Incorporating the Costs and Benefits of Adaptation Measures in Preparation for Extreme Weather Events and Climate Change—Guidebook (2020) / Chapter Skim
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Pages 21-36
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21 Models and Scenarios Climate science has made significant advancements in the past couple of decades in the ability to model complex interactions occurring between dynamic factors. Global models, called general circulation models (GCMs)
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22 Incorporating the Costs and Benefits of Adaptation Measures in Preparation for Extreme Weather Events and Climate Change -- Guidebook Box 2. (Continued)
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Climate Considerations 23 Figure 7. CMIP5 CO2 emissions scenarios (van Vuuren et al., 2011)
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24 Incorporating the Costs and Benefits of Adaptation Measures in Preparation for Extreme Weather Events and Climate Change -- Guidebook Climate scientists use multiple consensus-based scenarios illustrating a spectrum of modeled changes in climate and weather over the 21st century, so selecting the appropriate climate scenarios is necessary to arrive at a useful CBA (Figure 9)
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Climate Considerations 25 Non-probabilistic scenarios allow planners to ask questions based in probabilistic climate projections without relying on a specific SRES or RCP so that they can better manage risk. Planners can then focus on the risk issues at stake rather than bring in climate change and the path under way.
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26 Incorporating the Costs and Benefits of Adaptation Measures in Preparation for Extreme Weather Events and Climate Change -- Guidebook FHWA has undertaken research to evaluate non-stationarity and associated potential impacts on transportation infrastructure, in particular through its Gulf Coast studies and climate- resilience pilot studies. These studies have enabled FHWA to identify different asset types' sensitivities to various climate stressors.
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Climate Considerations 27 Paved Roads Culverts Bridges Buildings Extreme Heat Sustained high temperatures can soften asphalt concrete pavement, resulting in rutting and shoving. Concrete pavement can heave at the joints.
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Paved Roads Culverts Bridges Buildings Sea Level Change Hydraulically, sea level rise will reduce the 100-year return periods of floodcausing events because static water levels will be higher, so less rainfall and runoff will be required to achieve the same 100year flood elevation (i.e., a smaller event will cause the same 100-year flooding)
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Climate Considerations 29 Paved Roads Culverts Bridges Buildings Wind Wind does not directly damage pavements, but can disrupt traffic. Debris generated from a wind event can clog the stormwater drainage system, resulting in localized flooding.
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30 Incorporating the Costs and Benefits of Adaptation Measures in Preparation for Extreme Weather Events and Climate Change -- Guidebook Paved Roads Culverts Bridges Buildings Changes in Freeze/ Thaw Pavement reaction to freeze/thaw cycles depends on the paving mix (e.g., aggregate, air voids)
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Topic Design or Regulatory Considerations Example Guidance FEMA Floodplain Practical alternatives to locating within the floodplain for the 100-year event Increases in the 100-year water surface elevation of an established regulatory floodway Increases in the water surface outside the regulatory floodplain (less than 1.0 ft) and impact on additional property Backwater limitations Title 23, Section 650, Subpart A: Location and Hydraulic Design of Encroachments on Flood Plains of the Code of Federal Regulations FHWA Non-Regulatory Supplement Attachment 2 Local jurisdiction drainage design criteria (e.g., Virginia DOT Drainage Design Manual)
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32 Incorporating the Costs and Benefits of Adaptation Measures in Preparation for Extreme Weather Events and Climate Change -- Guidebook Topic Design or Regulatory Considerations Example Guidance Erosion and Sediment Control Flow depth Flow direction Velocity Discharge Width Presence of debris Use of geotextiles Landscaping and slope planting Temporary measures during construction AASHTO Guide for Transportation Landscape and Environmental Design Department of Environmental Quality Erosion and Sediment Control Handbook Local jurisdiction guidelines and standards Overtopping Assumes weir flow Velocity Head (elevation of overtopping water minus road-surface elevation) Flood frequency at which overtopping occurs FHWA (2016)
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Climate Considerations 33 Figure 12. A decision tree can help inform decisions about whether to adapt to climate change and extreme weather.
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34 Incorporating the Costs and Benefits of Adaptation Measures in Preparation for Extreme Weather Events and Climate Change -- Guidebook • Do the scenarios agree, or mostly agree, on the direction of those changes (i.e., all show either an increase or a decrease)
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Climate Considerations 35 Figure 13. Decision makers need to determine if they want to remain on a business-as-usual path or want to pursue other policies (USGCRP, Figure 2.7, 2017)
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36 Incorporating the Costs and Benefits of Adaptation Measures in Preparation for Extreme Weather Events and Climate Change -- Guidebook and adjusted to be statistically consistent with their corresponding recurrence intervals. Discharges for future conditions were found to be higher than those for current conditions, so future discharges were used in the design calculations for the new structure.
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