is provided. 3.3.1 Overview of National Climate Change Policies Australia In Australia, mitigation and adaption are managed under the same government agency—the Department of Climate Change and Energy Efficiency. The government’s climate change policy rests on three actions (Commonwealth of Aus- tralia 2010): • Mitigation—reduce Australia’s greenhouse gas emissions • Adaptation—adapt to the climate change that cannot be avoided • Global solution—help shape a collective international response In its climate change white paper, the national government states that several principles will guide its efforts: • Decisions that it makes today will affect its future vulner- ability. • Uncertainty is a reason for flexibility and creativity, not for delay. • Businesses and the community must play their part. • Governments have an important capacity-building and reform role. • The roles of commonwealth, state, territory and local gov- ernments are different. With respect to infrastructure, “significant current invest- ments in infrastructure and its long lifespan make it essential to consider the impacts of climate change now to avoid lock- ing in ineffective and inappropriate infrastructure and poli- cies. The commonwealth has a key interest in ensuring the owners of nationally significant infrastructure (such as ports, roads, and infrastructure for water, electricity, and telecom- munication services) provide continued and uninterrupted functioning of these assets, which are critical to supporting our national economy” (Commonwealth of Australia 2010). Canada In Canada, climate change does not appear to be the juris- diction of a single agency. Climate change activities can be found on Environment Canada and Natural Resources Can- ada’s websites, and the government of Canada also has a web- site devoted to climate change. On its website, it describes the following four investments it has made to help Canadians adapt to climate change and its impacts: • Developing a pilot alert and response system to protect the health of Canadians from infectious disease • Assessing key vulnerabilities and health impacts related to climate change in Northern/Inuit populations • Improving predictions of climate changes in Canada • Disseminating management tools for adaptation and sup- porting the development and implementation of regional adaptation programs In addition, Natural Resources Canada through its Climate Change Impacts and Adaptation Division has funded more than 300 impacts and adaptation research projects, which have emphasized local decision-maker participation in addressing climate change impacts and adaptation. United Kingdom The Climate Change Act of 2008 made the United King- dom the first country in the world to have a legally binding, long-term framework to cut carbon emissions. The act also created a framework for building the United Kingdom’s abil- ity to adapt to climate change. The Climate Change Act cre- ated a new approach to managing and responding to climate change in the United Kingdom by: • Setting ambitious, legally binding targets; • Taking powers to help meet those targets; • Strengthening the institutional framework; • Enhancing the United Kingdom’s ability to adapt to the impact of climate change; and • Establishing clear and regular accountability to the UK Parliament and to the devolved legislatures.

142 Key provisions of the act specific to adaptation are: • A requirement for the government to report at least every 5 years on the risks to the United Kingdom of climate change and to publish a program setting out how these will be addressed; • The introduction of powers for the government to require public bodies and statutory undertakers to carry out their own risk assessment and make plans to address those risks; and • An Adaptation Subcommittee of the Committee on Cli- mate Change, providing advice to, and scrutiny of, the gov- ernment’s adaptation work. The United Kingdom has produced the Climate Change Risk Assessment (CCRA), which is the first-ever compre- hensive assessment of potential risks and opportunities for the United Kingdom from climate change (Department for Environment, Food and Rural Affairs 2012). This represents a key part of the government’s response to the Climate Change Act of 2008, which requires a series of assessments of climate risks to the United Kingdom. The CCRA includes a detailed analysis of over 100 climate impacts, on the basis of their likelihood, the scale of their potential consequences, and the urgency with which action may be needed to address them. The CCRA classifies risks and opportunities into three broad impact classes—“low,” “medium,” and “high”—and also iden- tifies those risks that are highly uncertain and difficult to quan- tify. In addition, projected ranges of possible climate outcomes are given across the three emission scenarios for each of the three future time periods. Potential climate impacts are discussed within these three timeframes: “the 2020s” (2010–2039), “the 2050s” (2040–2069), and “the 2080s” (2070–2099). The CCRA methodology has been developed through a number of stages involving expert peer review. The approach developed is a man- ageable, repeatable methodology between the 5-year cycles of the CCRA. Confidence in a large number of the CCRA findings is gen- erally low to medium, with only risks that are already being experienced and those related to increased temperatures clas- sified as high. Several of the emerging risks examined are potentially very significant, but “current level of knowledge” means that there are also large uncertainties, especially with respect to potential climate impacts on ecosystems and busi- ness networks. With regard to transportation impacts, increased winter rainfall and higher river flows may lead to more damage to road and rail bridges. Old masonry arch bridges are most at risk from “scouring,” where their foundations can be washed away. Bridges can also be weakened during floods by the impact from floating debris (e.g., motor vehicles) and the washing-out of loose masonry and “fill” material resulting from poor bridge maintenance. The Climate Change Act of 2008 places a requirement on the secretary of state to lay a program of actions before Par- liament addressing the risks identified in the CCRA “as soon as reasonably practicable” after the CCRA. This program will be the first National Adaptation Program (NAP) covering a period of 5 years (2013–2018). The NAP will be reviewed and a new program developed on a 5-year cycle, following each new CCRA. The first NAP will focus on helping UK busi- nesses, local authorities, and society to become more resilient or “climate ready” to climate change impacts. 3.3.2 International Adaptation Initiatives for the Transportation System Australia The Australian government’s Climate Change Impacts & Risk Management: A Guide for Business and Government pro- poses a process for organizations to investigate the risks of climate change (Commonwealth of Australia 2006). It asks users of the guide to “identify those activities and assets that are at risk from a changing climate.” The workshop-based process has participants “(1) consider (based on their profes- sional knowledge) which activities and assets of the organiza- tion are sensitive to climate change and (2) form a judgment as to whether climate change is a significant source of risk to the assets and activities relative to other sources of risk” (p. 18). The first step in the workshop-based process begins before the workshop. It calls for all participants in the climate change risk management exercise to understand the context in which the evaluation will be occurring. Establishing the context consists of five parts: • Defining how the climate will be assumed to change in the future • Defining the scope of the assessment including activities to be covered, geographic boundaries, and the time horizon • Determining whose views need to be taken into account, who can contribute to the analysis, and who needs to know its outcomes • Defining how risks will be evaluated by clarifying the objec- tives and success criteria for the organization and establish- ing scales for measuring consequences, likelihoods, and risk priorities • Creating a framework that will assist in identifying risks by breaking down the organization’s concerns into a number of areas of focus and relating them to the climate scenarios The guide recognizes that for some issues there may be need for more detailed analysis (for reasons of needing to better

143 understand the climate change itself, needing to better under- stand the impact of climate change on operations, or to better understand and evaluate the treatment options). The guide provides a brief overview of the above issues, but because the issues affecting individual organizations will be different it did not go into great detail. The guide concludes with informa- tion about how to prepare and plan for a climate change risk management workshop. England Perhaps the most fully developed adaptation framework is that described in the Highway Agency’s Climate Change Adap- tation Strategy (Highways Agency and Parsons-Brinckerhoff 2008). The Highways Agency Adaptation Strategy Model (HAASM), which is the focus of Volume 1 of Climate Change Adaptation Strategy, is a seven-step process for developing a climate change program. It provides a method for prioritiz- ing risk and identifies staff members responsible for different climate change adaptation program development efforts. The other international reports reviewed do not provide such an inclusive look at climate change adaptation. Figure II.7 pro- vides a graphic overview of the HAASM. The HAASM model is one of the best examples of incorpo- rating risk into its analysis. The following paragraphs explain the seven-stage process. Stage 1: Define Objectives and Decision-Making Criteria. The first step of the HAASM is to define the objectives and decision-making criteria so that the model is aligned with the agency’s mission. The objective was “to enable the High- ways Agency to systematically develop and implement its responses to the challenges of climate change in support of the delivery of its corporate objectives” (Highways Agency and Parsons-Brinckerhoff 2008, p. 5). The decision-making criteria for selecting adaptation actions are in “accord with the Highways Agency’s sustainability requirements and pro- vide the optimum balance between minimum whole life- cost, certainty of risk, and residual risk” (p. 5). Stage 2: Identify Climate Trends that Affect the Highways Agency. The second stage categorizes possible climate changes hazards into primary and secondary impacts based on their impacts on the Highways Agency’s activities. The possible climate changes form the basis for identifying vul- nerabilities in Stage 3. Source: Highways Agency and Parsons-Brinkerhoff (2008). Figure II.7. Highways Agency Adaptation Strategy Model.

144 Stage 3: Identify Highways Agency Vulnerabilities. Vul- nerabilities are the Highways Agency activities that could be affected—positively or negatively—by climate change. They represent the ways the Agency may need to change its current practices in the future. The vulnerabilities are documented in a vulnerability schedule, which considers how climate change impacts could affect the delivery of the Highways Agency’s corporate objectives. Stage 4: Risk Appraisal. Stage 4 considers the climate change–associated risks as they relate to the vulnerabilities so that the Highways Agency can focus its climate change adap- tation efforts to those activities that are most at risk. Four primary criteria are used in the risk appraisal: uncertainty, rate of climate change, extent of disruption, and severity of disruption. The Highways Agency employs a methodical way of scoring vulnerabilities. Each vulnerability receives a high, medium, or low ranking for each of the primary risk appraisal criteria and the rankings are converted to numbers (3, 2, 1, respectively). Rather than create a single, composite score, the HAASM develops five scores reflecting different reasons for taking action. Stage 5: Options Analysis to Address Vulnerabilities. Stage 5 establishes a preferred option for managing the risk associated with each of the vulnerabilities identified in Stage 3 and prioritized in Stage 4. In some cases, the preferred option will be apparent while others may require more detailed anal- ysis. To determine the best option, the HAASM recommends that feasible options are considered, expected outcomes are determined, and costs and benefits are estimated. “The key requirement is for experts to consider carefully the sustainable options they consider have the potential to offer the minimum whole-life-cost, minimum risk, and greatest certainty of out- come” (Highways Agency and Parsons-Brinckerhoff 2008). Stage 6: Develop and Implement Adaptation Action Plans. In Stage 6, detailed adaptation plans for each preferred option are developed. “Wherever possible, the adaptation action plans will define the steps necessary to modify existing Highways Agency Standards, Specifications, and other operating proce- dures, rather than lead to the development of new require- ments. In some cases, they may determine that no immediate action is necessary, but instead a trigger for future review [is needed]” (Highways Agency and Parsons-Brinckerhoff 2008). Stage 7: Adaptation Program Review. Stage 7 draws key information from the adaptation action plans into an overall adaptation program. A climate change program manager is responsible for implementation and oversight of the program and preparing an annual Climate Change Adaptation Progress Report. As part of Stage 7, it is expected that four feedback loops are completed. The model recommends that the process stages be revisited and information revised as needed based on the findings. Scotland and Canada Two other international reports of interest included the Scottish Road Network Landslide Study: Implementation and The Road Well Traveled: Implications of Climate Change for Pavement Infrastructure in Southern Canada. These fol- lowed a more technical approach for evaluating impacts. The studies were less concerned with setting up organizational protocols of risk management and more interested in testing climate change impacts on the landscape and infrastructure. The Scottish Road Network Landslide Study: Implemen- tation report focused on assessing and ranking the hazards presented by debris flow (Winter et al. 2008). The hazard assessment process involved “the GIS-based spatial determi- nation of zones of susceptibility which are then related to the trunk road network by means of plausible flow paths to deter- mine specific hazard locations. The approach taken, using a GIS-based assessment, enabled large volumes of data to be analyzed relatively quickly and was able to rapidly deliver a scientifically sound platform for the assessment. This desk- based approach to hazard assessment was then supplemented by site-specific inspections, including site walkovers, to give a hazard score for each site of interest. The subsequent hazard ranking process involved the development of exposure scores predicated primarily upon the risk to life and limb, but also taking some account of the socioeconomic impact of debris flow events. Finally, these scores were combined with the haz- ard scores to give site-specific scores for hazard ranking from which a listing of high hazard ranking sites in Scotland was produced” (Winter et al. 2008, p. 6). The Road Well Traveled: Implications of Climate Change for Pavement Infrastructure in Southern Canada used two different methodologies to test the impact of different climate change– related variables on pavement performance (Mills et al. 2007). The first set of case studies “examined deterioration-relevant climate indicators that are routinely applied or referenced in the management of pavement infrastructure” (Mills et al. 2007, p. vii). The second set of case studies used the AASHTO Mechanistic–Empirical Pavement Design Guide. A series of analyses were conducted to test the (1) influence of climate and climate change alone, (2) influence of structure type and baseline traffic volume, and (3) combined influence of traffic growth and climate change. The study does not raise signifi- cant concern over the impacts of climate change on pavement performance. However, it did foresee that secondary and ter- tiary roads (with weak pavement structures and excessive traffic loads) will experience more impacts associated with climate change (p. 68).

145 3.4 Diagnostic Framework A diagnostic framework provides highway agency staff with a general step-by-step approach for assessing climate change impacts and deciding on a course of action. A framework can be applied from the systems planning level down to the scale of individual projects. The framework described in this sec- tion was tested in three states and modified based on feed- back from state DOT officials. A more detailed description of the diagnostic framework is found in Part I, the Practitioner’s Guide, that was developed as part of this research. This section will present only a summary of the key steps in the framework. The diagnostic framework is shown in Figure II.8. The fol- lowing paragraphs summarize the key steps in this framework. Step 1: Identify Key Goals and Performance Measures The diagnostic framework begins with identifying what is really important to the agency or jurisdiction concerning potential disruption to the transportation system or facilities. At a high level, this includes goals and objectives. At a systems management level, this includes performance measures. Thus, for example, goals and performance measures could reflect economic impacts, disruptions of passenger and freight flows, harmful environmental impacts, etc. In the context of adap- tation, an agency might be mostly concerned with protecting those assets that handle the most critical flows of passengers and goods through its jurisdiction, such as interstate highways, air- ports, or port terminals. Or, in the context of extreme weather events, it might focus on roads that serve as major evacuation routes and/or roads that will likely serve as routes serving recov- ery efforts. Or, focus might be given to routes and services that will provide access to emergency management and medical facilities. It is important that these measures be identified early in the process because they influence the type of information produced and data collected as part of the adaptation process. They feed directly into the next phase, defining policies that will focus agency attention on identified transportation assets. Step 2: Define Policies on Assets, Asset Types, or Locations that Will Receive Adaptation Consideration Changes in climate can affect many different components of a transportation system. Depending on the type of hazard or Figure II.8. Adaptation Assessment Diagnostic Framework

146 threat, the impact to the integrity and resiliency of the system will vary. Given limited resources and thus a constrained capac- ity to modify an entire network, some agencies might choose to establish policies that limit their analysis to only those assets that are critical to network performance or are important in achieving other objectives (e.g., protecting strategic economic resources, such as major employment centers, industrial areas, etc.). Or, because of historical experience with weather-related disruptions, the agency might choose to focus its attentions on critical locations where weather-related disruptions are expected. These objectives follow directly from Step 1. If an agency wants to conduct a systematic process for identifying the most critical assets, the criteria for identifying the assets, asset types, or important locations might include (1) high-volume flows, (2) linkage to important centers such as military bases or intermodal terminals, (3) serving highly vulnerable populations, (4) functioning as emergency response or evacuation routes, (5) condition (e.g., older assets might be more vulnerable than newer ones), and (6) having an impor- tant role in the connectivity of the national or state transporta- tion network. However, agencies may not want to look at only critical assets because of the potential to miss “big issues” that were unforeseen elsewhere on the network and the political difficulty in saying some areas will be considered and others will not. This was one of the conclusions of the FHWA pilot case studies mentioned earlier. Step 3: Identify Climate Changes and Effects on Local Environmental Conditions Step 3 identifies over the long term those changes in climate and the corresponding changes in local environmental condi- tions that could affect transportation design and operation. To identify climate changes and the effects on local environ- mental conditions, transportation officials will need to review updated regional and local climate modeling studies—or at the very least deduce local impacts from national and global climate studies. It is important to note that the current state of the practice of climate modeling varies by type of variable being forecast (e.g., increase in temperature is highly likely while there is a lot of uncertainty on regional changes in pre- cipitation) and by change in the type of local weather condi- tion (e.g., most models forecast more intense thunderstorms but there is very little consensus on whether there will be more tornados). Officials thus need to consider such information as being the best current science can produce with respect to transportation adaptation studies. The United States Geological Survey has produced a GIS- based website hosting downscaled climate data, i.e., data at more disaggregate levels, that reflect changes in average cli- matic conditions as well as in extreme values (see Chapter 3). In addition, the private vendor ClimSystems sells a software tool called SimClim™ that provides downscaled climate data for much of the U.S. and world. Step 4: Identify the Vulnerabilities of Asset(s) to Changing Environmental Conditions Step 4 matches the results of the previous two steps and assesses how vulnerable the targeted assets are likely to be to changes in local environmental and weather conditions. This assessment might entail, for example, examining potential flooding and the ability of drainage systems to handle greater flow demands or the likelihood of some segments of a facility being inundated with more frequent and severe storms. The vulnerability assessment might involve engineering analyses of the asset and the likelihood of different asset elements fail- ing due to environmental factors. Step 5: Conduct Risk Appraisal of Asset(s) Given Vulnerabilities Risk appraisal, at a minimum, considers the likelihood of the climate change occurring and causing asset failure along with some characterization of the consequences of that failure (in terms of system performance, damage costs, safety risks, etc.). England’s Highways Agency and Parsons-Brinckerhoff (2008), for example, developed a risk appraisal process based on the following four elements: • “Uncertainty—compound measure of current uncertainty in climate change predictions and the effects of climate change on the asset/activity.” • “Rate of climate change—measure of the time horizon within which any currently predicted climate changes are likely to become material, relative to the expected life/time horizon of the asset or activity.” • “Extent of disruption—measure taking account of the num- ber of locations across the network where this asset or activity occurs and/or the number of users affected if an associated climate-related event occurs. Therefore, an activ- ity could be important if it affects a high proportion of the network, or a small number of highly strategic points on the network.” • “Severity of disruption—measure of the recovery time in the event of a climate-related event (e.g., flood or landslip). This is separate from ‘how bad’ the actual event is when it occurs, e.g., how many running lanes [are lost]; it focuses on how easy/difficult it is to recover from the event, i.e., how long it takes to get those running lanes back into use.” The uncertainty and rate of climate change considerations provide a qualitative characterization of likelihood whereas the extent and severity of disruption elements characterize consequence.

147 Step 6: Identify Adaptation Options for High-Risk Assets and Assess Feasibility, Cost Effectiveness, and Defensibility of Options Identifying and assessing appropriate strategies for the challenges facing critical infrastructure assets is a core com- ponent of the process shown in Figure 8. Such strategies might include modifying operations and maintenance prac- tices (such as developing and signing detour routes around areas at a heightened risk of road closure), designing extra redundancy into a project, providing above-normal reserve capacity, incorporating a greater sensitivity to the protec- tion of critical elements of the project design (such as bet- ter protection against bridge scour or high winds), designing with different design standards that reflect changing condi- tions (such as higher bridge clearances for storm surges), or planning for more frequent disruptions. In particular with respect to design standards, a more robust approach could be adopted that takes into account risk and uncertainty. In many ways, considering climate-induced changes in the design process follows a model that has been applied in earth- quake engineering. Building codes and design standards have been changed to reflect the forces that will be applied to a structure during a seismic event. Substantial research on the response of materials, soils, and structures themselves has led to a better understanding of the factors that can be incorpo- rated into engineering design to account for such extreme events. Similarly, other design contexts reflect forces that might be applied during collisions, fires, or heavy snows. The logical approach for considering the best design for climate- induced changes is to examine the relationship among the many different design contexts that a structure might be fac- ing and determine which one “controls” the ultimate design. Step 7: Coordinate Agency Functions for Adaptation Program Implementation (and optionally identify agency/public risk tolerance and set trigger thresholds) This step in the diagnostic framework identifies which agency functions will be affected the most by changes in infrastructure management practices. Given the range of cli- mate stressors and extreme weather events that states might face, it is likely that many of an agency’s functional units— planning, project development, operations, construction, and maintenance—will have some role to play in developing a strategy. Furthermore, it is reasonable to expect that the new challenges imposed upon transportation infrastructure man- agers by climate change will require new adaptive efforts that are dependent upon interagency cooperation. For example, an analysis of the impact of riverine flooding on transporta- tion and other infrastructures may determine that the most cost-effective adaptation will involve a combination of bridge design adjustments and river channel widening, thus neces- sitating coordination between the transportation agency and the USACE. Planning for failures (e.g., prepositioning replace- ment materials in highly vulnerable locations) is important too and may be needed more with increasing frequency and intensity of extreme weather events. Many of the changes in climate considered as part of this assessment will likely not occur for decades, and it is also likely that the full extent of the estimated impacts of such changes on transportation facilities or systems may not occur until even further into the future. An agency might want to establish “trigger” thresholds that serve as an early warning system so that agency officials can examine alternative ways of designing, constructing, operating, and maintaining trans- portation infrastructure in response to higher likelihoods of changed environmental conditions. The adaptive systems management approach is foremost an iterative process. Realization of the intended benefits of this approach (minimization of risk and development of cost-effective adaptation strategies) requires that the latest information on changing environmental conditions and system performance priorities be incorporated into the process through monitoring external conditions and asset performance/condition, either in an asset management sys- tem or through some other means. Step 8: Conduct Site Analysis or Modify Design Standards, Operating Strategies, Maintenance Strategies, Construction Practices, etc. When a decision is made to take action, the agency should implement whatever cost-effective strategies seem most appro- priate. As shown in Figure II.8, this could range from changes in design procedures to changes in construction practices. If the focus of the adaptation assessment is on specific assets in a particular location, more detailed engineering site analyses might be needed. Once such actions are implemented, the adaptation assess- ment process links back to identifying vulnerabilities. Given that the agency has now changed the status or condition of a particular asset, at some point in the future it might be neces- sary to determine yet again what future vulnerabilities might occur given this new condition. As noted earlier, Part I, Practitioner’s Guide, provides a far greater level of detail on the application of this diagnostic framework in different contexts.

