Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report (2014)

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N A T I O N A L C O O P E R A T I V E H I G H W A Y R E S E A R C H P R O G R A M NCHRP REPORT 750 Strategic Issues Facing Transportation Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report Michael Meyer Michael Flood Jake Keller Justin Lennon Gary McVoy Chris Dorney Parsons Brinckerhoff Washington, DC Ken Leonard Robert Hyman camBridge systematics Cambridge, MA Joel Smith stratus consulting Boulder, CO Subscriber Categories Design • Highways • Planning and Forecasting TRANSPORTAT ION RESEARCH BOARD WASHINGTON, D.C. 2014 www.TRB.org Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration

NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Systematic, well-designed research provides the most effective approach to the solution of many problems facing highway administrators and engineers. Often, highway problems are of local interest and can best be studied by highway departments individually or in cooperation with their state universities and others. However, the accelerating growth of highway transportation develops increasingly complex problems of wide interest to highway authorities. These problems are best studied through a coordinated program of cooperative research. In recognition of these needs, the highway administrators of the American Association of State Highway and Transportation Officials initiated in 1962 an objective national highway research program employing modern scientific techniques. This program is supported on a continuing basis by funds from participating member states of the Association and it receives the full cooperation and support of the Federal Highway Administration, United States Department of Transportation. The Transportation Research Board of the National Academies was requested by the Association to administer the research program because of the Board’s recognized objectivity and understanding of modern research practices. The Board is uniquely suited for this purpose as it maintains an extensive committee structure from which authorities on any highway transportation subject may be drawn; it possesses avenues of communications and cooperation with federal, state and local governmental agencies, universities, and industry; its relationship to the National Research Council is an insurance of objectivity; it maintains a full-time research correlation staff of specialists in highway transportation matters to bring the findings of research directly to those who are in a position to use them. The program is developed on the basis of research needs identified by chief administrators of the highway and transportation departments and by committees of AASHTO. Each year, specific areas of research needs to be included in the program are proposed to the National Research Council and the Board by the American Association of State Highway and Transportation Officials. Research projects to fulfill these needs are defined by the Board, and qualified research agencies are selected from those that have submitted proposals. Administration and surveillance of research contracts are the responsibilities of the National Research Council and the Transportation Research Board. The needs for highway research are many, and the National Cooperative Highway Research Program can make significant contributions to the solution of highway transportation problems of mutual concern to many responsible groups. The program, however, is intended to complement rather than to substitute for or duplicate other highway research programs. Published reports of the NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM are available from: Transportation Research Board Business Office 500 Fifth Street, NW Washington, DC 20001 and can be ordered through the Internet at: http://www.national-academies.org/trb/bookstore Printed in the United States of America NCHRP REPORT 750, VOLUME 2 Project 20-83(5) ISSN 0077-5614 ISBN 978-0-309-28378-6 Library of Congress Control Number 2013932452 © 2014 National Academy of Sciences. All rights reserved. COPYRIGHT INFORMATION Authors herein are responsible for the authenticity of their materials and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used herein. Cooperative Research Programs (CRP) grants permission to reproduce material in this publication for classroom and not-for-profit purposes. Permission is given with the understanding that none of the material will be used to imply TRB, AASHTO, FAA, FHWA, FMCSA, FTA, or Transit Development Corporation endorsement of a particular product, method, or practice. It is expected that those reproducing the material in this document for educational and not-for-profit uses will give appropriate acknowledgment of the source of any reprinted or reproduced material. For other uses of the material, request permission from CRP. NOTICE The project that is the subject of this report was a part of the National Cooperative Highway Research Program, conducted by the Transportation Research Board with the approval of the Governing Board of the National Research Council. The members of the technical panel selected to monitor this project and to review this report were chosen for their special competencies and with regard for appropriate balance. The report was reviewed by the technical panel and accepted for publication according to procedures established and overseen by the Transportation Research Board and approved by the Governing Board of the National Research Council. The opinions and conclusions expressed or implied in this report are those of the researchers who performed the research and are not necessarily those of the Transportation Research Board, the National Research Council, or the program sponsors. The Transportation Research Board of the National Academies, the National Research Council, and the sponsors of the National Cooperative Highway Research Program do not endorse products or manufacturers. Trade or manufacturers’ names appear herein solely because they are considered essential to the object of the report. Front cover, image used in third circle from the top: © Washington State Department of Transportation. Used under Creative Commons license (CC BY-NC-ND 2.0).