148 4.1 Introduction The impact that climate change could have on the future transportation system depends on both the changes to society and the transportation system that supports it, and the mag- nitude and nature of the climate changes that will take place. This chapter provides an overview of potential demographic, land use, and transportation system changes in coming years, and projections for key climate change drivers based on up-to- date climate modeling. 4.2 Potential Demographic, Land Use, and Transportation System Changes in the United States by 2050 Because climate change occurs over decades, developing sound adaptation strategies requires a long-term perspective. Transportation officials need to consider not only the existing highway infrastructure—which in many cases will be in service for 50 or more years—but also how transportation networks may change over time and how climate impacts and adap- tation may need to be integrated into future changes to the highway system. Shifts in demographic trends, land use pat- terns, and advances in transportation technology over the next few decades will have profound impacts on how the highway system functions, its design, and its spatial extent. As trans- portation officials shape the future highway system to address new demands, a consideration of future climate conditions should be considered as part of the planning and decision- making process. The following summary provides an over- view of broad national trends in demographics, land use, and transportation systems that have the potential to influence how the future highway system could be used, thus reflecting the impacts that climate change could have on transportation systems and on the economic and social benefits associated with system use. 4.2.1 Population and Demographics The United States will continue to grow. By mid-century, population is projected to reach just under 400 million people (Bureau of the Census 2012). This growth in U.S. population is projected to be concentrated in specific areas of the country. Between now and 2050, most population growth is expected to occur in the southern and western regions of the United States. Growth rates are anticipated to be particularly high in coastal counties across the country, especially in the Southeast. This growth pattern is particularly important for adaptation planning, as increasing coastal populations provide higher population exposure to serious effects of changing climate conditions, including rising sea levels and, on the East and Gulf Coasts, more intense hurricanes. If this development and population growth pattern continues, special attention will need to be devoted to ensuring housing and infrastructure investments in these locations are resilient to these impacts. Also, precipitation in the southwestern United States, one of the nation’s projected growth areas, is likely to decrease in future decades as the result of climate change, thus creating significant challenges with providing the water that is necessary to support urban populations (Christensen et al. 2007). In addition to the expected growth in the Southeast and West, some researchers have noted another spatial trend that could become more pronounced in the future—the forma- tion of megaregions. Megaregions are defined as large inter- connected networks of metropolitan centers (often consisting of many states) linked by transportation infrastructure. Considering urbanization on this scale captures the political, economic, and spatial levels at which some believe planning should address the challenges of agglomerations of economic activity and population (Ross 2009). According to Carbonell and Yaro (2005), more than one-half of the future popula- tion and about two-thirds of the economic growth will occur within eight megaregion areas through 2050. The Gulf Coast and Florida/Peninsula megaregions, two of the eight, have C H A P T E R 4 Context for Adaptation Assessment

149 particularly high vulnerabilities to projected sea-level rises and potential changes to hurricane intensity and frequency. Similar to other western nations, the U.S. population is aging. The Census Bureau projects that U.S. population in 2050 will consist of over 88 million people aged 65 years or older, comprising about 20 percent of the future population (Bernstein and Edwards 2008). This group will include the 19 million people in the “baby boomer” generation, who will be 85 years of age or older. The elderly, in particular the impoverished elderly, are an especially vulnerable group to projected climate change impacts such as longer and hotter heat waves and more intense storms. 4.2.2 Land Use The demographic factors described above—including the large wave of baby boomers set to retire, increased immigration, new land use policies, and shifting market demand—will influence the types and locations of developments. Housing development could experience a dramatic surge by mid- century. According to a TRB study, most of the housing for the nation’s future population growth and replacement housing has yet to be built (Committee for the Study on Relationships among Development Patterns, Vehicle Miles Traveled, and Energy Consumption 2009). In fact, up to 105 million additional housing units may need to be built by 2050 to meet demand—nearly doubling the 2000 housing stock. The increase in housing units assumes new or replace- ment housing due to the difficulty of converting the existing housing stock to higher-density units. Some professionals in the transportation planning and real estate industries believe that the future will bring a shift toward more compact development in urbanized areas (Cowden 2009). Evidence seems to suggest that there is currently an imbalance between the demand for compact housing and its supply. According to the report, 35 percent of potential residents want walkable communities, while only 2 percent of existing communities meet these characteristics. On the other hand, there is still some skepticism that land use patterns will change dramatically. Some believe low- density “sprawl” development patterns will likely continue to be common practice once market conditions improve. For example, the TRB report mentioned earlier, written by an expert committee assembled to investigate the impacts of compact development on driving, noted disagreement among committee members on the scale to which compact devel- opment could occur by 2050. Committee members skeptical of a large-scale shift toward compact development cited the inertia of existing housing trends, entrenched low-density land use policies, and established housing preferences as reasons for their pessimism (Committee for the Study on Relationships among Development Patterns, Vehicle Miles Traveled, and Energy Consumption 2009). Although future development patterns are difficult to predict, the literature suggests that there will be a very large demand for new development over the next 50 years, and where this development locates and what form it takes will have an influence on the location and types of transportation capacity improvements that will be necessary. 4.2.3 Potential Changes to Transportation Systems and Technology Similar to the difficulty in predicting future land use patterns, expectations of what the future highway system will look like vary widely, often depending on the level of investment that is assumed in the system. Many large-scale rehabilitation or reconstruction efforts likely will take place over the next half-century. AASHTO notes that many existing roadways are too old to be subjected to the same re-surfacing practices that have been in place since their construction and that total reconstruction will likely be necessary (AASHTO 2010). Additionally AASHTO states that one of the more important future highway system needs will be the likely rehabilitation or replacement of many of the Interstate system’s 55,000 bridges and 15,000 interchanges, pending findings from a recommended needs assessment of the Interstate system. Technologies related to “smart” sensors, more durable materials, and low-weight, high-strength composites could also be in widespread use in the 2030 to 2050 timeframe. If such efforts are made, it would represent a remarkable opportunity to incorporate climate change adaptation mea- sures into the upgrade of the nation’s major highway system. Given what was described earlier as being the areas of growth in population in the United States in the next several decades, it seems likely that much of the pressure for network expansion will be in these same areas. As was also noted, these areas are also likely to be prone to some of the most dramatic changes in climate facing the United States. Thus, there will likely be some real opportunities to consider seriously where this new infrastructure will be placed and how it will be built. With respect to system operations, both government and private companies have been working to improve the delivery of real-time traffic information (e.g., Google Maps, Traffic.com) to drivers so that they are able to make better informed deci- sions and avoid congestion. Many municipalities already have started improving the delivery of traffic information through electronic signs erected over roadways, roadway information phone lines, or local radio stations. The increasing provision of up-to-date road condition information will be helpful as severe weather events—expected to increase in response to climate change—may render some links in the road network impassable necessitating quick plotting of alternate routes. This was exactly what happened in Vermont in response to Topical Storm Irene.

150 In summary, five major “contextual” messages have been identified in this research that relate to how socioeconomic and transportation system characteristics could affect the magnitude and direction of climate change impacts on the transportation system: • Message 1: The U.S. population will continue to grow, with most of this growth occurring in urban areas and in parts of the country expecting notable changes in climate. • Message 2: The composition of this population will be very different than it is today, with more diverse populations and elderly in the nation’s population mix. • Message 3: Significant levels of housing and corresponding development will be necessary to provide places to live and work for this population, with much of this development likely to occur in areas subject to changing environmental conditions. • Message 4: Increasing population growth will create new demands for transportation infrastructure and services, once again in areas that are vulnerable to changing climate conditions. • Message 5: The nation’s highway system will be facing increasing demands for reconstruction and rehabilitation over the next 40 years (to 2050), which provides an oppor- tunity to incorporate climate adaptation strategies into such efforts, if appropriate. 4.3 Expected Changes in Climate Climate change projections are a product of assumptions about future greenhouse gas (GHG) emissions and how the atmosphere and climate responds to those emissions. This research analyzed a wide range of possible changes in climate, including two high-GHG-emissions scenarios, a middle-emissions scenario, and a low-emissions scenario. The emissions scenarios, shown in Table II.2, were developed by the IPCC in Emissions Scenarios [also known as the Special Report on Emissions Scenarios (SRES); Nakicenovic et al. 2000]. The two highest-emissions scenarios, A1FI and A2, were used for a “high-emissions scenario” and B1 was used as a “low-emissions scenario” in this research. The best available information on how global climate will change in the future comes from general circulation models (GCMs), which divide the world into grid cells that are typically one hundred to a few hundred miles across. These models provide some insight into potential changes in climate at this scale. But with such large grids, important climate processes such as thunderstorms and the local effects of mountains and coastlines are unresolved or modeled via simplified processes. In general, the GCMs simulate large geographic areas and timescales better than smaller geographic areas and time- scales. Also, the models tend to simulate temperature better than precipitation, although precipitation is better modeled over large geographic areas than small areas. The models also simulate annual changes better than seasonal changes, and seasonal changes better than monthly changes. (Those inter- ested in knowing more about climate change modeling are referred to Part I, Practitioner’s Guide.) This research divided the United States and Puerto Rico into 11 regions (see Figures II.9 and II.10). These regions were selected to capture important regional differences in climate change projections. Projected climate changes within each region are similar but distinct from changes in adjacent regions. It was also desired to make the regions consistent with those SRES Scenario Key Assumpons CO2 Concentraon in 2050 (ppm)* Projected Increase in GMT from 2010 to 2050 (°F) A1FI Very high rates of growth in global income, moderatepopulaon growth, and very high fossil fuel use 570 A2 Moderate rates of economic growth, but very highrates of populaon growth 533 A1B Same economic and populaon assumpons as the A1FI scenario, but assumes more use of low carbon eming power sources and clean technologies 533 B1 Same populaon growth as A1FI and A1B, but assumes a more service oriented economy and much more use of low carbon eming power sources and clean technologies 487 2.7 2.0 2.2 1.5 * Carbon dioxide (CO2) concentraons are currently over 390 ppm (having been approximately 280 ppm before the beginning of the Industrial Revoluon), and global temperatures rose 0.74°C (1.3°F) between 1905 and 2005 (Earth System Research Laboratory 2012; GMT = global mean temperature Source: Naki enovic et al. (2000). Solomon et al. 2007). Table II.2. Scenario characteristics from the IPCC Special Report on Emissions Scenarios.

151 Note: This figure presents change in temperature across the United States. It is based on output from MAGICC/SCENGEN, which reports data in 2.5 degree grid boxes. Each grid box is approximately 150 miles across and contains an average change in temperature and precipitation for the entire grid box. The data are interpolated and smoothed to make them more presentable. Since the data are smoothed, transitions between different changes in temperature (and precipitation) should not be taken as being exact model output. Figure II.9. Estimated increases in temperature (F) in 2050 relative to 2010 using A1FI scenario, 3C (5F) sensitivity. used by the FHWA and other federal agencies (ICF Interna- tional 2009). With two significant exceptions, the eight con- tinental regions are similar but not identical to those in the FHWA analysis, primarily because the regions need to align with the grid boxes used by the climate model applied in this research. One exception is the Great Plains region, which runs from the Canadian to the Mexican borders. The modeling for this research suggested differences in the magnitude of tem- perature increases and precipitation, as well as extreme event patterns between the northern and southern Great Plains. The region was split into the “Upper Great Plains” and “South Central” regions. Grid boxes that contained U.S. territories as well as oceans and parts of Canada or Mexico were included in coastal and border areas. Florida was the second exception. In other grid systems Florida is included in the Southeast region. However, given that climate models tend to project decreased precipitation in Florida, whereas they tend to project slightly increased pre- cipitation in the rest of the Southeast, it was determined that Florida deserved to be its own zone. Changes in annual, winter, and summer temperatures and precipitation from 2010 to 2050 were estimated for these regions as well as Alaska, Hawaii, and Puerto Rico. Average temperature and precipitation projections were developed using MAGICC/SCENGEN (M/S), which contains parameterized outputs from 20 GCMs (Wigley 2008). Typically, GCMs are expensive to run and are run only for a limited number of scenarios. M/S uses parameterized regional outputs

152 from the GCMs to estimate climate changes quickly for GHG emissions scenarios, as well as other parameters for any region of the world. It is generally considered better to use multiple GCM outputs rather than a single model because the range of results across an array of models gives a better indication of possible changes in climate than a single model or even an average of models (Barsugli et al. 2009). This analysis used 10 of the 20 climate models that best simulate the current U.S. climate using the A1FI emissions scenario (Wigley 2008). These models gave a range of projected climate changes, particularly at the regional scale. A more detailed description of the M/S model used in this research is found in Appendix A. Figures II.9 and II.10 show the projected changes in average temperature and average precipitation across the 10 GCMs for all of the regions. Appendix B presents the results of the analysis using so-called whisker diagrams. The composite figures give an indication of how projections can vary within and across regions, while the box-and-whisker diagrams show how projections in each region can vary across models. Both types of information are useful. For example, Fig- ure II.10 on summer precipitation changes shows some areas in Region 2 (Upper Great Plains) having a slight increase in precipitation and some having a slight decrease. In contrast, the box-and-whisker diagram for Region 2 (Figure II.11) shows that median annual precipitation change is close to zero and the Note: This figure presents change in precipitation across the United States. It is based on output from MAGICC/SCENGEN, which reports data in 2.5 degree grid boxes. Each grid box is approximately 150 miles across and contains an average change in temperature and precipitation for the entire grid box. The data are interpolated and smoothed to make them more presentable. Since the data are smoothed, transitions between different changes in precipitation (and temperature) should not be taken as being exact model output. Figure II.10. Estimated percentage change in summer precipitation in 2050 relative to 2010 using A1FI scenario, 3C (5F) sensitivity.

153 box (which captures the 25th and 75th percentiles) is almost equally above and below zero. The whiskers have a much wider range. In total, Figure II.10 suggests that on average, northern areas in Region 2 are more likely to have relatively more precip- itation than southern parts of the region. The box-and-whisker diagram, however, indicates that it is uncertain as to whether total precipitation across the region will increase or decrease. Scenarios of climate change should consider increases and decreases in precipitation. In general, the amount of relative increase in precipitation could be slightly higher in northern areas than in southern parts of the region. 4.3.1 Average Temperature Projections This section first presents projections of annual tempera- ture change followed by projections of winter and summer temperature change by 2050. Annual Temperatures Increased GHG emissions are projected to result in increased temperatures across the United States. Assuming emissions follow the A1FI emissions scenario with a climate sensitivity of 3.0°C, temperatures in the lower 48 states are projected to increase about 4°F (2.3°C) by 2050 relative to 2010. [It is interesting to note that in the last 50 years, average U.S. tem- peratures, including Alaska, increased 2°F (Karl et al. 2009).] While all U.S. regions are projected to increase significantly in temperature, the amounts will vary by location and season. In general, areas farther inland will be warmer than coastal areas, because the relatively cooler oceans will moderate the warming over coastal lands. In addition, northern areas will warm more than southern areas. Snow and ice reflect sunlight and lead to cooler temperatures, whereas exposed land absorbs sunlight, which allows for a more rapid temperature increase. As the snow and ice cover decreases with higher temperatures, there will be more warming in such areas. All of the climate model projections show increased tem- peratures under all scenarios in all regions. More warming is projected for northern and interior regions in the lower 48 states than for coastal and southern regions. As can be seen in Figure II.9, the range of model projections is quite wide. Thus, while there is agreement among the models that temperatures will rise over the first half of the 21st century Figure II.11. Box-and-whisker diagram for Region 2.

154 (and beyond), there is significant uncertainty about the mag- nitude. (Note again that the projected changes in temperature would be lower with a lower GHG emissions scenario.) Winter and Summer Temperatures Seasonal changes will vary from the average annual changes, and this variation will have important consequences for the transportation system. Appendix B displays projected changes in average winter and summer temperatures for the 11 regions. The average model changes for winter in the con- tiguous 48 states are slightly lower than the average annual changes, but not in all regions. This may be because the mod- els tend to project increased precipitation in winter, which can dampen the increase in temperatures. As with annual temperatures, projected changes in seasonal temperatures are wide ranging, although the range from the 25th to 75th percentiles is much narrower. Based on this, it is reasonable to conclude that it is highly likely that winter tem- peratures will increase, but that the magnitude of warming is quite uncertain. None of the models project a decrease in summer temperatures, and thus it is not surprising that the average projected summer increases are generally higher than the average annual temperature increases. The relatively higher warming projected in summer with respect to winter may be the result of the models estimating a decrease or no change in summer precipitation in most regions (see below). Drier conditions result in more of the sun’s energy heating the atmo- sphere rather than evaporating moisture. 4.3.2 Precipitation Projections Annual Precipitation On average, global precipitation is projected to increase. As the atmosphere warms, it holds more water vapor, causing more precipitation; however, this does not mean that average precipitation will increase everywhere (more intense precipi- tation, an important design consideration, might however). Under A1FI with a 3°C climate sensitivity, the models project little change in annual precipitation by 2050 when averaged over the United States, but do show substantial precipitation changes when examined by different regions (see Appendix B). Over the last 50 years, average precipitation over the United States increased by 5 percent (Karl et al. 2009). As with temperatures, precipitation changes on average will vary by season and location (Solomon et al. 2007). Unlike the temperature projections, with one exception, the models do not show consistent projections of whether precipitation will increase or decrease by region. All but one region’s model project significant increases and decreases in precipitation; the exception being Alaska, where all of the models project an increase in annual precipitation. On average in the contiguous 48 states, the models project slightly increased precipitation in eastern regions and drier conditions in western and south central regions, the Deep South, and Florida, with the largest average precipitation increase estimated for the Northeast, and the largest decrease projected for the Southwest. In the Southwest, the entire box (see Appendix B) displaying the 25th to 75th percentiles of change in annual precipitation is below zero, showing that most models project a decrease in annual precipitation for the region. Alaska and Hawaii have even larger projected precipi- tation increases. These results conform to the IPCC estimates that average precipitation will likely increase in the Northeast and decrease in the Southwest, and that average precipitation will likely increase in Alaska and Hawaii, and decrease in the Caribbean in the summer (Christensen et al. 2007). “Likely” is defined by the IPCC as having more than a two out of three chance of being correct. In general, increasing average pre- cipitation can be expected the farther northeast one heads, but where the transition from drier to wetter will occur is uncertain. So while it appears likely that the Northeast will have more average precipitation and the Southwest less, changes in other regions in the contiguous 48 states are less certain. In contrast, Alaska and Hawaii are projected to have larger increases in annual precipitation, while Puerto Rico is projected to have a substantial decrease. The projection ranges for Hawaii and Puerto Rico are quite large relative to the average change. Winter and Summer Precipitation Generally, there is limited certainty in projected changes in summer precipitation. For most regions, the relatively low magnitude of average change compared to the wide range of projections and the disagreement among the 10 models about whether precipitation will increase or decrease suggests that the direction of change is uncertain. In general, there is a tendency for wetter winters in the northern and eastern areas and drier winters in the southern and western regions. Alaska is projected to be much wetter (all of the models except one project an increase in precipitation in Alaska). As with the projected changes in winter precipitation, it is uncertain whether summer precipitation will increase or decrease in most regions. The strongest exception is, once again, Alaska where all the models project an increase in sum- mer precipitation. In four regions—the Northwest, Upper Great Plains, Florida, and Puerto Rico—the 25th to 75th per- centiles project decreased summer precipitation. Because of the GCMs’ difficulty in simulating convective rain events (e.g., thunderstorms), the model projections for change in summer precipitation, particularly for projections for the contiguous 48 states, should not be accorded too much weight. Even with the uncertainties associated with the model pro- jections, the models tend to suggest relatively wetter winters

155 and relatively drier summers. Note that higher temperatures will increase water evaporation and consumption by vegeta- tion (transpiration). This transpiration could add to reduced summer runoff in many regions. 4.3.3 Changes in Extreme Events Typically, the quantitative climate change projections pre- sented by the IPCC estimate changes in average annual, aver- age seasonal, or average monthly temperature or precipitation. Extreme event projections, such as intense precipitation and/or temperature, are not provided. One notable exception is the number of days exceeding a temperature threshold such as 90°F (32°C) (e.g., Karl et al. 2009). For many aspects of trans- portation infrastructure design and construction, extreme weather event changes may be more important than average condition changes (Meyer et al. 2012a; 2012b). The number of frost days, temperature fluctuations, temperatures exceeding certain thresholds, and high river flow events often determine the design criteria for bridges and roads. One important exception to the lack of quantification of change in extreme events is the seminal article published by Tebaldi et al. (2006), which examined GCM estimates of changes in 10 extreme events on a regional basis. Given that Tebaldi et al. (2006) estimated changes in extremes from GCMs that were based on large grid boxes (roughly 1 degree to 4 degrees of latitude or longitude), simulating precipitation for convective events such as thunderstorms, which occur at a much smaller scale, became a significant challenge. Changes in temperature behave more uniformly but will still not capture local phenom- ena such as the influence of water bodies or mountains. The following four events are particularly important for transportation: • Intra-annual extreme temperature range, defined as the difference between the highest temperature of the year and the lowest • Total number of frost days, defined as the annual total num- ber of days with absolute minimum temperature below 32°F (0°C) • Number of days with precipitation greater than 0.4 inches (10 millimeters) • Maximum 5-day precipitation total The difference between the highest and lowest temperatures in a year suggests more extreme heat and possibly extreme cold (although it could be that the highest temperature increases more than the lowest temperature). An increase in the range is projected for most regions. The average estimated changes range from a slight decrease in Florida to a 5°F (3°C) increase in the Southeast; however, only the average changes in the Southeast and South Central regions exceed the standard devia- tion across the models. The changes are relatively small when compared to the average model estimate of the current range in 2010. All regions have minimum and maximum changes that, in absolute terms, exceed the value of the average change. Changes in frost days appear to be significant. Most of the regions are projected to have decreases of one to more than three weeks in the number of days with temperatures below freezing. The largest reductions are projected for the northern regions. Florida has virtually no days with this condition, but the climate models estimate that the state currently has fewer than 2 days below freezing a year. [Note that this does not account for year-to-year variability; the 2009–2010 winter had many freezing days in Florida (National Weather Service 2010).] It is surprising that all regions contain at least one model run with an increase in frost days. These estimates come from the low-emissions scenario B1. Even in that scenario, most models project a decrease in the number of frost days. In general, the number of frost days seems likely to be reduced. The magnitude is uncertain, but it is reasonable to assume that there will be a reduction in the number of weeks of frost days in most regions, particularly in the North. The models tend to project an increase in extreme precipi- tation, but not consistently. None of the projected changes in maximum 5-day precipitation are significant; however, the maximum precipitation is projected to rise in the Northwest, Midwest, Northeast and Southeast, although the change in the Northwest is virtually zero. The amounts are projected to decrease elsewhere. Here too, the range from maximum to min- imum is very wide, suggesting that all regions could see sub- stantial increases or decreases in 5-day maximum precipitation. Finally, the number of days with more than 0.4 inch (10 millimeters) of precipitation is projected to increase in five of the eight regions in the contiguous 48 states; however, only two of the regions have changes well above one day. Generally, the northern regions are projected to see an increase and the southern regions a decrease or no change. As with the change in maximum 5-day precipitation, none of the changes are significant and the range across models is very wide, leaving the possibility that all regions could have increases or decreases. 4.3.4 Changes in Sea Level Three components to relative sea-level rise at any given coastal location (i.e., how much sea-level rise is observed at a given location) are important for analysis. The first is average global (eustatic) sea level. The change in eustatic sea level result- ing from changes in climate often receives the most attention. The second component is the regional change in sea level. There are important regional differences in sea-level projections (indeed, current sea levels around the world are not uniform). Differences in ocean temperatures, salinity, and changes in ocean circulation result in different changes in sea level at a

156 subcontinental scale; for example, the IPCC reports that sea- level rise in the Northeast may be about 3 inches (0.1 meter) higher than in the Southeast. These differences between regions of the world could be +0.5 foot (+0.1 meter), see Meehl et al. (2007) and Bamber et al. (2009). The third component reflects whether coastal lands are ris- ing or sinking (uplift or subsidence). The weight of glaciers covering much of the Northern Hemisphere tens of thou- sands of years ago lowered the land below them. As the gla- ciers retreated, the land began to rise (uplift), particularly in northern areas. Many other coastal areas are sinking (subsid- ing) because of the damming of rivers, high levels of sedimen- tation in deltas such as in the Mississippi River Delta, and the pumping of groundwater. Also, shifts in the Earth’s tectonic plates (plate tectonics) can cause either uplift or subsidence in coastal areas. The observed rates of sea-level rise are relatively high along the Gulf Coast and mid-Atlantic, lower along the east and west coasts, and negative in the far northwest. Clearly, there are dif- ferent rates of subsidence and even uplift. Relative rates of sea-level rise below about 4 inches (0.1 meter) suggest there is uplift. That seems to be the case along most of the West Coast. With the exception of some areas in the Northeast, the East and Gulf Coasts are, in general, subsiding. During the 20th century, global sea levels rose about 0.06 to 0.08 inch (1.5 to 2 millimeters) per year, but since the early 1990s have been rising at a rate of 0.12 inch (3 millimeters) per year. Given that rates of sea-level rise can fluctuate naturally, it is not clear whether the apparent acceleration of sea level is the result of anthropogenic or natural causes (Bindoff et al. 2007). Projections of future sea-level rise vary widely. The IPCC projects that sea level will rise 8 inches to 2 feet (0.2 to 0.6 meter) by 2100 relative to 1990 (Solomon et al. 2007). This projection, however, only partially accounts for potentially significant melting of major ice sheets in Greenland and West Antarctica (Oppenheimer et al. 2007). These ice sheets contain enough water to raise sea levels 23 feet (7 meters) or more, but it would take centuries to millennia for that amount of sea-level rise to occur. The U.S. Global Change Research Program has con- cluded that sea-level rise will, however, likely exceed the IPCC projection (Climate Change Science Program 2008a). Several studies published since the IPCC report (Solomon et al. 2007) estimate that sea levels could rise 5 to 6.5 feet (1.5 to 2 meters) by 2100 (Pfeffer et al. 2008; Vermeer and Rahmstorf 2009). Pfeffer et al. (2008) conclude that the most likely increase in sea levels by 2100 is 2.6 feet (0.8 meter) relative to 1990. A recently released report by the National Research Council projects that mean sea level will rise 3 to 9 inches (8 to 23 centimeters) by 2030 relative to 2000, 7 to 19 inches (18 to 48 centimeters) by 2050, and 20 to 55 inches (50 to 140 centimeters) by 2100 (National Research Council 2012). MAGICC (Wigley 2008) was used to estimate the eustatic sea-level rise for 2050 and 2100 relative to year 2010 for each emissions scenario. As with the climate projections, combina- tions of low, medium, and high GHG-emissions scenarios, climate sensitivity, and rates of melting of ice from glaciers and major ice sheets were used. Parameters for each scenario were set as follows: • B1—sensitivity of 1.5°C, low ice melt • A1B—sensitivity of 3.0°C, medium ice melt • A1FI—sensitivity of 4.5°C, high ice melt Note that even the high ice-melt scenario does not com- pletely account for a rapid melting of the Greenland or the West Antarctic Ice Sheet should either of those events occur. The average of six GCMs used by the IPCC for sea-level rise modeling that were common with those used by MAGICC were used in the analysis. The values in the models are expressed as scalars to the eustatic rate at 0.5° × 0.5° resolution using a GIS. An average rate of sea-level rise was then calculated by state and used the spatial average of cells falling within 62 miles (100 kilometers) of the state’s shoreline to obtain the regional average scalar per state. Estimates of relative local sea-level rise accounted for sub- sidence or uplift in the coastline by examining differences in observed sea-level rates along the U.S. coasts. Tide gauge data were obtained for all long-term gauges (minimum of 30 years) from the National Oceanic and Atmospheric Administration (NOAA 2008). For the two states without tide gauges— New Hampshire and Mississippi—the state averages from Maine and Alabama were used, respectively. As the tide gauge average includes a climate and non-climate component, the climate component was removed by using the current eustatic rate of 0.7 inch (1.8 millimeters) per year from the IPCC (Solomon et al. 2007), adjusted by the regional scalar. Annual subsidence rates were assumed to continue at historic rates from 2010 to 2100. The eustatic rates were then scaled by the state-specific regional scale values and added in the total sub- sidence (or uplift) to estimate relative sea-level rise by state. State-by-state projections of sea-level rise by 2050 and 2100 relative to 2010 are presented in Tables II.3 and II.4 (note that for large states projections could very well vary along the coastal border, but these are not reflected in the tables). The B1, A1B, and A1FI columns estimate net sea-level rise by state for each of the SRES scenarios accounting for the combi- nation of sea-level rise and subsidence (or uplift). Most states are projected to have 1 foot (0.3 meter) or less of relative sea- level rise by 2050. Louisiana is projected to have at least 1 foot (0.3 meter) and up to almost 2 feet (0.61 meter) by 2050. The increase in eustatic sea-level rise reduces the apparent decrease in relative sea level in Alaska from 9 inches (0.23 meter) to less than 1 inch (0.025 meter). Projected subsidence rates for the next 40 years for most states are a few inches or less; however,

157 Table II.3. Total relative sea-level rise by 2050 (relative to 2010) in inches. Table II.4. Total relative sea-level rise by 2100 (relative to 2010) in inches.

158 Louisiana is projected to subside by about 1 foot (0.3 meter), whereas Alaska is projected to have uplift of almost 1 foot. The state projections are displayed in Figure II.12. 4.4 Summary This chapter has provided the context within which adap- tation assessment will occur. Not only does the transporta- tion official need to be concerned about the direct impacts of climate stressors on the transportation system, but ultimately changes in population, land use, and transportation systems themselves will either exacerbate or provide solutions for the much broader impacts on society. The United States in 2050 (and certainly in 2100) will be a very different country than it is today. The population will be much larger, older, more diverse, and heavily urban. Perhaps most importantly for this research, much of this population growth will occur in areas of the country projected to see potentially significant changes in climate (for example, the Southwest and Florida). In addition, it is expected that the transportation system will be much “smarter,” with the application of advanced sensors and communication technology that will provide opportunities for transportation system managers to respond to changes in climatic conditions in a more dynamic way. The need to reha- bilitate much of the U.S. transportation system over the next 40 years also provides opportunities to incorporate a climate- sensitive perspective on facility design and system operations in areas especially vulnerable to changing conditions. The next chapter discusses the types of impacts that might occur given different changes in climatic conditions. As indicated in this chapter, there is a great deal of uncertainty associated with what climate changes will occur in the future. However, given recent trends in weather conditions and based on the best science available for forecasting expected climate charac- teristics, it makes sense to consider how these future character- istics should affect the design of facilities that could last well into the latter half of this century, and how they in the shorter term might affect system operations and maintenance. Figure II.12. Projected sea-level rise, 2050 relative to 2010.

159 5.1 Introduction The study of impacts of climate change on the U.S. transpor- tation system has emerged as an important area of research in recent years (Committee for Study on Transportation Research Programs to Address Energy and Climate Change 2009). While many of these studies are overviews of the impacts to the entire transportation network, there is also a growing body of research that specifically addresses impacts on the highway system itself. Comprehensive reviews of regional, national, and international literature on this topic have been con- ducted by several groups that cover research published up to 2012. For this research project, these reviews were updated and supplemented with more recently published papers and reports. The findings from this review reveal similar types of impacts on the highway system that have been identified by various groups. As could be expected in a country the size of the United States, the potential impacts of climate changes on highways are geographically widespread and affect both infrastructure and operations. Three important literature reviews were found in the fol- lowing reports: • U.S. DOT Gulf Coast Study, Phases 1 and 2: As part of a study of potential climate impacts on the Gulf Coast transporta- tion system, this study identified the changing climate fac- tors likely to impact transportation, synthesizing findings by mode, geography, climate zone, and timeframe (Climate Change Science Program 2008b, ICF International 2012, FHWA 2012c). • TRB Special Report 290: This report focuses on the conse- quences of climate change for the infrastructure and oper- ations of the entire U.S. transportation system. The report provides an overview of the scientific consensus and high- lights flooding of coastal roads as a result of global rising sea levels, coupled with storm surges and land subsidence in some areas, as one of the most severe impacts on the road system in the United States (Committee on Climate Change and U.S. Transportation 2008). • Global Climate Change Impacts in the United States: This report presents a summary of current scientific informa- tion on climate change and on the impacts of climate change on the United States divided by sector (including transportation) and by region of the country (Karl et al. 2009). The literature consistently identifies four major categories of climate change factors and associated impacts to the high- way system; these categories are discussed in the following section. 5.2 Climate Change Impacts on the Highway Network As illustrated in Figure II.13, each of the climate factors or drivers (A) has direct implications for the condition of high- way infrastructure as well as for the operations and mainte- nance of this infrastructure (B). As the significance of these implications is assessed, transportation managers may select from a range of adaptation strategies to respond to these impacts (C). These adaptation responses will, in turn, affect the condition and resilience of the highway infrastructure, as well as the operations and maintenance requirements of the infrastructure addressed by the adaptation actions. In addition, climate drivers will have impacts on the ecological conditions in which transportation infrastructure is built and maintained; effects on the planning, design, and construction phases of the highway system; and impacts on the effective- ness of ecological mitigation measures. Through an adaptive management approach, transportation agencies can evaluate the effectiveness of adaptation strategies on system perfor- mance, and then tailor future adaptation actions to further improve performance and enhance the resilience of the high- way network. By taking pro-active measures, transportation C H A P T E R 5 Potential Impacts on the U.S. Road System

160 agencies can better protect their most vulnerable infrastruc- ture and reduce the risk of system failure, with its impact on human life and economic activity. This section reviews the range of climate impacts on infra- structure and operations/maintenance activities that may require the use of adaptation strategies. These are identified in Table II.5 and discussed in further detail in the following subsections. Infrastructure will be affected most by those climate changes that cause environmental conditions to extend beyond the range for which the system was designed (Committee on Cli- mate Change and U.S. Transportation 2008). As discussed in Section 3.3, the key climate factors and their major impacts are as follows: 1. Temperature changes, including changes in extreme maxi- mum temperature that can damage road surfaces and affect crew operations, and changes in the range of maximum and minimum temperatures that can intensify damaging freeze–thaw cycles and melt permafrost; 2. Precipitation changes, including changes in overall precipi- tation levels which can lead to more rapid infrastructure deterioration, and increased intense precipitation events which can damage roads and disrupt operations; 3. Sea-level rise that can inundate coastal roads and increase areas flooded from coastal storms; and 4. Increased intensity of hurricanes and higher storm surges, which can cause infrastructure damage and failure and create evacuation challenges. The following sections discuss the range of climate impacts on infrastructure and operations/maintenance activities. 5.2.1 Temperature Changes Change in Extreme Maximum Temperature The literature points to a likely increase in very hot days and heat waves. As discussed in Section 4.3, heat extremes and heat waves will continue to become more intense, longer lasting, and more frequent in most regions during the 21st century (Committee on Climate Change and U.S. Transpor- tation 2008). Increasing periods of extreme heat will place additional stress on infrastructure, reducing service life and increasing maintenance needs. Impacts on Highway Infrastructure. Extreme maxi- mum temperature and prolonged duration of heat waves are expected to lead to premature deterioration of infrastructure. Temperature increases have the potential to affect and reduce the life of asphalt road pavements through softening and traffic- related rutting (Karl et al. 2009, CNRA 2009, Field et al. 2007, CSIRO et al. 2007, Maine DOT 2009). Extreme heat can also stress the steel in bridges through thermal expansion and movement of bridge joints and paved surfaces (Karl et al. 2009, CSIRO et al. 2007, New York City Panel on Climate Change 2010). Impacts on Operations/Maintenance. The increase in very hot days and extended heat waves are expected to Figure II.13. Climate drivers that impact highway infrastructure and operations, resulting in need for adaptation strategies.

Table II.5. Summary of climate change impacts on the highway system. Climac/ Weather Change Impact to Infrastructure Impact to Operaons/Maintenance Temperature Change in extreme maximum temperature Premature deterioraon of infrastructure. Damage to roads from buckling and rung. Bridges subject to extra stresses through thermal expansion and increased movement. Safety concerns for highway workers liming construcon acvies. Thermal expansion of bridge joints, adversely affecng bridge operaons and increasing maintenance costs. Vehicle overheang and increased risk of re blowouts. Rising transportaon costs (increase need for refrigeraon). Materials and load restricons can limit transportaon operaons. Closure of roads because of increased wildfires. Change in range of maximum and minimum temperature Shorter snow and ice season. Reduced frost heave and road damage. Later freeze and earlier thaw of structures because of shorter freeze season lengths. Increased freeze–thaw condions in selected locaons creang frost heaves and potholes on road and bridge surfaces. Increased slope instability, landslides, and shoreline erosion from permafrost thawing leads to damaging roads and bridges due to foundaon selement (bridges and large culverts are parcularly sensive to movement caused by thawing permafrost). Hoer summers in Alaska lead to increased glacial melng and longer periods of high stream flows, causing both increased sediment in rivers and scouring of bridge supporng piers and abutments. Decrease in frozen precipitaon would improve mobility and safety of travel through reduced winter hazards, reduce snow and ice removal costs, decrease need for winter road maintenance, and result in less polluon from road salt, and decrease corrosion of infrastructure and vehicles. Longer road construcon season in colder locaons. Vehicle load restricons in place on roads to minimize structural damage due to subsidence and the loss of bearing capacity during spring thaw period (restricons likely to expand in areas with shorter winters but longer thaw seasons). Roadways built on permafrost likely to be damaged due to lateral spreading and selement of road embankments. Shorter season for ice roads. Precipitaon Greater changes in precipitaon levels If more precipitaon falls as rain rather than snow in winter and spring, there will be an increased risk of landslides, slope failures, and floods from the runoff, causing road washouts and closures as well as the need for road repair and reconstrucon. Increasing precipitaon could lead to soil moisture levels becoming too high (structural integrity of roads, bridges, and tunnels could be compromised leading to accelerated deterioraon). Less rain available to dilute surface salt may cause steel reinforcing in concrete structures to corrode. Road embankments could be at risk of subsidence/heave. Subsurface soils may shrink because of drought. Regions with more precipitaon could see increased weather related accidents, delays, and traffic disrupons (loss of life and property, increased safety risks, increased risks of hazardous cargo accidents). Roadways and underground tunnels could close due to flooding and mudslides in areas deforested by wildfires. Increased wildfires during droughts could threaten roads directly or cause road closures due to fire threat or reduced visibility. Clay subsurfaces for pavement could expand or contract in prolonged precipitaon or drought, causing pavement heave or cracking. (continued on next page)

162 Climac/ Weather Change Impact to Infrastructure Impact to Operaons/Maintenance Increased intense precipitaon, other change in storm intensity (except hurricanes) Heavy winter rain with accompanying mudslides can damage roads (washouts and undercung), which could lead to permanent road closures. Heavy precipitaon and increased runoff can cause damage to tunnels, culverts, roads in or near flood zones, and coastal highways. Bridges are more prone to extreme wind events and scouring from higher stream runoff. Bridges, signs, overhead cables, and tall structures could be at risk from increased wind speeds. The number of road closures due to flooding and washouts will likely rise. Erosion will occur at road construcon project sites as heavy rain events take place more frequently. Road construcon acvies could be disrupted. Increases in weather related highway accidents, delays, and traffic disrupons are likely. Increases in landslides, closures or major disrupons of roads, emergency evacuaons, and travel delays are likely. Increased wind speeds could result in loss of visibility from dri„ing snow, loss of vehicle stability/maneuverability, lane obstrucon (debris), and treatment chemical dispersion. Lightning/electrical disturbance could disrupt transportaon electronic infrastructure and signaling, pose risk to personnel, and delay maintenance acvity. Sea Level Sea level rise Erosion of coastal road base and undermining of bridge supports due to higher sea levels and storm surges. Temporary and permanent flooding of roads and tunnels due to rising sea levels. Encroachment of saltwater leading to accelerated degradaon of tunnels (reduced life expectancy, increased maintenance costs and potenal for structural failure during extreme events). Further coastal erosion due to the loss of coastal wetlands and barrier islands removing natural protecon from wave acon. Coastal road flooding and damage resulng from sea level rise and storm surge. Increased exposure to storm surges. More frequent and severe flooding of underground tunnels and other low lying infrastructure. Hurricanes Increased hurricane intensity Increased infrastructure damage and failure (highway and bridge decks being displaced). More frequent flooding of coastal roads. More transportaon interrupons (storm debris on roads can damage infrastructure and interrupt travel and shipments of goods). More coastal evacuaons. Table II.5. (Continued).