The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. On the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Ralph J. Cicerone is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. C. D. Mote, Jr., is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, on its own initiative, to identify issues of medical care, research, and education. Dr. Harvey V. Fineberg is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy’s purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Ralph J. Cicerone and Dr. C. D. Mote, Jr., are chair and vice chair, respectively, of the National Research Council. The Transportation Research Board is one of six major divisions of the National Research Council. The mission of the Transporta- tion Research Board is to provide leadership in transportation innovation and progress through research and information exchange, conducted within a setting that is objective, interdisciplinary, and multimodal. The Board’s varied activities annually engage about 7,000 engineers, scientists, and other transportation researchers and practitioners from the public and private sectors and academia, all of whom contribute their expertise in the public interest. The program is supported by state transportation departments, federal agencies including the component administrations of the U.S. Department of Transportation, and other organizations and individu- als interested in the development of transportation. www.TRB.org www.national-academies.org

C O O P E R A T I V E R E S E A R C H P R O G R A M S CRP STAFF FOR NCHRP REPORT 750, VOLUME 2 Christopher W. Jenks, Director, Cooperative Research Programs Crawford F. Jencks, Deputy Director, Cooperative Research Programs Edward T. Harrigan, Senior Program Officer Anthony P. Avery, Senior Program Assistant Eileen P. Delaney, Director of Publications Natalie Barnes, Senior Editor NCHRP PROJECT 20-83(5) PANEL Area of Special Projects Randell H. Iwasaki, Contra Costa Transportation Authority, Walnut Creek, CA (Chair) Anne Criss, Soquel, CA Stephen W. Fuller, Texas A&M University, College Station, TX Wayne W. Kober, Wayne W. Kober Transportation & Environmental Management Consulting, Dillsburg, PA Sue McNeil, University of Delaware, Newark, DE Arthur C. Miller, State College, PA J. Rolf Olsen, U.S. Army Corps of Engineers, Alexandria, VA Harold R. Paul, Louisiana DOTD, Baton Rouge, LA John V. Thomas, U.S. Environmental Protection Agency, Washington, DC Michael Culp, FHWA Liaison J. B. Wlaschin, FHWA Liaison Thomas R. Menzies, TRB Liaison

F O R E W O R D 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 established the NCHRP Project 20-83 research series to exam- ine global and domestic long-range strategic issues and their implications for departments of transportation (DOTs) to help prepare the DOTs for the challenges and benefits cre- ated by these trends. NCHRP Report 750: Strategic Issues Facing Transportation, Volume 2: Climate Change, Extreme Weather Events, and the Highway System: Practitioner’s Guide and Research Report is the second report in this series. This report presents guidance on adaptation strategies to likely impacts of climate change through 2050 in the planning, design, construction, operation, and maintenance of infra- structure assets in the United States (and through 2100 for sea-level rise). There are many potential impacts of climate change on the highway system. Climate change is likely to increase the Earth’s average temperature, change extreme temperatures in different parts of the world, raise sea levels, and alter precipitation patterns and the inci- dence and severity of storms. Such change will likely become an important driver of how the state departments of transportation (DOTs) design, plan, construct, operate, and maintain their highway systems. Recent extreme weather events, such as Hurricanes Katrina and Sandy, and massive flooding in the Northwest and Midwest states, have led to a rethinking of how infrastructure is designed and managed during such events. Practitioners need a sound foundation on which to plan for the near-term—through 2050—impacts of climate change. This foundation should encompass an assessment of the probable impacts, identification of vulnerable infrastructure, and technical tools and proposed institutional arrangements to guide adaptation of the infrastructure to the antici- pated impacts. The objectives of NCHRP Project 20-83(05) were to (1) synthesize the current state of worldwide knowledge regarding the probable range of impacts of climate change on high- way systems by region of the United States for the period 2030–2050; (2) recommend insti- tutional arrangements, tools, approaches, and strategies that state DOTs can use to adapt infrastructure and operations to these impacts and lessen their effects; and (3) identify future research and activities needed to close gaps in current knowledge and implement effective adaptive management. The research was conducted by Parsons Brinckerhoff (Washington, D.C.) in association with Cambridge Systematics (Cambridge, Massachusetts) and Stratus Consulting (Boulder, Colorado). By Edward T. Harrigan Staff Officer Transportation Research Board

The project examined adaptation to climate change on three scales of application—road segment, corridor, and network—including the types of impacts likely to be faced in coming years and the different design, operations, and maintenance strategies that can be consid- ered. The report discusses adaptation planning in the United States and in other countries, with special consideration for the approaches taken in developing adaptation strategies. A diagnostic framework for adaptation assessment is presented consisting of eight steps: 1. Identify key goals and performance measures for the adaptation planning effort. 2. Define policies on assets, asset types, or locations that will receive adaptation consideration. 3. Identify climate changes and effects on local environmental conditions. 4. Identify the vulnerabilities of asset(s) to changing environmental conditions. 5. Conduct risk appraisal of asset(s) given vulnerabilities. 6. Identify adaptation options for high-risk assets and assess feasibility, cost effectiveness, and defensibility of options. 7. Coordinate agency functions for adaptation program implementation (and optionally identify agency/public risk tolerance and set trigger thresholds). 8. Conduct site analysis or modify design standards (using engineering judgment), operat- ing strategies, maintenance strategies, and construction practices. This volume assembles two major project deliverables: • The Practitioner’s Guide (Part I) to conducting adaptation planning from the present through 2050 (through 2100 for sea-level rise) • The research report (Part II) that summarizes the research results supporting the devel- opment of the Practitioner’s Guide and provides recommendations for future research. Three other project deliverables are available on the accompanying CD-ROM and on the TRB website (http://www.trb.org/Main/Blurbs/169781.aspx): • 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 strat- egies discussed in Appendix B of Part I.