163 affect highway operations and maintenance in several ways. The first is the probable limit on construction activities and the number of hours road crews can work due to health and safety concerns for highway workers (Karl et al. 2009; Peter- son et al. 2008). The increase in extreme heat could also lead to load restrictions on roads. Pavement damage and buckling will disrupt vehicle movements (Karl et al. 2009). Extreme heat could disrupt vehicle operations because of overheating and increased risk of tire blowouts in heavily loaded vehicles (Karl et al. 2009; Peterson et al. 2008). Higher temperatures could lead to an increased need for refrigerated freight move- ment, and thus result indirectly in higher transportation costs (Karl et al. 2009; CNRA 2009). A secondary impact of extreme and extended periods of heat, when combined with reduced precipitation, is the pro- jected increased risk of wildfires, especially in the Southwest. Fire poses a risk to infrastructure and travelers and can neces- sitate road closures (Karl et al. 2009). Change in Range of Maximum and Minimum Temperatures Changes in the projected range of temperatures, includ- ing seasonal changes in average temperatures, can also affect highway systems. The increase in range of temperatures will likely benefit highways in some ways, while increasing risks in others. Impacts on Highway Infrastructure. Warmer winters will likely lead to less snow and ice on roadways, and inci- dence of frost heave and road damage caused by snow and ice in southern locations is likely to decline. However, in some regions, warmer winters could also increase the freeze–thaw conditions that create frost heaves and potholes on road and bridge surfaces, particularly in northern locations that previ- ously experienced below-freezing temperatures throughout much of the winter. They may lead to an increase in freeze– thaw conditions in northern states, creating frost heaves and potholes on road and bridge surfaces that increase mainte- nance costs. Repairing such damage is already estimated to cost hundreds of millions of dollars annually in the United States (Peterson et al. 2008). In Alaska, warmer temperatures will likely adversely affect infrastructure for surface transportation. Permafrost thaw in Alaska will damage road infrastructure due to founda- tion settlement and is the most widespread impact (Larsen 2008). Permafrost thaw will also reduce surface load-bearing capacity and potentially trigger landslides that could block highways. Roadways built on permafrost already have been damaged as the permafrost has begun to melt and ground settlement has occurred leading to costly repairs for damaged roads. Dealing with thaw settlement problems already claims a major portion of highway maintenance dollars in Alaska (Karl et al. 2009). A study in Manitoba, Canada, projects the degradation of permafrost beneath road embankments will accelerate because of warmer air temperatures. The symp- toms of permafrost degradation on road embankments are lateral spreading and settlement of road embankments. This can create sharp dips in road surfaces which require exten- sive patching every year and lead to dangerous conditions for motorists (Alfaro 2009). In southern Canada, studies suggest that rutting and crack- ing of pavement will be exacerbated by climate change and that maintenance, rehabilitation, or reconstruction of roadways will be required earlier in the design life (Mills et al. 2007). Similarly, simulations for pavement in Alberta and Ontario show that temperature increases will have a negative impact on the pavement performance in the Canadian environment. As temperature increases, accelerated pavement deteriora- tion due to traffic loads on a warmer pavement was expected and observed. An increase in temperature would facilitate rutting because the pavement is softer. Pavement move- ment due to loads on a softer pavement would also result in increased cracking. Overall temperature changes signifi- cantly affected the level of pavement distress for the inter- national roughness index, longitudinal cracking, alligator cracking, asphalt concrete deformation, and total deformation (Smith et al. 2008). The effects of changing temperatures are particularly appar- ent in the Arctic. Warming winter temperatures, especially in the high northern latitudes of Alaska, could cause the upper layer of permafrost to thaw. Over much of Alaska, the land is generally more accessible in winter, when the ground is fro- zen and ice roads and bridges formed by frozen rivers are available (Committee on Climate Change and U.S. Transpor- tation 2008, Karl et al. 2009). Winter warming would there- fore shorten the ice road season and affect access and mobility to northern regions. Thawing permafrost could also damage highways as a result of road base instability, increased slope instability, landslides, and shoreline erosion. Permafrost melt could damage roads and bridges directly through foundation settlement (bridges and large culverts are particularly sensi- tive to movement caused by thawing permafrost) or indirectly through landslides and rockfalls. In addition, hotter summers in Alaska and other mountainous western locations may lead to increased glacial melting and longer periods of high stream flows, causing both increased sediment in rivers and scouring of bridge supporting piers and abutments. Impacts on Operations/Maintenance. The change in range of maximum and minimum temperatures will likely produce both positive and negative impacts on highway operations/maintenance. In many northern states, warmer winters will bring about reductions in snow and ice removal

164 costs, lessen adverse environmental impacts from the use of salt and chemicals on roads and bridges, extend the construc- tion season, and improve the mobility and safety of passenger and freight travel through reduced winter hazards (Karl et al. 2009). On the other hand, warmer winter temperatures could also have negative impacts on highway operations and mainte- nance. Greater vehicle load restrictions may be required to minimize damage to roadways when they begin to subside and lose bearing capacity during the spring thaw period. With the expected earlier onset of seasonal warming, the period of springtime load restrictions might be reduced in some areas, but it is likely to expand in others with shorter winters but longer thaw seasons (Peterson et al. 2008). In the far north, the season for ice roads will likely be com- pressed. Temporary ice roads and bridges are commonly used in many parts of Alaska for access to northern communities. Rising temperatures have already shortened the season dur- ing which these critical facilities can be used (Karl et al. 2009; Peterson et al. 2008; Field et al. 2007). The indirect effects of changing temperatures on travel behavior are also a consideration. For example, tourism-related traffic is projected to increase in Maine because of the longer summer season and as more people seek to escape increas- ingly hot summers in other parts of the country (Maine DOT 2009). Conversely, southern destinations (e.g., Florida, the desert Southwest) could see decreased summertime tourism. 5.2.2 Precipitation Changes Changes in Overall Precipitation As discussed in further detail in Section 4.3, changes in precipitation—of both rain and snow—will vary widely across the various regions in the United States. These changes are expected to affect highways in several ways, depending on the specific regional precipitation levels and geographic conditions. Impacts on Highway Infrastructure. In areas with increased precipitation, there is greater risk of flooding. In other areas, more precipitation may fall as rain rather than snow in winter and spring, increasing the risk of landslides, slope failures, and floods from the runoff, which can cause road washouts and closures. In addition, northern areas are projected to have wetter winters, exacerbating spring river flooding. In other areas, the increase in precipitation could lead to higher soil moisture levels affecting the structural integrity of roads, bridges, and tunnels and lead to acceler- ated deterioration. If soil moisture levels become too high, the structural integ- rity of roads, bridges, and tunnels, which in some cases are already under age-related stress and in need of repair, could be compromised. Standing water can also have adverse impacts on road base (Karl et al. 2009; Smith et al. 2008). Overall, the increased risk of landslides, slope failures, and floods from runoff will lead to greater road repair and reconstruction needs (Karl et al. 2009). Some regions of the country will experience decreased pre- cipitation. Where there is less precipitation, there may not be enough runoff to dilute surface salt causing steel reinforcing in concrete structures to corrode. In some regions, drought is expected to be an increasing problem. Impacts on Operations/Maintenance. Changes in rain, snowfall, and seasonal flooding can affect safety and main- tenance operations on roads. More precipitation increases weather-related accidents, delays, and traffic disruptions (loss of life and property, increased safety risks, increased risks of hazardous cargo accidents) (Koetse and Rietvelda 2009). In New York City and other urban areas, precipitation-related impacts may include increased street flooding and associated delays, and an increase in risk of low-elevation transportation flooding and water damage (New York City Panel on Climate Change 2010). Increases in road washouts and landslides and mudslides that damage roads are expected. Climate models tend to show wetter winters but drier sum- mers. Dry summers or droughts can lead to increased wildfires, which could threaten roads and other transportation infra- structure directly or cause road closures due to reduced vis- ibility. Areas with both wetter winters and drier summers may be particularly at risk, as wetter winters may promote increased springtime vegetation growth, in turn providing more fuel for summer wildfires. There is also increased susceptibility to mudslides in areas deforested by wildfires, particularly if wintertime precipitation increases (Karl et al. 2009). Increased Intense Precipitation Heavier rainfall downpours and more intense storms are very likely to continue to become more frequent in wide- spread areas of the United States (Committee on Climate Change and U.S. Transportation 2008). This intense pre- cipitation has immediate effects on highways and could cause changes to the ecological system that ultimately affect highway infrastructure and operations/maintenance. Impacts on Highway Infrastructure. The increase in intense precipitation could have major impacts on infrastruc- ture. In areas with heavy winter rain, mudslides and rockslides can damage roads from washouts and undercutting and lead to permanent road closures. For example, winter rain has caused yearly washouts of Highway 1 in California (Peterson et al. 2008). Heavy precipitation and increased runoff during winter

165 months are likely to increase the flood damage to tunnels, cul- verts, and coastal highways (CNRA 2009). The combination of a generally drier climate in the Southwest in the future, which will increase the chance of drought and wildfires, with more frequent extreme downpours (and occasionally wet winters) is likely to cause more mudslides and landslides that can dis- rupt major roadways (CNRA 2009). In California, the debris impacts generated by intense precipitation are well known. As these events become more intense, the state will incur even greater costs for more frequent repair (CNRA 2009). An Australian study found that in Victoria the projected increase in the frequency and intensity of extreme rainfall events has the potential to cause major flood damage to roads— especially tunnel infrastructure—due to acceleration in the degradation of materials, structures, and foundations of transport infrastructure from increased ground movement, changes in groundwater affecting the chemical structure of foundations and fatigue of structures from extreme storm events (CSIRO 2007). Bridges are more prone to extreme wind events and scouring from higher stream runoff, and bridges, signs, overhead cables, and tall structures face increased risk from greater wind speeds. Impacts on Operations/Maintenance. Generally, intense precipitation and increased runoff during winter months are likely to increase the flood damage to tunnels, culverts, and coastal highways. The number of road closures due to flood- ing and washouts will likely increase as will the potential for extreme incidents of erosion at project sites as more rain falls in heavy rain events (Maine DOT 2009). The increase in heavy precipitation will inevitably cause increases in weather-related accidents, delays, and traffic dis- ruptions in a network already challenged by increasing con- gestion. There will be potential flooding of evacuation routes and construction activities will be more frequently disrupted (Karl et al. 2009). 5.2.3 Sea-Level Rise Sea levels will continue to rise in the 21st century as a result of thermal expansion and the possible loss of mass from ice sheets (Committee on Climate Change and U.S. Transpor- tation 2008), as discussed in Section 3.3. Infrastructure in coastal areas is expected to be heavily affected by rising sea levels, often compounded by regional subsidence (the sinking of a land mass due to compaction of sediments or tectonic forces). Coastal highways are at risk from the combination of rising sea levels along with increased heightened coastal flooding potential from tropical and non-tropical storms (Oregon Coastal Management Program 2009). Storm surge risks related to hurricanes will be discussed in more detail in the next section. Impacts on Highway Infrastructure. In many coastal states, the greatest impacts and largest projected damages to highway infrastructure will come from sea-level rise (CNRA 2009). Sea-level rise will also increase the risk of coastal flood- ing and damage to transportation infrastructure; the same storm surge will now have more elevation because of higher sea levels. Sea-level rise is likely to contribute to more frequent storm-related flooding of roads in coastal floodplains. An esti- mated 60,000 miles of coastal highway are already exposed to periodic flooding from coastal storms and high waves (Karl et al. 2009). Along with the temporary and permanent flood- ing of roads and tunnels, rising sea levels and storm surges will likely cause erosion of coastal road bases and bridge supports. In addition to more frequent and severe flooding, under- ground tunnels and other low-lying infrastructure may also experience encroachment of saltwater, which can lead to accelerated degradation of infrastructure. This can reduce the structure’s life expectancy, increase maintenance costs as well as the potential for structural failure during extreme events (Peterson et al. 2008, CSIRO 2007, New York City Panel on Climate Change 2010). Underground tunnels and other low- lying infrastructure will experience more frequent and severe flooding. Higher sea levels and storm surges will also erode road base and undermine bridge supports. The loss of coastal wetlands and barrier islands will lead to further coastal ero- sion due to the loss of natural protection from wave action (Karl et al. 2009). Impacts on Operations/Maintenance. Studies from a number of coastal states indicate thousands of miles of major roadway are at risk of flooding and erosion as climate change and land subsidence combine to produce a relative sea-level rise (Climate Change Science Program 2008b; Maine DOT 2009; Heberger et al. 2009). As coastal roads are flooded more frequently and for longer periods of time, road closures may become longer and the cost of repair may rise. These affected roads may need to be protected by raising or re-routing the road (Heberger et al. 2009). The significance of the vulner- ability of coastal roads is compounded because many coastal highways serve as evacuation routes during hurricanes and other coastal storms. These routes could become seriously com- promised and lead to evacuation route delays and stranded motorists (Karl et al. 2009). 5.2.4 Increased Hurricane Intensity Hurricanes are projected to increase in intensity, with larger peak wind speeds and more intense precipitation (Committee on Climate Change and U.S. Transportation 2008, Peterson et al. 2008). The number of Category 4 and 5 hurricanes is projected to increase, while the number of less powerful hur- ricanes is projected to decrease (Bender et al. 2010; Knutson

166 2013). Three aspects of hurricanes are relevant to trans- portation: precipitation, winds, and wind-induced storm surge. Stronger hurricanes have longer periods of intense precipitation, higher wind speeds (damage increases expo- nentially with wind speed), and higher storm surge and waves. Increased intensity of strong hurricanes could lead to more evacuations, infrastructure damage and failure, and transportation interruptions in transportation service (Karl et al. 2009). The prospect of an increasing number of higher category hurricanes has serious implications for the high- way system. Impacts on Highway Infrastructure. Road infrastructure for passenger and freight services is likely to face increased flooding by strong hurricanes (Karl et al. 2009). Prolonged inundation can lead to long-term weakening of roadways. A study of pavements submerged longer than 3 days during Hurricane Katrina (some were submerged several weeks) found that asphalt concrete pavements and subgrades suf- fered a permanent strength loss equivalent to 2 inches of pave- ment (Gaspard et al. 2007). With an increase in future hurricane intensity, there will also be more damage to roadway infrastructure. Roads and bridges can be damaged during hurricanes by wave bat- tering (from water driven inland by storm surge) and high winds. Concrete bridge decks weighing many tons can liter- ally be blown off during hurricanes, as seen during Hurri- canes Katrina and Rita. The widespread damage to highways from these hurricanes illustrated the powerful effects of these intense tropical storms. Damage to signs, lighting fixtures, and supports also is a product of hurricanes force winds. Impacts on Operations/Maintenance. More intense storms will leave behind greater volumes of debris on roads, which causes road closures and disruptions until it can be cleared (Karl et al. 2009). Damage to the highway networks caused by the storms increases the challenge for system oper- ations and emergency management. In addition, there will be more frequent and potentially more extensive emergency evacuations, placing further strain on highways. At the same time, sea-level rise may render existing evacuation routes less useable in future storms. 5.3 Climate Impact to Ecological Conditions In addition to the direct effects of climate changes on high- ways, climate change will affect ecological dynamics in ways that will have implications for transportation systems. High- way infrastructure interacts with ecosystems in a number of different ways. Highway construction can destroy ecosystems by displacing natural environments, such as wetlands. Roads can act as a barrier, restricting the movement of flora and fauna and fragmenting ecosystems and changing the natural flow of water across their right-of-way. Vehicles can also be a hazard to wildlife, killing or injuring animals as they attempt to cross roads to escape rising waters or wildfires. Roads can also be a local source of pollution and damage water bod- ies, as with the materials that run off roads with rainfall, and in addition affect the level of soil saturation. Transportation professionals have worked for years with resource agencies and ecologists to understand these interactions and develop strategies to reduce or mitigate the negative effects of high- ways on ecosystems—and to identify opportunities to restore and strengthen compromised environments. Specifically with respect to climate change, changing tem- peratures, precipitation levels and extreme weather events can significantly alter the ecosystem in highly vulnerable areas. For example, the National Climate Assessment draft report (as of 2013) noted in its chapter on ecosystems that “coastal eco- systems are particularly vulnerable to climate change because many have already been dramatically altered by human stresses; climate change will result in further reduction or loss of the services that these ecosystems provide, including potentially irreversible impacts” (NCADAC 2013). The Practitioner’s Guide (Part I of this volume) discusses the impacts to ecological conditions in more detail. 5.4 Adaptation Strategies 5.4.1 Domestic Strategies Numerous adaptation strategies have been identified as a result of climate change studies. As with adaptation planning in general, at this stage, most plans identify adaptation strate- gies at a high level—a planning level, rather than an imple- mentation level. For instance, agencies might identify the need to update design standards for the new climate future but not specify which standards or what the new standards should be. Vermont In the aftermath of Tropical Storm Irene, the Vermont Agency of Transportation (VTrans) put together an climate change adaptation policy/strategy based on its experience with the storm and its aftermath. As noted in the policy, its primary goal is to “minimize long-term societal and economic costs stemming from climate change impacts on transpor- tation infrastructure” (VTrans 2012a). The policy relates to several of the VTrans’s goals: “Excellence & Innovation: Cultivate and continually pursue excellence and innovation in planning, project development, and customer service: • Ensure that there are viable alternative routes around vulner- able infrastructure such as bridges and roadways.

167 “Safety: Make safety a critical component in the development, implementation, operation and maintenance of the transporta- tion system: • Develop contingency plans for a wide variety of climate impacts to be implemented as data/information becomes available; • Utilize information technology to inform stakeholders during times of emergency; • Educate the public and other stakeholders on the threats posed by climate change and fluvial erosion hazards; • Increase inspection of infrastructure if warranted by climate change indicators; “Planning: Optimize the movement of people and goods through corridor management, environmental stewardship, bal- anced modal alternatives, and sustainable financing: • Apply a decision-making framework to incorporate cost–ben- efit analyses into adaptive plans and policy; • Increase adaptive capacity among stakeholders so that adap- tive planning can be quickly implemented upon realization of risk; “Environmental Stewardship: Build, operate, and manage transportation assets in an environmentally responsible manner: • Work to protect essential ecosystem functions that mitigate the risks associated with climate change; • Educate individuals within the agency to use best practices during recovery periods to avoid ecological damage that may further exacerbate risk; • Recognize the interconnected nature of our built environment with ecological processes. “Preservation: Protect the state’s investment in its transporta- tion system. • Policies must overcome short-term budgetary, social, and institutional constraints to avoid potentially untenable future costs” (VTrans 2012a). Some specific initiatives undertaken by VTrans included the following (VTrans 2012a): • LiDAR (light detection and ranging) mapping: VTrans, regional planning commissions, and some municipalities are undertaking LiDAR mapping efforts along primary transportation and river corridors to increase the precision of computerized flood models, update FEMA’s 100-year floodplain maps, and support the use of risk assessment tools. • State asset management: The state is collecting condition and performance data on state-owned small and large cul- verts, bridges, and pavement. VTrans is working towards development of more sophisticated deterioration models that will allow the agency to more effectively plan for long- term funding needs and to quantify performance trade- offs under different scenarios. It is expected that climate changes will require frequent updates of environmental factors in these models. • Flood resiliency training programs: Flood resiliency train- ing programs have been instituted to educate key audiences on best management practices, river dynamics and geo- morphology, and potential impacts of floods on infra- structure. Participants include VTrans personnel such as heavy equipment operators, field supervisors, and design engineers; Tri-State (Maine, Vermont, and New Hampshire) partners; contractors; and consultants. These programs will increase the adaptive capacity of VTrans and allow for responsible reactions to natural disaster events in the future. • Transportation resiliency plan: VTrans is developing methods and tools to identify roads, bridges, and other transportation infrastructure that are vulnerable to flood- ing and fluvial erosion; quantify risk as a means to prioritize needs; and evaluate strategies to mitigate risk. The purpose is to proactively identify transportation facilities that have a high risk of failing due to flooding so mitigation strate- gies can be implemented using available project develop- ment and funding mechanisms prior to the next disaster. These transportation resiliency plans will be developed on a watershed basis and will involve the integration of river corridor and transportation corridor planning. • Rapid culvert sizing: VTrans has developed a computer- ized process to rapidly assess culvert specifications using a variety of site-specific and hydrological data sources. This tool allows VTrans to expedite support during emergencies and to reassess the vulnerability of culverts as precipitation models with higher certainty become available. • Resilient Vermont Project: Stronger Communities, Eco­ systems, and Economies: VTrans and a wide variety of stakeholders are compiling an inventory or map of resilience- building activities already underway, creating a shared def- inition of “resilience” specific to Vermont and allowing for prioritization of a variety of actions and investments to increase resilience. As seen in this example from Vermont, adaptation strate- gies can be applied in several categories. The following sub- sections discuss adaptation strategies in other states. Planning Numerous adaptation plans recognize the general need to incorporate the changing climate into long-range planning. Florida’s Climate Action Plan, for instance, recommends that the Florida DOT should update the Florida Transportation Plan to develop long-range goals, objectives, and strate- gies for adapting to potential impacts from climate change. Likewise, California proposes to incorporate climate change vulnerability assessment planning tools, policies, and strat- egies into existing transportation and investment decisions

168 (e.g., regional planning, programming, and project planning) (Caltrans 2012). Similarly, Oregon’s Framework for Address- ing Rapid Climate Change recommended that state agencies integrate climate change preparation into existing sustain- ability plans, agency risk management plans, or other long- range plans. Maryland also recommends integration of adaptation strategies into local comprehensive plans and implementing codes and ordinances, as well as integration of adaptation strategies into state plans and underlying management and regulatory programs. Some provide more specific recommen- dations on what these long-range planning considerations might be. The City of Punta Gorda, Florida, recommends con- straining locations for certain high-risk infrastructure. The Houston–Galveston Area Council (H-GAC) recommends con- sidering the appropriateness of different modes of transpor- tation given climate change impacts and the increased costs to maintain and operate each mode, and suggests consider- ing a longer-term view of infrastructure needs over the next 50 to 100 years (in terms of maintenance, construction, and rehabilitation costs). H-GAC also recommended using alter- native paving products for higher temperatures. King County, Washington, has incorporated adaptive design strategies into planning documents such as the Transportation Needs Report and Six-Year Capital Improvement Plan. As noted earlier, the French Broad River MPO in North Carolina has undertaken one of the most extensive efforts to integrate climate change adaptation into the regional trans- portation planning process. The types of strategies identified in the climate change chapter of the long-range transporta- tion plan include the following (French Broad River MPO 2010): 1. Implement strategies to reduce risk of flooding (and other risks), including reviewing roads and bridges in flood- prone areas to ensure they are designed to handle the risk. Consider redesign to make existing structures more flood resilient. Design and construct roads and roadbeds to be resilient to flood impacts, especially based on the new floodplain maps that have been released by the state. Consider other potential hazards such as landslides and dam failures and their potential impact on transporta- tion corridors. 2. Redesign railroads to make them more resilient to climate change impacts. 3. Develop the ability to deal with greater climate variability and associated temperature extremes. Factor in budgetary impacts caused by preparation for responding to tempera- ture extremes. 4. Coordinate with the region’s local governments and plan- ning partners to link transportation with land use. 5. Use future scenarios in transportation and land use plan- ning to design systems that are robust and resilient com- pared to just being optimized for current conditions and economics. Transportation systems that are designed to operate well under a range of future scenarios are superior to a single system design tied to one view of the future. 6. Pinch points on maps to show vulnerable “hotspots” that lack options. More drought, fires, and intense rainfall amounts will produce more landslides that can be a major disruption to main transportation corridors. 7. The region’s local governments, emergency responders, and planning partners should work together to minimize the region’s reliance on gasoline distribution sites out of the region, which makes the region more vulnerable to disruption. Environmental Analysis Several states and the federal government have taken steps to incorporate adaptation considerations into environmental analysis, specifically efforts relating to NEPA documentation. In 2011, for example, U.S. DOT agencies were given policy direction by the Secretary to consider climate change impacts in their activities (U.S. DOT 2011). California is operating under a governor’s executive order that directs state agencies that are planning to construct projects in areas vulnerable to sea-level rise to consider a range of sea-level rise scenarios for the years 2050 and 2100 (California Executive Order S-13- 08). State agencies are “urged to consider timeframe, risk- tolerance, and adaptive capacity when determining whether to adapt the project for potential sea-level rise impacts” (U.S. DOT 2011). Design Standards A number of plans list changes to design standards as a needed strategy to adapt to climate change—but at this stage few provide specifics. California, for instance, recom- mends developing transportation design and engineering standards to minimize climate change risks to vulnerable transportation infrastructure. Both H-GAC and the City of Punta Gorda recommended using paver blocks (which act as a form of permeable pavement) for parking lots to address stormwater runoff and the urban heat island effect (which will be exacerbated by global warming). Among those that do get to a greater level of detail, Maine DOT rec- ommends upgrading design standards for water flow from Q50 to Q100 to build in resiliency in the face of extreme weather events. Again, King County is in the forefront here and is already incorporating climate change considerations into the project designs of bridges and culverts that are being rebuilt.

169 Infrastructure Retrofit Some plans show an awareness of the need to integrate plan- ning policy into the decision to retrofit, rather than approaching the issue from a purely engineering perspective. For instance, the Maryland plan identifies several engineering strategies for retrofitting coastal infrastructure to protect against sea-level rise, such as structural bulkheads, seawalls, or revetments. However, it also notes that larger decisions on whether to protect, relocate, or abandon infrastructure need to be made as well. In another example that addresses flooding risks, Washington State DOT’s strategies focus on restoring natural processes. This includes limiting shoreline armoring, restor- ing shorelines, and targeted removal of dikes. The Alaska Department of Transportation and Public Facil- ities has dedicated $10 million in funding to combat perma- frost thawing under highways and is also actively working on drainage improvements and evacuation routes and shelters (Arroyo 2010, Coffey 2010). Maintenance Fewer strategies have been developed for maintenance pro- cedures, although some of the design changes suggested are meant to reduce future maintenance costs. The Maine DOT has conducted a pipe and culvert vulnerability assessment, and the Maine DOT Bridge Maintenance Division completed a scour report. Based on this information, the Maine DOT is preparing bridge-specific scour plans. The Rogue River Basin, Oregon, plan recommends expanding road upgrading and maintenance such as the installation of larger culverts and regular culvert clean outs to prevent washouts during major storms and floods. Operations Although it is likely that transportation operations will change to respond to climate change—road weather programs, to name an obvious example—very few plans address opera- tions at this point (Radow and Neudorff 2011). Responding to extreme weather events in an effective manner requires not only advanced coordination of the many agencies involved, but also rapid clearing of transportation lifelines, such as roads that lead into devastated areas. As was seen in Vermont’s response to Tropical Storm Irene, the response to isolated com- munities and individual travelers required the coordinated effort of many different groups, with the state DOT playing a key coordinating and information clearinghouse role. Cali- fornia recommends incorporating climate change impact considerations into disaster preparedness planning for all transportation modes. The City of Punta Gorda, Florida, pro- vides a similar recommendation. In a different approach to the issue, the Rogue River Basin, Oregon, plan suggests linking public transportation systems as much as possible to facilitate movement of people and equipment in emergency situations. Public Outreach/Communications A major challenge with respect to shorter-term extreme weather events and longer-term climate changes is conveying to the public the actions that can be taken to respond to par- ticular events. This might entail improving road weather infor- mation systems (such as being done in Michigan) to providing information on the types of impacts climate change could have to the transportation system (such as being done in California, Maryland, and Washington). Process Recommendations Overall, it appears that most strategies identified have not yet been taken to the engineering level. This is consistent with the general state of practice of adaptation planning in the United States; given that most agencies have only started adaptation planning in the last few years, it will take some time to bring these strategies to the implementation level. It is also likely that as this happens, maintenance and operations will receive more study. As a result, some adaptation strategies included in state and local plans are really process recommendations to further adap- tation planning. For example, Florida identifies research as an immediate adaptation action. Alaska recommends creating a coordinated and accessible state-wide system for key data collection, analysis, and monitoring. Some governments have also identified the need for training and establishing criteria so agencies can better integrate climate change impacts into their planning efforts. King County, Washington, is a good exam- ple of this. The Climate Plan identified the need for training and educating the Road Services Division staff on expected changes in climate, how these changes potentially affect the facilities they manage, and how to identify adaptation solu- tions to address near- and long-term impacts. Finally, some plans show an additional focus on the need for monitoring to assess how the climate is actually changing and whether adopted adaptation strategies will therefore need to be modified. For instance, New York City’s risk-based approach to adaptation, Flexible Adaptation Pathways, is an iterative process that recognizes the multiple dimensions of climate hazards, impacts, adaptations, economic develop- ment, and other social factors. This iterative process is pred- icated on the establishment of climate change monitoring programs that can provide feedback to the process to allow for changing “pathways.” The adaptation strategies studied by King County’s Road Services Division provides an illustrative example of the range

170 of adaptation strategies an individual transportation agency might consider: • Replacing or rehabilitating bridges in order to improve floodwaters conveyance and to avoid scour during high flows • Using pervious pavement and other low-impact devel- opment methodologies to manage stormwater through reduced runoff and on-site flow control • Modifying existing seawalls to avoid failures in transporta- tion facilities • Evaluating roadways to minimize their vulnerability to potential risk from landslides, erosion, or other failure triggers • Developing new strategies to effectively respond to increas- ingly intense storms, including providing alternative trans- portation access • Managing construction and operations to minimize effects of seasonal weather extremes • Identifying opportunities to incorporate habitat improve- ments that buffer the effects of climate change on eco- system health into project designs. 5.4.2 International Adaptation Strategies Of the international reports reviewed, only three provided strategies for dealing with climate change impacts to road- way networks. And in most cases, the strategies were gen- eral calls for additional research in design and maintenance practices. Canada As The Road Well Traveled: Implications of Climate Change for Pavement Infrastructure in Southern Canada put it, “The key adaptation issues will surround not how to deal with potential impacts, but rather when to modify current design and maintenance practices,” and the report recommends that study results should be discussed in the engineering commu- nity to move from exploratory research to practical guidance (Mills et al. 2007, p. 65). The Canadian Council of Professional Engineers’ report, Adapting to Climate Change: Canada’s First National Engi- neering Vulnerability Assessment of Public Infrastructure, which looked at the impacts of climate change on four types of infra- structure, classified its conclusions into seven themes and five recommendations—none of which call for far-reaching design approaches or solutions (PIEVC 2008): • Themes – Some infrastructure components have high engineering vulnerability to climate change. – Improved tools are required to guide professional judgment. – Infrastructure data gaps are an engineering vulner- ability. – Improvement is needed for climate data and climate change projections used for engineering vulnerability assessment and design of infrastructure. – Improvements are needed in design approaches. – Climate change is one factor that diminishes resiliency. – Engineering vulnerability assessment requires multi- disciplinary teams. • Recommendations – Revise and update the Engineering Vulnerability Assess- ment Protocol. – Conduct additional work to further characterize the vulnerability of Canadian public infrastructure to cli- mate change. – Develop an electronic database of infrastructure vul- nerability assessment results. – Assess the need for changes to standard engineering prac- tices to account for adaptation to climate change. – Initiate an education and outreach program to share results of this assessment with practitioners and deci- sion makers. An important point made in the report is that many of the potential impacts of climate change can be alleviated through improved system preservation activities and that climate change is only one factor that diminishes resiliency. “In recent years, concerns have been raised in Canada about the present levels of maintenance and future needs for infrastructure. . . . Climate change is likely to intensify the engineering vulnerability if current levels of maintenance continue. Properly maintained infrastructure enables the infrastructure and its components to function as designed, which includes accounting for changing climate events” (PIEVC 2008, p. 68). Canada’s Confederation Bridge—an 8-mile (13-kilometer) bridge between Borden, Prince Edward Island, and Cape Tor- mentine, New Brunswick—is an example of a completed proj- ect that took climate change into account during the planning and design phase. The bridge, which replaced an existing ferry connection, consists of a high-level two-lane road structure built on piers over the entire crossing of the Northumber- land Strait. It provides a navigation channel for ocean-going vessels with vertical clearance of about 164 feet (50 meters). During the planning and design process, which was begun in 1985, sea-level rise was recognized as a concern. So that vertical clearance could be maintained into the future, the bridge was built 1 meter higher than was currently required to accommodate sea-level rise over its hundred-year lifespan. The bridge opened to traffic in 1997.

171 Scotland The Scottish Road Network Climate Change Study also emphasizes this point in its discussion of the impacts of pre- dicted climate change factors on the road network. The impact of heat on roadway rutting is frequently mentioned as a cli- mate change concern. However, the report observes that “most rutting problems on the trunk road network are the result of pavement failure due to the volume of heavy goods vehicles” (Scotland Ministry of Transport 2005, p. 62). Impacts of road- way flooding due to increased amounts or intensity of rain- fall are also an often-mentioned climate change concern. But, as the report notes, “the most common cause of flooding in areas where drainage is present is due to detritus washing into the system, resulting in partial or complete blockage” (p. 65). The report posits that “The effective maintenance of water- courses and ditches is essential to the operation of culverts and it is recommended that measures to target areas where known problems exist through preemptive clearing of detritus in advance of predicted heavy rainfall should be considered by all maintaining authorities” (p. 68). It also recommends, given the expected changes in rainfall, that the design storm be amended from a return period of between 1 in 100 years to 1 in 200 years (p. 67). The Scottish Road Network Climate Change Study was the only report that discussed the impact of a lengthened grow- ing season on the roadway network. It notes that in recent years it has been necessary to cut roadside grasses three times a year, up from two cuts a year. At most locations, landscape maintenance requires traffic management, which affects the traveling public. To offset the potential effects of a longer grow- ing season, “it is recommended that slow-growing elements are used where appropriate, in order to minimize the extent of cyclic maintenance required” (Scotland Ministry of Trans- port 2005, p. 63–64). The report also notes that many roadway risks associated with severe weather, which is predicated to increase under climate change scenarios, cannot be completely eliminated through design but should be addressed through ongoing road user education. These include conditions that result in poorer skidding resistance (such as heavy rains, roadway flooding, and winter conditions); reduced visibility due to fog; and unexpected forces being applied to vehicles in high-wind conditions. The report suggests that “ongoing road user edu- cation is an essential component in raising the awareness of the need to modify behavior during severe weather events. It is also considered that the provision of relevant information to road users in respect of such events would assist in encourag- ing modified behavior” (Scotland Ministry of Transport 2005, p. 76). In fact, the only condition in which large-scale adapta- tion strategies are suggested relates to coastal flooding situa- tions and even then it proposes other approaches—including user education—first. “Areas at risk may then be addressed through a combination of warning signage, edge strengthen- ing, or introducing sea-defenses. In extreme cases, consider- ation could be given to whether re-routing is appropriate. It is also recommended that any new projects proposed in low- lying areas should be reviewed with respect to these risk fac- tors, to enable appropriate decisions to be taken at the design stage” (p. 75). 5.4.3 Asset Management Systems and Climate Change Adaptation Transportation asset management (TAM) is defined as “a strategic approach to managing transportation infrastructure . . . focusing on business processes for resource allocation and utilization with the objective of better deci- sion making based upon quality information and well- defined objectives”(AASHTO 2011). As agencies increasingly adopt TAM strategies, opportunities exist to integrate con- sideration of weather risk into TAM objectives, data collec- tion, performance measurement, monitoring, and resource allocation decisions. Over time, the integration of weather and climate information into TAM will help agencies make targeted investments or allocation decisions to increase the resilience of the network and of individual assets to extreme weather events (Meyer et al. 2012b). State DOTs have long planned for fluctuations in the cost and timing of construction, availability of funding, and development of new regulations. However, extreme weather risk deserves spe- cial consideration because certain types of extreme weather are becoming more frequent and intense. Figure II.14 shows how extreme weather and climate change considerations could be incorporated into an asset manage- ment goals structure. No significant restructuring of the TAM framework is needed to integrate climate change/extreme weather considerations into asset management systems. The spatial nature of much of the data used in TAM systems, com- bined with the results of risk analysis, can provide DOT offi- cials with good indications of where potential problems exist. A more detailed discussion of integrating climate change and extreme weather considerations into asset management systems can be found in the Practitioner’s Guide (Part I of this volume) and in Meyer et al. (2010). In addition, two of the climate adaptation pilot studies supported by the FTA focus on the integration of climate change onto transit asset manage- ment systems. 5.5 Summary This chapter has described the different types of climate change impacts that are likely to affect the nation’s road system, both in terms of road design and operations/maintenance. The

172 impacts are wide ranging, as are the types of adaptation strat- egies that can be considered. As shown in the Vermont case, and indeed in examples from other states, climate change and extreme weather events can be considered in many of the tra- ditional agency functions—planning, environmental analy- sis, design, infrastructure retrofit, construction, operations, maintenance, emergency response and public outreach and communications. Of particular interest is the potential that asset management systems have in serving as a foundation for considering climate change impacts and needs as part of an agency’s decision-making process. By considering asset man- agement systems for such a platform, an agency puts in place an approach that is already well established in most transpor- tation agencies and that allows climate change and extreme weather factors to be placed within a decision-making context that is familiar to agency officials. Goal • Increase resilience of the transportation system to high priority risks Objectives Performance Metrics Data Collection • Prioritize investment to target critical assets at high risk • Monitor weather risk over time and take mitigation action when critical risk thresholds are met • Percent of assets at high risk due to weather impacts • Total replacement value of assets at high risk due to weather impacts • Annual and monthly cost of repair needed in response to extreme weather • Conduct vulnerability and risk assessments to define priority risks • Develop risk ratings and assign to each asset • Collect data on costs incurred during extreme weather events, could include repair costs, delays, etc. • Track assets experiencing repeated problems due to extreme weather Source: Meyer et al. (2012b). Figure II.14. Integration of extreme weather concerns into asset management.

173 6.1 Introduction Most agencies that are concerned about adaptation begin by conducting a risk assessment of existing assets. Most of these risk assessments remain largely qualitative and based on professional judgment. This will likely remain the case until more probabilistic climate projections become avail- able. Some risk assessments to date have shown the highway system to have only modest vulnerabilities to climate change. Others have indicated enough cause for concern to recom- mend that action be taken. Whether an agency chooses to take action depends on their fiscal and political capacity to effect change and their level of tolerance for risk. It is quite possible that separate agencies, facing the same risks, might choose very different courses of action, especially absent any set of national or industry standards. The Practitioner’s Guide (Part I of this volume) devotes a chapter to risk assessment tools and approaches and will not be repeated here. However, the following sections provide an overview of how risk can be viewed in the context of climate adaptation planning. 6.2 Risk Assessment Defined An asset is vulnerable to climatic conditions if these con- ditions (such as intense precipitation and extreme tempera- tures) and their aftermath (such as a flood exceeding certain stages and consecutive days of higher than 100°F tempera- tures) result in asset failure or sufficient damage to reduce the asset’s functionality. The vulnerability can thus be measured as the probability that the asset will fail given the occurrence of climate stressors (e.g., “there is a 90 percent chance the bridge in its current condition will fail with a 500-year flood”). Vul- nerability primarily focuses on the condition of the asset. Climate-related risk is more broadly defined in that risk can relate to impacts beyond simply the failure of the asset. It relates to the failure of that asset in addition to the con- sequences or magnitudes of costs associated with that fail- ure (Willows and Connell 2003). In this case, a consequence might be the direct replacement costs of the asset, direct and indirect costs to asset users, and, even more broadly, the eco- nomic costs to society given the disruption to transporta- tion caused by failure of the asset or even temporary loss of its services (e.g., a road is unusable when it is under water). The importance of broader economic costs to the risk analy- sis should not be underestimated. For example, if a bridge is located on the only major road serving a rural commu- nity and there is a possibility that the bridge could be washed out with major storms, the measure of consequence should include the economic impacts of isolating that community for some period of time while the bridge is being replaced. Putting it all together, the complete risk equation is thus: Risk = Probability of Climate Event Occurrence × Probability of Asset Failure Given a Climate Event Occurrence × Consequence or Costs The risk equation shows that low-probability climate events (e.g., a Category 5 hurricane hitting the community) with high probabilities of asset failure and high consequence costs could still have high risk scores. Likewise, events with lower consequence costs, but greater probability of occurrence or conditional failure, could lead to similarly high risk scores. Most transportation-related climate change risk assessments performed to date have embraced this general risk concep- tualization involving likelihoods of climate events occurring, probability of asset failure, and magnitude of the consequence. According to the FHWA, “a risk assessment integrates the severity or consequence of an impact with the probability or likelihood that an asset will experience a particular impact. To determine consequence, transportation agencies may wish to consider the level of use of an asset, the degree of redundancy in the system, or the value of an asset (in terms of cost of replacement, economic loss, environmental impacts, cultural C H A P T E R 6 A Focus on Risk