C O N T E N T S P A R T I Practitioner’s Guide 3 Summary 10 Chapter 1 Introduction and Purpose 10 Why Is This Guide Needed? 11 What Is Adaptation? 12 Who Should Read What? 14 Chapter 2 Framework for Adaptation Planning and Strategy Identification 14 What Are the Steps for Adaptation Planning? 22 What Is the Relationship between Climate Change and Transportation Planning? 25 How Does the Framework Fit into the Organization of the Guide? 27 Chapter 3 Projected Changes in the Climate 27 What Do Climate Models Do? 28 What Are Emission Scenarios? 30 What Is Climate Sensitivity? 31 Can Regional Climate Be Modeled? 32 What Will the Climate Be Like in 2050? 37 What about Sea-Level Rise? 38 Where Are Climate Data and Advice Available for a Specific State? 39 What Needs to be Known about Climate Forecasting with Models? 42 Chapter 4 Possible Impacts to the Highway System and the Natural Environment and Agency Responses to Them 42 How Could Changes in Temperature Affect Road Assets? 44 How Could Changes in Precipitation Affect Road Assets? 46 How Could Sea-Level Rise Affect Road Assets? 47 How Could Greater Hurricane Intensity Affect Road Assets? 47 How Could Climate Stressors Affect Ecological Systems? 50 What Are the Types of Adaptation Strategies that Can Be Considered by Transportation Agencies? 53 Summary 56 Chapter 5 Vulnerability Assessments and Risk Appraisals for Climate Adaptation 56 What Is the Difference between Vulnerability and Risk? 59 Why Consider Climate-Related Risk? 59 What If Probabilities Are Not Available?

61 How Can the Results of Risk Assessment Be Portrayed without Probabilities? 66 What If Probabilities Are Available or Could Be Developed? 68 How Can Climate Change Scenarios Be Used to Account for Uncertainty in Decision Making? 70 Summary 71 Chapter 6 Climate Change and Project Development 71 How Can Climate Adaptation Be Considered in Environmental Analysis? 73 How Is Engineering Design Adapted to Constantly Changing Climate? 85 Summary 86 Chapter 7 Other Agency Functions and Activities 86 How Could Climate Change and Extreme Weather Events Affect Construction? 87 How Could Climate Change and Extreme Weather Events Affect Operations and Maintenance? 91 What Role Can Asset Management Play in an Agency’s Climate Adaptation Activities? 93 How Should Coordination with Other Organizations and Groups Work When Considering Adaptation Strategies? 96 References 101 Appendix A Sea-Level Rise Projections 103 Appendix B Benefit–Cost Methodology for Climate Adaptation Strategies P A R T I I Research Report 117 Summary 121 Chapter 1 Introduction and Research Objectives 121 1.1 Introduction 122 1.2 Problem Statement and Research Objectives 122 1.3 Study Scope and Research Approach 124 Chapter 2 Research Approach and Conceptual Framework of the Highway System 124 2.1 Introduction 124 2.2 Research Approach 124 2.3 Conceptual Framework of the Highway System 131 2.4 Summary 132 Chapter 3 Current Practice in Adaptation Planning and Adaptive Management 132 3.1 Introduction 132 3.2 U.S. Perspectives 141 3.3 International Perspectives 145 3.4 Diagnostic Framework 148 Chapter 4 Context for Adaptation Assessment 148 4.1 Introduction 148 4.2 Potential Demographic, Land Use, and Transportation System Changes in the United States by 2050

150 4.3 Expected Changes in Climate 158 4.4 Summary 159 Chapter 5 Potential Impacts on the U.S. Road System 159 5.1 Introduction 159 5.2 Climate Change Impacts on the Highway Network 166 5.3 Climate Impact to Ecological Conditions 166 5.4 Adaptation Strategies 171 5.5 Summary 173 Chapter 6 A Focus on Risk 173 6.1 Introduction 173 6.2 Risk Assessment Defined 175 6.3 Approaches to Risk Assessment 179 6.4 Summary 181 Chapter 7 Extreme Weather Events 181 7.1 Introduction 181 7.2 Extreme Weather Events and Transportation Agency Operations 183 7.3 Summary 185 Chapter 8 Conclusions and Suggested Research 185 8.1 Introduction 185 8.2 Conclusions 187 8.3 Suggested Research 193 References 198 Appendix A Climate Change Modeling Platform Used for This Research 199 Appendix B Projected Climate Changes by Region Note: Many of the photographs, figures, and tables in this report have been converted from color to grayscale for printing. The electronic version of the report (posted on the Web at www.trb.org) retains the color versions.