174 value, or loss of life)” (FHWA 2012a). The FHWA’s concep- tual framework (see Figure 4) incorporates a risk assessment component. The risk analysis is to be conducted on assets of high importance and to consider only those changing climate variables where there is either (1) a high likelihood and high magnitude of impact, (2) a high likelihood but low magni- tude of impact, or (3) a low likelihood but high magnitude of impact. The vulnerability of each important asset is then to be evaluated based on how it has responded to historical changes in the climate variable in question and to associated extreme weather events. The costs of any repair or service disruptions are to be noted and a determination made as to the capacity of the particular asset to withstand the projected future changes in the climate stressor. From here, important assets that history indicates have a medium or high vulner- ability to projected climate changes are carried forward for further risk analysis. Low-vulnerability assets are to be noted and marked for future monitoring. The FHWA framework identified three characteristics of asset vulnerability that are key to understanding the level of risk attached to particular climate stresses for specific assets— sensitivity, exposure, and adaptive capacity. 6.2.1 Sensitivity One of the first steps in a risk analysis is determining how an asset fares when faced with different climate stressors, called “sensitivity.” Asset condition would be expected to be an important determining factor to an asset’s sensitivity to stresses. In the cases of sea-level rise, storm surge, or riverine flood inundation, sensitivity is likely to be relatively straight- forward and determined by the key thresholds where facilities become inundated. For bridges, the minimum elevation of the critical elements such as low points of approach road- ways or deck or low chord elevations of the bridge could be used to help with this assessment. The sensitivity of rails and pavements to extreme heat and the sensitivity of bridges to strong winds would likely require close coordination with asset owners to ascertain critical thresholds. 6.2.2 Exposure Once sensitivity is defined, the exposure of the asset to the climate stresses projected for the region given different emission scenarios needs to be determined. For most of the climate stressors, exposure could be determined through a GIS analysis overlaying the transportation network onto the climate projection information. The degree to which an asset is exposed to different stresses would be assessed. This might consist of the maximum depth of flooding or, for tempera- ture and wind stressors, how high over the facility’s sensitivity threshold the projected future value is. Whether the facility was affected by any recent extreme weather events would also be flagged. When considering exposure to permanent sea-level rise, storm surge, and riverine flooding inundation, special care should be taken to ensure that inundation could realistically occur at each facility and that false positives (e.g., bridges and roadways that are elevated and thus not likely affected by rising water levels) are identified. This will likely require a visual assessment of the key assets in the GIS data sets. Special approaches will also be required for tunnels because a straight- forward GIS analysis of subterranean road and transit lines will not necessarily capture the possibility of water entering tunnels through ventilation systems and other access points. 6.2.3 Adaptive Capacity Adaptive capacity, the ability of the transportation facility and network to cope with the consequences of exposure, is another key component of vulnerability. An important con- cept when assessing adaptive capacity is the redundancy of the transportation network; the greater the network redundancies, the greater the ability of the transportation system to absorb the loss of use of a given facility affected by climate stressors (i.e., the higher its adaptive capacity). On the highway network, redundancies may take the form of alternate routes that peo- ple can use to detour around compromised facilities. A typical approach to analyzing the redundancy component of adaptive capacity is to consider the daily cost of the additional travel time required by different types of facility users (e.g., drivers, bus and rail passengers, freight movements) when taking an alternative mode or detour route. The daily cost of additional travel time would most often be assessed with the aid of a regional travel demand model, which covers the entire project study area based on network detail. By removing the climate stressor–compromised links in the model, the optimal detour routes for travelers and the implications of those detoured trips on congestion can be ascertained. Short-term transportation recovery mitigation plans, such as reconfigured highway rout- ings and transit service plans, could be directly modeled with the model. The model would forecast travel demand changes, including diversions to alternate highway routes and transit facilities, quantifying the implications of the revised travel pat- terns in terms of congestion impacts, travel times, and other user costs. This would highlight routes that, if affected, might have significant ripple effects throughout the network. Another component of adaptive capacity is how long it takes to restore service to the facility once it has been compromised: the longer the restoration time the lower the adaptive capacity and the higher is that facility’s vulnerability. Restoration time (to be measured in days) can be considered a multiplier to the additional user costs associated with detours. In other words, each day of expected downtime can be multiplied by the user

175 costs to arrive at a better representation of user costs if there is a failure. Restoration times might be as little as a day or two for temporary flooding where permanent damage is not expected or weeks for assets like tunnels and electronic rail infrastruc- ture that require major restoration efforts. Replacement costs are the final component of adaptive capacity that needs to be considered in the vulnerability anal- ysis. The costs to replace or repair a compromised asset are an important component of the adaptive capacity from an asset owner’s perspective. Thus, all else being equal, larger trans- portation investments with higher replacement/repair costs can be considered to have a higher vulnerability worthy of greater prioritization for adaptive action. High-level replace- ment and repair costs for each facility can be estimated based upon standard cost-estimating procedures, historical experi- ences, and consultation with asset owners. These repair and replacement costs would be added to the user costs discussed previously to arrive at a vulnerability score (in dollars) for each asset. If this analysis is being used to compare vulner- ability levels among a number of assets (to determine priori- ties), a normalization scheme could be employed to ensure that the scores are comparable across facilities. Adaptation options can then be considered for high- or medium-risk assets while low-risk assets are given lower pri- ority for the time being. 6.3 Approaches to Risk Assessment Several adaptation plans illustrate some of the tools and processes for risk assessment that have been developed by various states and localities. Both King County, Washington, and New York City provided tools primarily meant to assist staff in their own agencies in structuring risk and vulnerabil- ity assessments but also designed to be generic enough to be used by other localities. For instance, King County’s Prepar- ing for Climate Change: A Guidebook for Local, Regional, and State Governments provides a checklist and recommendations for conducting vulnerability and risk assessments (Center for Science in the Earth System and King County 2007). Other agencies have already made use of these tools—most notably, A Framework for Climate Change Adaptation in Hawaii was based directly on the King County guidelines. The New York City Panel on Climate Change’s Adaptation Assessment Guidebook also contains tools to help stakehold- ers. For instance, like King County’s Preparing for Climate Change, the Adaptation Assessment Guidebook provides sector- specific infrastructure questionnaires to guide the assessment process and create an inventory of infrastructure at risk to cli- mate change impacts. It also provides a risk matrix, a tool to help categorize and prioritize the risk assessment findings by facility, based on the probability of the climate hazard, likeli- hood of impact, and magnitude of consequence. These and similar studies resulted in a qualitative assess- ment of the risks associated with specific transportation assets. Figure II.15 from Adapting to Rising Tides is a good example of how this approach is portrayed (Metropolitan Transportation Commission, Caltrans, Bay Conservation and Development Commission, 2011). Such a framework has been used to con- duct initial, high-level risk assessments that identify the major climate drivers most likely to impact a given agency’s infra- structure, the types of infrastructure most vulnerable, and discuss the kinds of impacts that might be expected. Source: Metropolitan Transportation Commission, Caltrans, Bay Conservation and Development Commission (2011). High Risk (Red) Figure II.15. Example risk assessment from the San Francisco Bay Area.

176 Most of the risk assessments reported in the literature have primarily focused on the water-related impacts: sea-level rise, flooding, intense tropical storms, and intense precipitation. Threats to evacuation routes have also been assessed in many coastal locations. Fewer have focused on temperature itself as a major issue for highway systems, although some have included air quality and heat island concerns. For instance, the transportation vulnerabilities identified in Hawaii include threats to transportation infrastructure (evacuation routes) due to sea-level rise and storm flooding; weakening of infra- structure due to repetitive and prolonged stress (dams, roads, bridges, tunnels, storm drains); and submersion of vital trans- portation infrastructure due to sea-level rise and flooding. Alaska identified a unique set of vulnerabilities that do not exist in the other 49 states, particularly infrastructure damage from permafrost thaw and severe coastal erosion from lack of sea ice armoring. The emphasis on water-related risk assessment is perhaps not surprising. These parameters are both more pressing and somewhat easier to identify for most agencies due to the (relative) simplicity of comparing infrastructure elevation to sea-level rise scenarios. For instance, California’s Preliminary Transportation Assessment identified the number of miles of highway that would be inundated by a 55-inch sea-level rise, by county and road. Few agencies have gone to the point of systematically inven- torying their assets to identify how each transportation link or facility will be affected by climate change. Nonetheless, as states have finished the initial round of adaptation planning, some have begun the process of identifying vulnerabilities to their transportation infrastructure in a more comprehensive man- ner. For instance, California and Maryland DOTs have con- ducted in-depth assessments of the vulnerability of their road systems. Washington State DOT (WSDOT) has also conducted a vulnerability assessment of WSDOT-owned infrastructure. The process of identifying vulnerable assets and then assigning risk values to them is likely to be a collaborative process, including a range of participants (Slater 2011). Mary- land provides an illustrative example of a state implementing the systems needed for a more detailed risk inventory. It is one of the first states to begin systematically inventorying the vulnerability of its transportation assets to climate change, beginning with vulnerability to sea-level rise. Sea-level rise is an initial priority for Maryland’s adaptation plan because of that state’s particular vulnerability: it has more than 4,000 miles of coastline, much of it low-lying land on the Chesapeake Bay at risk to inundation (in fact, in the past cen- tury several islands in the Bay disappeared under the rising water levels). As a result, the Maryland adaptation plan rec- ommended the integration of coastal erosion, coastal storm, and sea-level rise impacts into existing state and local policies and programs. To that end, the state has pursued several initiatives in part- nership with universities, non-government organizations (NGOs), and NOAA. For instance, the Coast-Smart Commu- nities Initiative provided funding and technical support to towns in coastal counties to prepare for sea-level rise, coastal erosion, and storm inundation. More concretely, the state has developed a high-resolution LiDAR data set to allow devel- opment of sea-level rise inundation models along its coast- lines. This data set has been made available to the public as the Maryland Coastal Atlas, including maps of sea-level rise vulnerability areas (viewable with the Coastal Atlas Shoreline mapping tool). State-wide Sea-Level Rise Vulnerability Maps have been created for 14 coastal counties, depicting lands at potential risk. These maps show lands at three elevations (i.e., 0 to 2 feet, 2 to 5 feet, and 5 to 10 feet) above mean sea level. The use of LiDAR data allowed the Maryland Coastal Atlas to map sea-level rise with more precision than was found in two previous reports on mid-Atlantic sea-level rise by the U.S. Climate Change Science Program (CCSP) or U.S. DOT, making it the most advanced sea-level rise resource for the mid-Atlantic region (see Figure II.16). Not all locations possess these data and can do analyses at this resolution: the CCSP reports that it may be some time before the rest of the mid-Atlantic region has comparable LiDAR elevation data that are suitable for detailed assess- ments of sub-meter increments of sea-level rise. One potential use of the mapping tool is to identify coastal areas subject to coastal flooding from storm inundation and sea-level rise for long-range planning, floodplain management, and emergency management. Using this data set, the Maryland State Highway Administration is currently building a new shoreline data set as a polygon for GIS mapping to determine which assets are located within the zone of inundation. These data will eventu- ally be compiled into an overall Maryland DOT assessment of Maryland’s critical transportation facilities and the system’s vulnerability to projected sea-level rise and extreme weather damage. In addition, the Maryland State Highway Administra- tion and the Maryland Transportation Authority (which has responsibility for the state’s toll facilities) are in the process of developing a joint climate change adaptation policy and an accompanying implementation strategy. The overarching policy goal of the effort is to continue to cost-effectively main- tain the safety and serviceability of Maryland’s highway system as the state’s climate changes. This policy will be implemented with a four-part strategy that includes (1) taking practical oper- ations, maintenance, and administrative actions to respond to and limit damage from extreme weather events that are already occurring and may worsen with time; (2) developing a stron- ger understanding of the longer-term threats to the state’s highway network posed by a changing climate; (3) develop- ing approaches for adapting existing infrastructure to climate

177 changes as an improved understanding of risks develops; and (4) considering adaptation for new projects to increase their resiliency to potential climate impacts. Seventy detailed action items have been developed to implement this four-part strategy. These include a number of “no-regrets” operations actions that will improve the agen- cies’ response to severe weather events. Operations actions include, among other things, better planned and managed detour routing and installing battery back-up power at all sig- nals that would require a traffic officer if there was an outage. The action items also include maintenance activities that, to the extent possible, prevent impacts from occurring in the first place. These include electronic tracking and mapping of work orders to identify areas of recurring problems and stream- lining environmental permitting to allow for quicker debris removal in culverts and underneath bridges. Other action items call for conducting risk analyses of existing facilities throughout the state (in coastal areas and beyond) and the development of procedures for incorporating adaptation into the siting and design of new facilities and major rehabilita- tions. Responsibility over each of the 70 action items has been delegated to specific departments within the DOT ensuring that adaptation will become an agency-wide concern. One of the most recent tools developed for sea-level rise analysis comes from the Florida DOT and is called the Flor- ida Sea-Level Scenario Sketch Planning Tool (Thomas et al. 2013). The tool is intended to be used primarily at the state and regional levels. The sea-level projection rates were con- sidered “low,” “intermediate,” and “high.” Low rates were esti- mated by simply extending historical rates of sea-level rise into the future target years (2040, 2060, 2080, and 2100). Intermediate and high projected rates were taken from sce- narios developed by the USACE. The estimated sea-level rise anywhere along the Florida coast for the target years was tied Source: Maryland Coastal Atlas Shoreline mapping tool. Figure II.16. Sea-level rise analysis in Maryland.

178 to the expected increase in sea levels at existing tidal gauges. A state-wide digital elevation model was developed by combin- ing information from four existing digital elevation model databases for the state. The transportation database layer was developed from the state DOT’s existing road and bridge inventory. Inundation scenarios were then created by super- imposing the sea-level rise elevation with the digital elevation model (Figure II.17), and vulnerable transportation facilities were then identified by tying the rising water levels to the elevation of transportation facilities. This tool provides an important capability to state and local officials who want to identify vulnerable areas and facilities in their jurisdiction. Given the GIS platform of the tool, eventu- ally the analyses can be conducted that link inundation areas with critical community and economic areas, populations of concern, high-value facilities (such as emergency manage- ment offices or hospitals), and evacuation routes. This would add the element of risk analysis into the tool capability. Internationally, a synthesis by Wall and Meyer (2013) showed that risk frameworks were almost always based on internation- ally or nationally adopted procedures for risk assessment. Inde- pendent and private-sector transportation organizations (i.e., port authorities, airports) frequently reported that enterprise risk management was already a part of their existing business management activities and that climate change adaptation planning would be incorporated into these existing practices. For example, in the United Kingdom, both the Port of Dover (2011) and NATS (2011)—an air traffic control organization— noted that the International Organization for Standardiza- tion standard ISO 31000:2009, Risk Management—Principles and Guidelines, was used in developing their risk management programs. In Canada, the Ontario Ministry of Municipal Affairs & Housing (Bruce et al. 2006) and Natural Resources Canada (Canadian Institute of Planners 2011) both reported that the standard CAN/CSA-Q850-01, Risk Management: Guidelines for Decision Makers, was used in developing their frameworks; the Halifax Regional Municipality (Dillon Consulting and de Romilly & de Romilly Limited 2007) used an earlier edition of the same standard, as well as CAN/CSA-Q634-M91, “Risk Analysis Requirements and Guidelines.” Frameworks in Australia and New Zealand (CSIRO et al. 2007, Gardiner et al. 2008, Gardiner et al. 2009) were predomi- nantly informed by AS/NZS 4360:2004, Risk Management, and the superseding standard AS/NZS 31000:2009. This latter stan- dard is also specified as ISO 31000:2009, which was used in the development of the Risk Management for Roads in a Changing Climate framework in the European Union (Bies et al. 2010). Australia’s Climate Change Impacts & Risk Management: A Guide for Business and Government is a good example of how risk is viewed in other countries. This guide recommends that risk identification, analysis, and evaluation be conducted (a) Florida inundation from sea-level rise, 2060 (approximately 28 inches) (b) Florida inundation from sea-level rise, 2100 (approximately 62 inches) Source: Inundation mapped using the USACE High Curve (Circular EC 1165-2-12) and NOAA Key West tide gauge data, Mean Higher High Water; Inundation map: University of Florida GeoPlan Center, 2013; Imagery (background image): Esri, DigitalGlobe, GeoEye, I-Cubed, USDA, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community. Figure II.17. Florida inundation from sea-level rise, 2060 and 2100.

179 by risk element, that is, discrete elements or areas facing the organization (Commonwealth of Australia 2006). This can provide focus to the discussion and help participants more efficiently look at and understand potential risks. The recom- mended process is as follows: Step 1: Brainstorm risks associated with the element until the main issues are felt to have been exposed. Step 2: Taking each risk in turn: a. Identify any existing controls (features of the envi- ronment, natural and manmade structures and mechanisms, procedures and other factors) that are already in place and tend to mitigate the risk; b. Describe the consequences the risk would have if it was to arise, given the controls, and in each of the scenarios under consideration; c. Describe the likelihood of suffering that level of consequence, again given the controls, in each of the scenarios under consideration; d. Assign an initial priority in each scenario based on the likelihood and consequence of the risk; and e. Where two or more scenarios are being considered, consider adjusting the priority in recognition that some scenarios are less likely to occur than others. Step 3: Return to Step 1 for the next key element. Climate Change Impacts & Risk Management provides six principles (gleaned from climate change adaptation processes) for treating climate change risk: • Achieve balance between climate and non-climate risks • Manage priority climate change risks • Use adaptive management • Look for win-win or no-regrets treatment options • Avoid adaptation constraining decisions • Review treatment strategy Another perspective on risk and adaptation strategies is presented in Figure II.18, the Willingness Diagram from the Scottish Road Network Landslide Study (Winter et al. 2008). This figure shows the trade-offs between willingness to accept (or tolerate) risk, willingness (and/or ability) to pay, and will- ingness to alter the environment in the pursuit of lower risk. How a managing agency views each one of these factors will influence where a particular project falls in the triangle. At present, when it comes to roadway infrastructure, projects seem to fall at the upper point of the triangle—a high willing- ness to accept risk and a low willingness to pay. This may be partly driven by the fact that the risks seem low and there are low-cost, incremental approaches available. Of interest to the consideration of risk in adaptation plan- ning, the Wall and Meyer synthesis noted that “the way risk is perceived and characterized was the second most commonly listed limitation or barrier (after data limitations). Numerous agencies noted that it was difficult to define acceptable levels or risk, relevant types of risks, and the critical thresholds of risk” Wall and Meyer (2013). Furthermore, in the decision- making process, difficulty was noted in linking the immediate need for action with risks that are perceived to be of long- term or distant consequence. Effectively linking risk levels to the decision-making process was further compounded by what many agencies discussed as the qualitative treatment of risk, that is, a reliance on expert opinion and risk matrices. Chapter 4 of the Practitioner’s Guide (Part I of this volume) discusses different approaches for conducting risk assessment in climate adaptation planning. 6.4 Summary This chapter has presented an overview of one of the most important concepts in adaptation planning. Risk assessment allows transportation officials to identify which vulnerable assets are most important from both the perspective of trans- portation system performance and to an asset’s contribution to larger goals, such as economic activity and public safety. Risk is defined as the probability of climate event occurrence multiplied by the probability of asset failure multiplied by the consequence or costs of failure. Thus, as noted in the chap- ter, a high-risk asset could be one in which one or more of these factors have high values. For example, an asset with a low probability of occurrence and low probability of failure would still achieve a high level of risk if the consequences Source: Winter et al. (2008). Figure II.18. The risk domain from Scotland’s landslide study.

180 of failure are traumatic or result in huge economic costs. By considering these factors and the role that assets play in the transportation systems, transportation officials can identify where investment should occur to limit the risk associated with such failure. Although the definition of risk above includes some indi- cation of probable occurrence, in reality, such probabilities are hard to formulate, especially when considering that the occurrence in question might not be real until many years into the future. To account for this uncertainty, most studies have relied on qualitative or subjective assignment of risk. Thus, “high,” “medium,” or “low” is often used to indicate the level of risk associated with individual assets. Even those approaches considered more quantifiable use ordinal rank- ings of values, that is, “1,” “2,” or “3” to indicate relative risk. The intent of these approaches is straightforward—to pro- vide decision makers with some sense of where investment in the transportation system would provide the greatest reduction in risk associated with climate change–related disruptions.

181 7.1 Introduction During the course of this research, the United States expe- rienced several extreme weather events that caused severe disruption to the transportation system and in several cases significant damage (e.g., Superstorm Sandy, Hurricane/Tropical Storm Irene, extreme heat events in the Midwest and Southwest, flooding in the Midwest, and unexpected major snow storms in New England and the Mid-Atlantic). Because of these events, many transportation agencies and related associations (such as the AASHTO) have focused attention on how agencies could prepare for, manage agency operations during, and recover from weather events that exceed normal ranges of severity and impacts. Although climate science does not yet definitively link these extreme weather events to a changing climate, such events are of the kind that many climate scientists believe will charac- terize future weather more so than evident today. This chap- ter examines some of the recent experience with extreme weather events and provides a checklist of steps transporta- tion agencies can take to organize themselves for dealing with the transportation-related impacts of such events. 7.2 Extreme Weather Events and Transportation Agency Operations According to the FHWA, extreme weather events refer to “rare weather events that usually cause damage, destruction, or severe economic loss. Extreme weather events include heavy precipitation, a storm surge, flooding, drought, windstorms, extreme heat, and extreme cold.” (FHWA 2012a). Transporta- tion agencies have been dealing with extreme weather events ever since agencies were given responsibilities for managing the operations of transportation systems. A great deal of experience exists in the transportation profession on how to anticipate the disruptions due to weather events and how to provide capabilities so that the transportation system can recover from any disruptions. However, state transportation officials at a 2013 symposium on extreme weather events and related transportation impacts noted that in many parts of the country the frequency and severity of such events have seemed to increase, infrastructure damage and community costs have risen, the impact of recov- ery costs on maintenance budgets and on regular operations activities continues to become more significant, and perhaps most importantly public expectations of a transportation agency’s ability to recover the transportation system quickly and efficiently have increased greatly (AASHTO 2013). In several instances, the recurring pressures on state transportation offi- cials to prepare for, manage, and recover from extreme weather events have caused organizational change, development of new management responsibilities (e.g., emergency management officials), modification of standard operating procedures, and staff training in managing and administering recover efforts. A transportation agency’s role in an extreme weather event can be divided into three major phases: pre-event planning, management of the transportation system during the extreme event, and post-event activities and lessons learned. Table II.6 shows the types of strategies and actions that state transporta- tion agencies have taken in response to extreme weather events during each of these phases. These strategies and actions were distilled from case studies of agencies’ responses to extreme weather events presented at the AASHTO symposium men- tioned earlier, as well as presentations made by transportation officials in other meetings. As reported in the Practitioner’s Guide (Part I of this volume), Lockwood (2008) suggests that changing climatic and weather conditions lead to several actions that transportation agencies should consider: • “Improvements in surveillance and monitoring must exploit a range of potential weather-sensing resources— field, mobile, and remote. • “With improved weather information, the more sophis- ticated, archival data and integration of macro and micro C H A P T E R 7 Extreme Weather Events

182 Strategy or Acon State Pre-event Planning Develop meline of likely agency response acons. Establish clear command and control structure for emergency response; develop lines of authority with other agencies. Arizona, Vermont Develop an emergency response manual, inventory lists, contact informaon, and three ered response and distribute “smart technology” with required forms and soware in order to be beer prepared for the next emergency. Compile a contractor registry database, develop a standardized electronic contract processing system, develop an emergency administrave packet for incident command centers, develop an emergency administrave packet for contractors, develop an emergency waiver process, explore alternave emergency contracng processes, and review and standardize the process for paying contractors. Develop and maintain an acve distribuon list of cell phones, explore the use of cloud technology, formulate a recommendaon for data storage during emergency response, explore and develop connecvity with data sets, explore the use of informaon technology applicaons (511, Google, etc.) for emergency response, develop a process to track equipment and materials from contractors, and standardize data collecon and data integraon. Vermont Pre purchase (e.g., traffic cones for police vehicles) and pre posion (e.g., replacement culverts). Minnesota, Colorado Review administrave policies for staff acvies (e.g., hotels/food/local transportaon charges). Develop conngency plans for specialized equipment (e.g., expanded number of contracts for crical roads, and essenal supplies such as road salt for winter storms). Improve agency wide situaonal awareness of weather event and its impacts. District of Columbia (D.C.) Increase emphasis on storm drainage maintenance and debris removal. Colorado Increase public awareness of what they should do in an extreme weather event. Partner with other agencies/conduct workshop on how to respond to extreme weather event. Arizona Establish protocol for use of traveler warning strategies [e.g., 511 traffic informaon system (online and phone), overhead electronic message boards, Twi„er and Facebook, wireless emergency alerts, mobile apps and real me roadside alert systems]. Arizona, Iowa, Washington Provide emergency response training to agency staff. Alabama, D.C., Vermont Coordinate with other states to establish mulstate strategy for responding to weather events. Implement maintenance decision support systems for extreme weather event planning. Iowa, Michigan Establish clearly defined detour routes and detour route operaons strategy. Missouri, Washington Develop and/or understand evacuaon procedures. Iowa During Event System Management Document acons taken and resources used (will be needed for post event reimbursements). Minnesota, New Jersey, D.C. Establish or use current incident command center. Establish close coordinaon with law enforcement to close roads. Have in place strategy for using resources that come from other jurisdicons. Use taccal response teams to invesgate seriously impacted areas. Ulize a variety of communicaons strategies for traveling public and other stakeholders (e.g., media releases and interviews, internet announcements, e mail alerts, local meengs and briefings, site impact tracking tool, and road closure maps on the internet). Minnesota Table II.6. State transportation agency strategies for extreme weather events.

183 Strategy or Acon State During-Event System Management (con nued) Establish corridor DOT staff patrols to monitor road damage. Prepare “Road Closed” signs and place them in consultaon with law enforcement and communicaons specialists. Colorado Ulize resources to provide real me monitoring of extent of damage or threat (e.g., Minnesota used state police helicopter to monitor flood levels). Use Google Earth with custom layers (inundaon levels, LIDAR, historical imagery, etc.) (Iowa). Iowa, Minnesota Engage the resource agencies, USACE, and the FHWA early and throughout the event. Coordinate with emergency responders and keep them updated on closures and openings throughout the event. Ulize an electronic Detailed Damage Inspecon Report (DDIR). Iowa Post-event Recovery Re examine incident response plans and update based on experience. Use project development and joint engineering/maintenance teams to perform early assessments of damaged infrastructure and to assess newly vulnerable areas (e.g., new erosion pa’erns due to fire impacts). Minnesota, Colorado Conduct debriefs with key stakeholders. Re examine agency conngency plans in light of event response and document lessons learned. Implement training programs for front line responders (e.g., snow plow simulator training). Arizona, D.C. Examine technology strategies that could be used to improve response efficiency (e.g., AVL monitoring of vehicle locaon). Install monitoring technology to provide alerts to maintenance staff of weather related threats (e.g., wireless connected rain gages). Install roadside traveler alert systems. Arizona, Colorado, D.C., Minnesota Examine standard operang procedures for both design and maintenance to determine if different approaches might be be’er (new design manual will be focused on risk based design and slope designs are being redefined). Vermont Expedited contract for inspecon and reconstrucon of major interchange. Hire consultants to augment staff and reduce recovery me. Understand and track the ming of a Presidenal Disaster Proclamaon; 180 day clock starts immediately. Develop electronic “as builts” that ulize survey grade accuracy LIDAR to expedite future plan development (all survey control points on a major Interstate were lost in the flood). Iowa Source: AASHTO (2013). Table II.6. (Continued). trends will enable regional agencies to improve prediction and prepare for long-term trends. • “This in turn can support the development of effective deci- sion support technology with analyses and related research on needed treatment and control approaches. • “The objective to be pursued would be road operational regimes for special extreme weather-related strategies such as evacuation, detour, closings, or limitations based on pre- programmed routines, updated with real-time information on micro weather and traffic conditions. • “For such strategies to be fully effective, improved informa- tion dissemination will be essential—both among agencies and with the public, using a variety of media. • “Finally, the institutionalization of the ability to conduct such advanced operations will depend on important changes in transportation organization and staff capacity as well as new more integrated interagency relationships.” As is seen in Table II.6, many state transportation agencies are implementing the actions suggested by Lockwood. 7.3 Summary Extreme weather events have been receiving increasing atten- tion from transportation officials for their disruptive impact on transportation system performance and more importantly

184 for their consequences to agency operations. Although trans- portation agencies have decades of experience in responding to extreme storms, recent years have seen a larger than average number of record weather events that have significantly affected transportation systems, and have placed increasing demands on transportation officials to respond quickly and efficiently. This chapter presented actions and strategies that agencies can use in event pre-planning, event management, and post-event recovery activities. Many of these strategies have been used by several agencies, while others are unique to a state and extreme weather event context (e.g., Vermont’s re-examination of design approaches for roads near rivers and streams). In all cases, however, they represent an assessment on the part of state transportation officials of what lessons can be learned from their experience with extreme weather events and how changes can be made to improve this response in future events.

185 8.1 Introduction This chapter presents the major conclusions of this research study and recommends research topics that could further cli- mate adaptation practice in the United States. The conclusions focus on the current practice of adaptation planning and likely future characteristics. The research project also produced rec- ommended practice and guidelines found in the Practitioner’s Guide (Part I of this volume) that are not repeated here. 8.2 Conclusions The climate change adaptation field is in its infancy yet con- tinues to evolve rapidly. In part caused by the occurrence of extreme weather events that surpass the damage and disrup- tion seen in prior years, but also in recognition of a growing public acceptance that climate change is an issue that needs to be considered by policy makers, new approaches and tech- niques for assessing the threats it poses are being developed. In addition, initiatives on the part of federal and state agencies to identify and demonstrate new approaches to adaptation plan- ning (e.g., the climate adaptation pilot projects sponsored by the FHWA and the FTA) have brought new tools and tech- niques to the profession. As more experience with these tools and techniques occurs, more transportation agencies can be expected to begin thinking about how climate change and extreme weather is likely to affect their operations and capital investments in the future. Overarching conclusions from this research fall into four categories: context, climate change, adaptation diagnostic framework, and agency functions. 8.2.1 Context • There is a growing understanding among researchers and highway officials that climate change and extreme weather events are a threat to many aspects of the highway system, which warrants spending resources to investigate the spe- cific risks they pose. Still, many U.S. highway agencies have not yet taken any substantive adaptation planning actions. • Both domestically and internationally, limited action has been taken “on the ground” thus far to build resiliency into the transportation system. Indeed, with some notable exceptions, much adaptation work remains at a planning or risk assessment level and has yet to be incorporated into the design of individual projects. This is likely to change in the near future as the risk assessment studies progress and as transportation officials begin to realize that in certain areas a changing climate could have significant impact on highway planning, design, construction, and operations/ maintenance. It is noteworthy that in the aftermath of Superstorm Sandy, high-level officials in New York and New Jersey called for new ways of designing infrastructure such that resiliency is built into the system. • The U.S. population will continue to grow with most of this growth occurring in urban areas and in parts of the country expecting notable changes in climate. The composition of this population will be very different than it is today, with more diverse populations and elderly in the nation’s popu- lation mix. Significant levels of housing and corresponding development will be necessary to provide places to live and work for this population, with much of this development likely to occur in areas subject to changing environmental conditions. Increasing population growth will create new demands for transportation infrastructure and services, once again in areas that are vulnerable to changing climate conditions. The nation’s highway system will be facing increasing demands for reconstruction and rehabilitation over the next 40 years (to 2050), which provides an oppor- tunity to incorporate climate adaptation strategies into such efforts, if appropriate. 8.2.2 Climate Change • Temperatures in the lower 48 states are projected to increase about 2.3°C (4.1°F) by 2050 relative to 2010. While all C H A P T E R 8 Conclusions and Suggested Research

186 U.S. regions are projected to increase in temperature, the amounts will vary by location and season. In gen- eral, areas farther inland will warm more than coastal areas, because the relatively cooler oceans will moderate the warming over coastal regions. In addition, northern areas will warm more than southern areas because there will be less high-latitude snow cover to reflect sunlight. More warming is projected for northern and interior regions in the lower 48 states than for coastal and south- ern regions. • In general, the models project and observations also show that the Northeast and Midwest are likely to become wetter while the Southwest is likely to become drier. In addition, all the climate models project an increase in precipita- tion in Alaska. It is not known whether precipitation will increase in other areas such as the Northwest or the South- east. While the models tend to show a drier Southwest and a wetter Northeast and Midwest, the differences across the models mean that forecasting exactly which localities become wetter or drier and where the transitions between wet and dry areas lie is not possible. Climate models tend to project relatively wetter winters and drier summers across most of the United States. However, this does not mean that all areas are projected to receive more precipitation in the winter and less precipitation in the summer. The mod- els also project a larger increase in summer temperature than winter temperature. • Extreme temperatures will get higher. This means that all locations will see increases in the frequency and duration of occurrence of what are now considered extreme tem- peratures such as days above 32°C (90°F) or 35°C (95°F). In the long run, the number of days below freezing will decrease in many areas, particularly southern locations. • Precipitation intensities (both daily and 5-day) are pro- jected to increase almost everywhere, although the largest increases tend to happen in more northern latitudes. • Recent research has suggested that there will be fewer hur- ricanes, but the ones that do occur, particularly the most powerful ones, will be even stronger. • Global sea levels are rising. Projections of future sea-level rise vary widely. The IPCC projects that sea level will rise 8 inches to 2 feet (0.2 to 0.6 meter) by 2100 relative to 1990. Several studies published since the IPCC Fourth Assessment Report, however, estimate that sea levels could rise 5 to 6.5 feet (1.5 to 2 meters) by 2100. Sea-level rise seen at specific coastal locations can vary considerably from place to place and from the global mean rise because of differences in ocean temperatures, salinity, and cur- rents and because of the subsidence or uplift of the coast itself. 8.2.3 Adaptation Diagnostic Framework • A diagnostic framework can be used to guide the steps in adaptation planning: Step 1: Identify key goals and performance measures for adaptation planning effort. Step 2: Define policies on assets, asset types, or locations that will receive adaptation consideration. Step 3: Identify climate changes and effects on local envi- ronmental conditions. Step 4: Identify the vulnerabilities of asset(s) to changing environmental conditions. Step 5: Conduct risk appraisal of asset(s) given vulner- abilities. Step 6: Identify adaptation options for high-risk assets and assess feasibility, cost effectiveness, and defen- sibility of options. Step 7: Coordinate agency functions for adaptation program implementation (and optionally iden- tify agency/public risk tolerance and set trigger thresholds). Step 8: Conduct site analysis or modify design standards (using engineering judgment), operating strat- egies, maintenance strategies, and construction practices. • This eight-step process is inherently a multidisciplinary and collaborative one. It is not likely that a state transportation agency has internal staff capability on climate science. In most cases, these agencies have been working with the local university or the state climatologist in order to obtain such input. In many cases, the vulnerability and risk assessment process depends on local input on what is considered to be the most critical assets in an urban area. Or, perhaps more importantly, the actions taken by local communities and governments, such as land use approval and street/drainage design, could have significant impact on the ability of state assets to handle larger loads, and thus, there is a need for coordination. • The adaptation diagnostic framework can stand alone as a separate assessment effort, or it can be aligned and/or incorporated into other agency activities (more said on this below). Some steps in the framework could provide input into such efforts as transportation planning (for example, identifying vulnerable areas or populations that need to be considered as a metropolitan area develops its improvement program or incorporating climate change–related consider- ations into project prioritization). • The lack of engineering-relevant and spatially precise climate data and the uncertainty surrounding those data remain obstacles and will likely remain so for the foreseeable future despite the best efforts of climate modelers. This should not,

187 however, be an excuse for inaction. Some governments, such as New York City, realize the data shortcomings issue and have put forth alternative approaches (e.g., flexible adapta- tion pathways) to enable prudent decision making in light of the uncertainty. This was perhaps best expressed in the Australian government’s white paper on climate change— “Uncertainty is a reason for flexibility and creativity, not for delay” (Department of Climate Change 2009). • Climate-related risk to the transportation system is one of the most important concepts in adaptation planning. Risk is broadly defined as relating to impacts beyond simply the failure of an asset. It relates to the failure of that asset in addition to the consequences or magnitudes of costs associ- ated with that failure. In this case, a consequence might be the direct replacement costs of the asset, direct and indirect costs to asset users and, even more broadly, the economic costs to society given the disruption to transportation caused by failure of the asset or even temporary loss of its services (e.g., a road is unusable when it is under water). 8.2.4 Agency Functions • Climate change adaptation can be incorporated into many functional activities of a transportation agency—planning, environmental analysis, design, infrastructure retrofit, con- struction, operations, maintenance, emergency response, and public outreach and communications. Each activity will usually require different analysis approaches, data, and resulting strategies. • It is likely that the operations and maintenance functions of a transportation agency will be the first to experience the impacts of a changing climate on a transportation sys- tem, whether this includes responding to system damage and disruption after an extreme weather event or, over the longer term, dealing with the consequences of climate changes (e.g., proliferation of new invasive species, longer mowing seasons, and less snow but more ice on the roads). • For those transportation agencies that are planning for changes and impacts that will occur due to climate change, an asset management system is well suited to help in such an effort. Given the periodic nature of infrastructure con- dition monitoring in asset management systems, combined with the maintenance efforts catalogued in maintenance management systems, these existing systems could be an important platform for incorporating climate change con- siderations into agency decision making. • Leadership is critical. Strong mandates (legislative or admin- istrative) to consider adaptation and provide relevant data greatly encourage adaptation activities. That said, they need not be a prerequisite. Absent mandates, strong state or local leadership by individuals concerned about climate change can also spur action as is the case in most U.S. examples. Vis- ible, on-the-ground changes, as in Alaska or in the aftermath of strong storms, can also focus attention on the topic. 8.3 Suggested Research The literature review conducted for this project, the ongo- ing interaction with adaptation researchers from around the world, and input from the NCHRP Project 20-83(05) panel led to a set of recommended research statements that can help define a research portfolio for advancing the state of the practice and the state of the art in adaptation research. This study identified some of the key adaptation research needs as linked to a project development life cycle. By this is meant the key activities and/or functions that are associated with taking an initial idea or need and turning it into an implemented project that will likely over time experience numerous reha- bilitation and reconstruction efforts. So, for example, this report asks, how can adaptation considerations be included in the planning process that precedes project design? How should project designs be undertaken to provide flexibility in the face of uncertainty in future environmental conditions? How should state transportation agencies look at operations and maintenance in light of extreme weather events? TRB Special Report 299: A Transportation Research Program for Mitigating and Adapting to Climate Change and Conserving Energy provided some points of departure for the research needs identified in the following paragraphs (Committee for Study on Transportation Research Programs to Address Energy and Climate Change 2009). In addition, the research team attended several international and national conferences on adaptation and has been in contact with other adaptation researchers throughout the world. Although this section does not claim to contain an exhaustive list of research needs, it does represent the current thinking on what research is needed to further adapta- tion planning in the United States. Note that this section does not describe research that is likely needed in climate science or meteorology. Because much of what transportation engineers and planners will do in adaptation clearly depends on the reli- ability and credibility of the information provided to them by the climate scientists, such information is a concern. However, to even begin to outline a research agenda for the climate sci- ence component of adaptation planning for transportation sys- tems would be well beyond the scope of this study. 8.3.1 Planning Planning constitutes those activities that lay the ground- work for individual projects, including identifying current problems in the transportation network and anticipating

188 where future problems might occur. Planning is usually data focused and relies on analysis and evaluation processes to identify the most cost-effective set of strategies that will improve transportation system performance. With respect to planning, several potential research topics deserve attention: 1. Incorporation of uncertainty into long-range transpor- tation planning: Most transportation plans have a 25- to 30-year timeframe, although a few MPOs have adopted 40- and 50-year plans. From a methodological and pro- cess perspective, how can potential climate change–related stresses be incorporated into the long-range planning process? What type of data is necessary to present cred- ible forecasts that can be used as part of the transporta- tion planning process? How can climate change scenario analyses be integrated into the traditional transportation planning process? 2. Procedures and tools for identifying vulnerable assets: Research and studies to date have generally concluded that it is beyond the scope of most planning efforts to assess every single asset in a transportation system for its vulner- ability to potential changes in climate and environmen- tal conditions. That instead, the more effective approach is to identify those assets that are the most vulnerable to environmental stressors. Vulnerability could be related to the asset location, hydrologic and soil conditions, and ter- rain characteristics. For example, an entire section of track might not be vulnerable to flooding, but a short segment over a culvert or bridge might be the weak link in the sec- tion. This segment would then become the focus of a more detailed investigation on how to protect this asset at this location. Research is needed on how to best identify vul- nerable assets in a state or region that provides the most cost-effective and strategic use of limited planning funds. 3. Procedures and tools for identifying vulnerable popu- lation groups: As was seen in recent major disasters (e.g., Hurricane Katrina), population groups are often affected differently. Those without cars, for example, are likely to be stranded unless some alterative form of transportation or protected location is provided. Research is needed that links potential climate-related environmental hazards to the location of vulnerable populations. Even more funda- mentally, research is needed on how “vulnerable popula- tions” is defined in the context of emergency evacuations or other actions related to extreme weather events. 4. Procedures and tools for identifying vulnerable net- work links: One of the adaptation characteristics inher- ent in most networks is the ability to restructure flows so as to avoid any particular location where there is a disrup- tion. Network redundancy and the ability of a network to rebound from a disruption (resiliency) is a critical aspect of a state’s or region’s resilience to natural disasters. Most every system will have critical elements of national signifi- cance that, if disrupted, may threaten this resiliency. Iden- tifying the links and nodes with the highest incremental cost would help set adaptation priorities. 5. Travel demand and mode choice: More research is needed on the effect of weather and climate on travel demand and mode choice, to separate the effects of number of trips made, mode switching, congestion avoidance, travel tim- ing, and regional climate differences. What are the expected costs associated with weather-related road delays? 6. Intercity passenger data: There is a national need for sys- tematically and periodically collecting intercity passenger data, which often do not exist at the state level and lag far behind intra-city transport data in quality and quantity. This research entails not only identifying and developing accurate data, but also strategies for embedding improved information into planning and engineering designs and improved analysis tools, specifically aimed at under- standing the implications of climate change on intercity transportation. 7. Co-benefits of adaptation strategies with other pri- orities: With limited resources to both maintain asset conditions as well as increase capacity, most state trans- portation agencies will find it difficult to implement a state-wide adaptation investment strategy. Thus, it seems likely that one element of a successful strategy will be linking adaptation actions to other investment priorities that are undertaken to achieve other goals. For example, a bridge rehabilitation and/or replacement program could include consideration of different hydrologic conditions in the future. Or land use strategies aimed at increasing densities of new development could do so in areas that are protected from increased chances of flooding. 8. Visualization tools and techniques for effective public involvement: The transportation planning process has traditionally been very open to the involvement of pub- lic groups and individuals. Over the past decade, greater attention has been given to the methods, tools, and tech- niques for visualizing the impacts of different investment strategies. What is the best way to convey to the general public the likely positive or negative impacts of different climate futures? Very little research has been conducted on how to best convey climate change–related impacts. 8.3.2 Project Development Project development includes those steps that take a project from a planning idea to final plans, specifications, and esti- mates. Thus, for example, any environmental analysis that must be undertaken to satisfy federal or state environmental requirements will occur during the project development stage,

189 as will preliminary and final engineering. Research in the fol- lowing project development areas deserves attention: 9. Environmental variable inputs into design: Improved climate data are needed at many different scales of applica- tion, especially downscaled data able to inform decisions on specific bridges, roadways, and other facilities. As noted earlier, the intent of the proposed research portfolio is not to focus so much on climate science research. However, design engineers will need to have better information on likely future environmental conditions if they are to con- sider such factors in the design process. For example, one possible strategy is to consider revised intensity, duration, and frequency (i-d-f) curves for precipitation and a strat- egy to modify runoff factors, which are used in the design of drainage systems and stormwater management facili- ties. Techniques have already been developed to derive future i-d-f curves from global climate models and they are being generated for many areas overseas and especially in Canada. The development of comparable future i-d-f curves in the United States would be of great value to engi- neers. Pavement engineers would benefit from forecasted temperature ranges to adapt current design procedures to future conditions. 10. Environmental analysis and climate change factors: How should climate change impacts be considered in the environmental analysis process? Proposed guidance from the CEQ suggests that at some point in the future environmental analyses required for projects having sig- nificant impact on the environment will include consid- eration of climate change as part of the analyses. What types of approaches can be used to do this? What data will be needed? What tools will be necessary to conduct such an analysis in a credible way? How can the results of the analyses be presented to decision makers in a way that conveys the importance of adaptation strategies? 11. Design strategies: Agencies can respond to climate change threats in a variety of ways. For example, strategies could include design for failure (simply replace the asset when it is destroyed or can no longer function), design for obso- lescence (use of shorter design lives), design for adapta- tion, design to avoid, design to protect, or no design at all (i.e., no build). Research should be conducted that looks at the advantages and disadvantages of these different strategies. Under what circumstance would a particular strategy make most sense? 12. Damage functions and cost estimates: State DOTs have many years of experience with reacting and responding to extreme weather events. To determine with any certainty what the risk is to certain types of assets, it might be use- ful to categorize the different types of damage that has been caused by different types of weather events and, for particular types of failures, to determine the range of costs that might be expected. This might require going through records of failure incidents and their costs. This informa- tion could be very useful to the conduct of risk analyses, similar to the use of depth–damage functions for assessing flooding risks for various building types. The Gulf Coast 2 project will provide such estimates for the Mobile, Ala- bama, metropolitan area, but this proposed research would provide a broader perspective on damages and costs. 13. Adaptive design processes: Similar to suggestion 11, this project would examine how, for a particular project, adap- tive design characteristics could be incorporated into proj- ect design. For example, how is project design flexibility provided for in the future when environmental conditions might change? What are examples from other infrastruc- ture areas where adaptive design capacity has been incor- porated into project design? 14. Administrative/procedural/legal barriers to adapta- tion: There are numerous examples of administrative/ procedural/legal barriers to adopting a more flexible design approach that recognizes the need for adaptive capacity. For example, some state DOT officials have suggested that there are legal issues with increasing culvert size that could lead to downstream flooding liabilities. One state DOT indicated that consideration of adaptive capacity in design concepts has been removed from consideration when the value engineering portion of the project devel- opment process looks for ways of reducing costs. This project would examine and categorize systematically the barriers that state DOTs and other transportation agen- cies might face in implementing an adaptive capacity design approach. 15. Impacts on natural resource mitigation actions: Most state DOTs have many years of experience with putting in place mitigation strategies as part of environmental agreements that come out of the project development process. For example, replacement wetlands are very common as part of project environmental agreements intended to mitigate the taking of wetlands for project construction. However, as some state DOTs have noted, these mitigation agreements often require the agencies to manage the resource in perpetuity. The research topic here is to understand the implications of changing cli- matic conditions to the function of mitigation actions that themselves could be affected by such conditions. Wetlands would be an important focus of such research. 16. Non-transportation strategies to mitigate hazardous conditions: Transportation planners and engineers usu- ally focus on transportation strategies when thinking about climate adaptation approaches. In a recent adapta- tion workshop held at the national AASHTO meeting, the Iowa DOT described how it built structures in a river

190 with highway dollars to channel flood river flow away from a downstream bridge. This project would exam- ine different non-transportation strategies that could be used to protect transportation assets. In addition, a broader perspective on the benefits of hazard protection would be examined. That is, how can such non-transpor- tation strategies provide the greatest protection not just for transportation assets, but also for communities and other critical infrastructure? 17. Off-site impacts, adaptation, and mitigation: Highway projects are not located, designed, and operated in isola- tion. The environment surrounding the highway system plays an important role in how the system operates and this off-site environment could well be affected by cli- mate change and extreme weather more so than the high- way itself. Highway agencies are not likely to build in the resilience to avoid or adapt to the impacts coming from off site. Therefore, the highway agencies must find pro- active ways to protect the highway system from off-site threats. An example would be to participate in municipal stormwater management activities to address stormwa- ter impacts upstream of the highway system. This project would identify the many off-site functions and activi- ties that could affect a highway facility, and describe the actions and strategies that highway agencies could take to mitigate the negative impact of such activities. 8.3.3 Construction, Operations, and Maintenance Weather significantly affects construction activities from high temperatures (hours of labor) and types of construc- tion materials. In addition, one of the earliest manifestations of a changing climate will occur in state DOT operations and maintenance. This manifestation includes such activities as responding to and recovering from extreme weather events and developing different operations and maintenance strate- gies for routine activities (e.g., longer growing season, more intense snow storms, etc.). The following research topics relat- ing to construction, operations, and maintenance deserve attention: 18. Construction-related impacts of weather and climate change: Changing climate and weather conditions could influence construction activities in a variety of ways. In a positive way, warmer temperatures throughout the year will lengthen the construction season in states that usu- ally curtail activities during the winter months. However, more extreme temperatures during the summer months could have negative impacts on hours of construction during mid-summer. With respect to precipitation, more intense storms could cause more erosion from construction sites and thus require greater mitigation. This project would examine the range of impacts that different climate stressors might have on construction, ranging from the physical activities involved with com- pleting a project to the use of labor on site. 19. New and weather-resistant materials and sensors for project construction: Temperature change affects in some way every component of infrastructure design because the materials used in building a structure will usually exhibit some contraction and expansion varying with the temperature. The effect of changing levels of precipita- tion would most affect foundation and pavement design, especially if precipitation levels increase significantly over today’s levels. More moisture in the soil and the hydro- static pressure build-up behind such structures as retain- ing walls and abutments might cause a rethinking of the types of materials used in construction and in dimensions such as slab thickness. Increasing storm strengths will likely be accompanied by increasing and sustained wind speeds. Greater wind speeds could require a rethinking of the support structures for traffic signs and signals. It seems likely that the advances in material sciences (with special application of nano-technologies), sensors, computer processing, and communications abilities could also have a significant impact on the way infrastructure is designed. Sensors that monitor changing pressures on a building or bridge and thus issue a warning when pressures become abnormal are already available and in limited use. “Smart” infrastructure can be envisioned that directs highly turbu- lent and fast water flows away from bridge columns and thus reduce the potential for bridge scour. Sensors could be embedded in pavements and bridge decks that moni- tor the changing stress and strain as temperatures change, allowing remedial action to be taken before complete failure occurs. Similar sensors could be applied to bridge structures in high-wind conditions to change material properties that allow the bridge to survive abnormal wind speeds. This project would examine the most challenging cli- mate stressors from the perspective of materials strength and durability. It would describe the ranges in which materials can be used without concern for failure but identify those conditions (such as prolonged heat) in which strength and durability might lessen. The project would outline specific research that would be needed to ensure that the construction materials used for long- lived transportation projects will withstand possible future conditions. In addition, it would identify promis- ing “smart” technologies that could be integrated into project design to account for weather-related factors.

191 20. Response strategies for extreme weather events: Data on extreme weather events suggest that the last several decades have seen an increase over historical patterns of such events. State DOTs have learned how to respond to such extreme events, but with the frequency and intensity of these events likely to increase, state officials need to examine how transportation agencies should prepare and respond to these changing conditions. For example, some states are pre-positioning building materials that might be necessary in the event of bridge or culvert collapses. The recent experience in Vermont with Tropical Storm Irene showed the value of having regional traffic manage- ment control centers that could direct the response and recovery activities of transportation organizations. This project would examine the different strategies states are currently adopting as well as identify others that could be undertaken. 21. Operations and maintenance activities as an early warn- ing system: Many of the climate adaptation frameworks that have been created to guide adaptation planning use threshold criteria to indicate when environmental condi- tions have reached a point where climate-related change is now sufficiently established that thought needs to be given to how state DOT activities might have to change. This project would examine how routine operations and maintenance activities could be used to provide the means by which such threshold conditions could be monitored and acted upon when reached. For example, if rock/mud- slides or road flooding have reached an occurrence rate much higher than historical records, what should the state DOT do differently in the future to protect against such events? 22. Institutional and procedural barriers to operations and maintenance strategies aimed at extreme weather events: Many rules and regulations bind what a state DOT can do with respect to operations and maintenance strategies. For example, it has been indicated that some DOTs were prohibited from removing debris from under bridges because they were unable to secure permits to remove it. The presence of the debris clearly raised the vulnerability of the bridge to flood waters. Exploring different operations and maintenance practices and environmental/institutional agreements that limit an agency’s ability to reduce risks would be an important research topic. 23. Emergency management procedures and actions: In the event of a weather-related disaster, numerous federal and state agencies become involved in providing resources for response and recovery. At the recent AASHTO work- shop mentioned earlier, several states recommended that research be undertaken on how the multiagency emergency response activity can be better streamlined and coordinated. For example, one state DOT has auto- mated the federal emergency aid submittal process such that the effort at obtaining federal emergency funding can happen much faster than before. This project would identify actions that could be taken to make emergency management procedures more efficient and effective. 8.3.4 System Management and Monitoring Ongoing management of the transportation system asset base is one of the most important functions of a state trans- portation agency. In the context of climate change, this would entail monitoring environmental conditions for any changes in environmental stresses that might result in system disrup- tion. As noted above, this can be tied into threshold criteria where once a certain threshold is reached, additional actions might be necessary. Research in the following system man- agement and monitoring areas deserve attention: 24. Use of asset management systems: Performance-based asset management is a concept that is being encouraged as part of any transportation investment program, espe- cially those supported by federal dollars (stewardship of taxpayer investment). Not only is such a concept valuable in identifying the best investment opportunities in a nor- mal investment environment, but they can become even more valuable for monitoring performance and condi- tion over time. The inventory data exists in asset manage- ment systems to allow state officials to flag those assets that need to be watched carefully in terms of vulnerabil- ity to changing environmental conditions. This research would examine how asset management systems could be used as part of a climate change–oriented system man- agement strategy. 25. Development of asset/maintenance management sys- tems for culverts: Recent experience with extreme weather events has indicated that culverts are one of the most vul- nerable components of the road network. This vulnerabil- ity has been shown to be due to not only inadequate design of the culverts themselves but also, more importantly, inadequate maintenance of the culverts. A large number of road washouts from Tropical Storm Irene in Vermont were caused by culverts that were clogged and had reduced capacity due to debris that had lodged in the culvert itself. This research would examine best practices of culvert asset management (only a few have been identified) and propose strategies for developing a culvert maintenance and design strategy for expected future extreme weather events.

192 8.3.5 Other Research into the following areas would also be beneficial: 26. Institutional Change and Capacity Building: In many ways, considering adaptation within the planning and proj- ect development context requires a very different approach to project development than what has been done previ- ously. This might require new organizational structures for dealing with climate/weather-related events and new skills and tools. In other words, transportation agencies will need opportunities for building capacity and examples of how to change institutional structures to expedite adaptation and mitigation strategies. This project would recommend capacity-building initiatives and conduct research on insti- tutional barriers to adaptive management practices and recommended solutions. 27. Clearinghouse: For transportation practitioners, a clear- inghouse of best practices in adaptive management strate- gies would provide an important resource for exchanging information as more is learned about adaptive climate change strategies. This should include highlighting a wide range of climate change adaptation strategies and in particular fostering an exchange of information on approaches for preparing for, responding to, and recov- ering from extreme weather events.

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198 The projections of temperature and precipitation changes in this research were developed using a tool called “MAGICC/ SCENGEN” (M/S; Wigley 2008). This tool contains param- eterized outputs from 20 general circulation models (GCMs). In this research, 10 models were used, which gave a wide range of projected changes in climate, particularly at the regional scale. The GCMs were the Canadian Centre for Climate Mod- eling CGCM3, the National Center for Atmospheric Research CCSM3, the Geophysical Fluid Dynamics Laboratory GFDL CM2.0 and CM2.1 (two different models), Institute Pierre Simon Laplace (France) IPSL_CM4, Center for Climate Sys- tem Research (Japan) MIROC 3.2 (medium resolution), Max Planck Institute for Meteorology (Germany) ECHAM5/MPI- OM, Meteorological Research Institute (Japan) MRI-CGCM 2.3.2, Hadley Centre for Climate Prediction and Research (United Kingdom) HadCM3 and HadGEM1. These mod- els were selected in consultation with Dr. Tom Wigley of the National Center for Atmospheric Research, the developer of M/S. He found that these 10 models best simulate the current climate of North America. While a model’s ability to simu- late current climate with fewer errors than other models does not necessarily mean that model will more reliably simulate future conditions, it does provide more faith in a model’s capabilities. Changes in temperature and precipitation are based on M/S’s estimation of climate in 2050 compared to the model’s estimation of climate in 2010; these changes are not com- pared to observed conditions. M/S is a combination of two models: MAGICC and SCENGEN. MAGICC calculates change in global mean tem- perature and sea-level rise. Users can select various factors such as greenhouse gas (GHG) emissions scenarios and cli- mate sensitivity. The latter is how much global average tem- peratures are projected to rise with a doubling of carbon dioxide levels in the atmosphere. SCENGEN divides the world into 5-degree by 5-degree grid boxes. One degree is about 60 miles long in the mid-latitudes, so each grid box is approxi- mately 300 miles across. For each GCM, SCENGEN calculates how temperature and precipitation change for each degree of change in mean global temperature. A user can select an emis- sions scenario and climate sensitivity for MAGICC, which gives an estimate of change in global mean temperature. For SCENGEN, the user can select all or some of the GCMs in the model, as well as a region of the world, and the time frame into the future for the climate projections (e.g., 2050, 2100). M/S will give regional temperature and precipitation projections for each model and will also calculate average changes across all the selected models. The parameterization scheme in M/S can also lead to a very wide range in temperature and, particularly, precipitation projections at the regional scale. The scaling of regional tem- perature and precipitation to global mean temperature can lead to very significant changes when there are large changes in global mean temperature. This happens, for example, when the high GHG emissions scenario A1FI is used and a high climate sensitivity such as 4.5°C is assumed. The results presented in this report are for all 10 of the GCMs using the A1FI emissions scenario. The “model aver- age” is the average of all 10 models. The “median” is the mean of the 5th and 6th GCMs (by rank). The 25th and 75th per- centile changes are, respectively, between the 3rd and 4th and 7th and 8th GCMs by rank. A P P E N D I X A Climate Change Modeling Platform Used for This Research

199 A P P E N D I X B Projected Climate Changes by Region

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Abbreviations and acronyms used without definitions in TRB publications: A4A Airlines for America AAAE American Association of Airport Executives AASHO American Association of State Highway Officials AASHTO American Association of State Highway and Transportation Officials ACI–NA Airports Council International–North America ACRP Airport Cooperative Research Program ADA Americans with Disabilities Act APTA American Public Transportation Association ASCE American Society of Civil Engineers ASME American Society of Mechanical Engineers ASTM American Society for Testing and Materials ATA American Trucking Associations CTAA Community Transportation Association of America CTBSSP Commercial Truck and Bus Safety Synthesis Program DHS Department of Homeland Security DOE Department of Energy EPA Environmental Protection Agency FAA Federal Aviation Administration FHWA Federal Highway Administration FMCSA Federal Motor Carrier Safety Administration FRA Federal Railroad Administration FTA Federal Transit Administration HMCRP Hazardous Materials Cooperative Research Program IEEE Institute of Electrical and Electronics Engineers ISTEA Intermodal Surface Transportation Efficiency Act of 1991 ITE Institute of Transportation Engineers MAP-21 Moving Ahead for Progress in the 21st Century Act (2012) NASA National Aeronautics and Space Administration NASAO National Association of State Aviation Officials NCFRP National Cooperative Freight Research Program NCHRP National Cooperative Highway Research Program NHTSA National Highway Traffic Safety Administration NTSB National Transportation Safety Board PHMSA Pipeline and Hazardous Materials Safety Administration RITA Research and Innovative Technology Administration SAE Society of Automotive Engineers SAFETEA-LU Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (2005) TCRP Transit Cooperative Research Program TEA-21 Transportation Equity Act for the 21st Century (1998) TRB Transportation Research Board TSA Transportation Security Administration U.S.DOT United States Department of Transportation

Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report Get This Book
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 Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report
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TRB’s National Cooperative Highway Research Program (NCHRP) Report 750: Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report provides guidance on adaptation strategies to the likely impacts of climate change through 2050 in the planning, design, construction, operation, and maintenance of infrastructure assets in the United States (and through 2100 for sea-level rise).

In addition to the practitioner’s guide and research report, this project also developed the following items:

• A software tool that runs in common web browsers and provides specific, region-based information on incorporating climate change adaptation into the planning and design of bridges, culverts, stormwater infrastructure, slopes, walls, and pavements.

• Tables that provide the same information as the previously mentioned software tool, but in a spreadsheet format that can be printed.

• Two spreadsheets that illustrate examples of the benefit-cost analysis of adaptation strategies discussed in Appendix B of Part I of NCHRP Report 750, Volume 2.

These three items are available on a CD-ROM that is included with a print version of the report. The CD-ROM is also available for download from TRB’s website as an ISO image. Links to the ISO image and instructions for burning a CD-ROM from an ISO image are provided below.

Help on Burning an .ISO CD-ROM Image.

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NCHRP Report 750, Volume 2 is the second in a series of reports being produced by NCHRP Project 20-83: Long-Range Strategic Issues Facing the Transportation Industry. Major trends affecting the future of the United States and the world will dramatically reshape transportation priorities and needs. The American Association of State Highway and Transportation Officials (AASHTO) established the NCHRP Project 20-83 research series to examine global and domestic long-range strategic issues and their implications for state departments of transportation (DOTs); AASHTO's aim for the research series is to help prepare the DOTs for the challenges and benefits created by these trends.

Other volumes in this series currently available include:

• NCHRP Report 750: Strategic Issues Facing Transportation, Volume 1: Scenario Planning for Freight Transportation Infrastructure Investment

• NCHRP Report 750: Strategic Issues Facing Transportation, Volume 3: Expediting Future Technologies for Enhancing Transportation System Performance

• NCHRP Report 750: Strategic Issues Facing Transportation, Volume 4: Sustainability as an Organizing Principle for Transportation Agencies

• NCHRP Report 750: Strategic Issues Facing Transportation, Volume 5: Preparing State Transportation Agencies for an Uncertain Energy Future

• NCHRP Report 750: Strategic Issues Facing Transportation, Volume 6: The Effects of Socio-Demographics on Future Travel Demand

CD-ROM Disclaimer - This software is offered as is, without warranty or promise of support of any kind either expressed or implied. Under no circumstance will the National Academy of Sciences or the Transportation Research Board (collectively "TRB") be liable for any loss or damage caused by the installation or operation of this product. TRB makes no representation or warranty of any kind, expressed or implied, in fact or in law, including without limitation, the warranty of merchantability or the warranty of fitness for a particular purpose, and shall not in any case be liable for any consequential or special damages.

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