Incorporating the Costs and Benefits of Adaptation Measures in Preparation for Extreme Weather Events and Climate Change—Guidebook (2020)

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2020 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 RESEARCH REPORT 938 Incorporating the Costs and Benefits of Adaptation Measures in Preparation for Extreme Weather Events and Climate Change—Guidebook Dewberry engineers inc. Fairfax, VA Venner consulting, inc. Denver, CO impact infrastructure, inc. Toronto, ON mcVoy associates llc Slingerlands, NY Subscriber Categories Design • Economics • Environment Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration 15465-00b_FM-3rdPgs.indd 1 6/5/20 12:52 PM

NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Systematic, well-designed, and implementable research is the most effective way to solve many problems facing state departments of transportation (DOTs) administrators and engineers. Often, highway problems are of local or regional interest and can best be studied by state DOTs individually or in cooperation with their state universities and others. However, the accelerating growth of highway transporta- tion results in increasingly complex problems of wide interest to high- way authorities. These problems are best studied through a coordinated program of cooperative research. Recognizing this need, the leadership of the American Association of State Highway and Transportation Officials (AASHTO) in 1962 ini- tiated an objective national highway research program using modern scientific techniques—the National Cooperative Highway Research Program (NCHRP). NCHRP is supported on a continuing basis by funds from participating member states of AASHTO and receives the full cooperation and support of the Federal Highway Administration (FHWA), United States Department of Transportation, under Agree- ment No. 693JJ31950003. The Transportation Research Board (TRB) of the National Academies of Sciences, Engineering, and Medicine was requested by AASHTO to administer the research program because of TRB’s recognized objectivity and understanding of modern research practices. 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Published research 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 by going to https://www.nationalacademies.org and then searching for TRB Printed in the United States of America NCHRP RESEARCH REPORT 938 Project 20-101 ISSN 2572-3766 (Print) ISSN 2572-3774 (Online) ISBN 978-0-309-48159-5 Library of Congress Control Number 2020938331 © 2020 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, FTA, GHSA, NHTSA, or TDC 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 research 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 National Academies of Sciences, Engineering, and Medicine. 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 Academies of Sciences, Engineering, and Medicine; the FHWA; or the program sponsors. The Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; 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.

The National Academy of Sciences was established in 1863 by an Act of Congress, signed by President Lincoln, as a private, non- governmental institution to advise the nation on issues related to science and technology. Members are elected by their peers for outstanding contributions to research. Dr. Marcia McNutt is president. The National Academy of Engineering was established in 1964 under the charter of the National Academy of Sciences to bring the practices of engineering to advising the nation. Members are elected by their peers for extraordinary contributions to engineering. Dr. John L. Anderson is president. The National Academy of Medicine (formerly the Institute of Medicine) was established in 1970 under the charter of the National Academy of Sciences to advise the nation on medical and health issues. Members are elected by their peers for distinguished contributions to medicine and health. Dr. Victor J. Dzau is president. The three Academies work together as the National Academies of Sciences, Engineering, and Medicine to provide independent, objective analysis and advice to the nation and conduct other activities to solve complex problems and inform public policy decisions. The National Academies also encourage education and research, recognize outstanding contributions to knowledge, and increase public understanding in matters of science, engineering, and medicine. Learn more about the National Academies of Sciences, Engineering, and Medicine at www.nationalacademies.org. The Transportation Research Board is one of seven major programs of the National Academies of Sciences, Engineering, and Medicine. The mission of the Transportation Research Board is to provide leadership in transportation improvements and innovation through trusted, timely, impartial, and evidence-based information exchange, research, and advice regarding all modes of transportation. The Board’s varied activities annually engage about 8,000 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 individuals interested in the development of transportation. Learn more about the Transportation Research Board at www.TRB.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 RESEARCH REPORT 938 Christopher J. Hedges, Director, Cooperative Research Programs Lori L. Sundstrom, Deputy Director, Cooperative Research Programs Stephan A. Parker, Senior Program Officer Stephanie L. Campbell, Senior Program Assistant Eileen P. Delaney, Director of Publications Natalie Barnes, Associate Director of Publications NCHRP PROJECT 20-101 PANEL Field of Special Projects Charles C. Fielder, Arcata, CA (Chair) Debra A. Nelson, New York Metropolitan Transportation Council, New York, NY Chris Baglin, DSA, Inc., McLean, VA Todd Donald Carlson, Washington State DOT, Burlington, WA Cris B. Liban, Los Angeles County Metropolitan Transportation Authority, Los Angeles, CA Lezlie Rupert, Union Station Redevelopment Corporation, Washington, DC Ann M. Scholz, New Hampshire DOT, Concord, NH Elizabeth Shay, Appalachian State University, Boone, NC Dan Tran, University of Kansas, Lawrence, KS Robert Kafalenos, FHWA Liaison Rawlings Miller, FMCSA Liaison Matthew H. Hardy, AASHTO Liaison William B. Anderson, TRB Liaison

This report provides an overview of the current state of the practice on the use of cost- benefit analysis (CBA) in the decision-making process within transportation agencies, identifies how CBA can be incorporated into transportation-planning processes along with climate adaptation, and develops two frameworks for evaluating the potential cost- effectiveness of incorporating climate adaptation measures into projects. This report has the potential to serve as • A single resource that summarizes the current state of the practice for incorporating CBA into adaptation planning and analysis; • A source for identifying existing, relevant data and tools to support CBA for adaptation planning; and • An intuitive guide for incorporating CBA into state and local transportation asset management and planning policies and procedures that incorporate climate change and extreme weather adaptation planning. Extreme weather events and a changing climate can result in significant costs to trans- por tation agencies, to the traveling public, and to communities. State departments of transportation (DOTs) as well as other public infrastructure agencies are increasingly challenged with difficult decisions about whether, when, and to what extent to incorporate adaptation measures into their existing and future facilities to provide more resilience in the event of extreme weather or in response to the evolving effects of climate change. Given the potential costs and benefits involved in enhancing the resilience of transportation systems, the decision to implement adaptation measures is dependent on a variety of factors. Improved guidance will assist transportation decision makers in making informed and supportable decisions regarding implementation of adaptation measures for extreme weather events and climate change. The return on investment will be realized from making better long-term decisions based on a more holistic analysis of the costs and benefits of implementing adaptation measures. Under NCHRP Project 20-101, “Guidelines to Incorporate the Costs and Benefits of Adaptation Measures in Preparation for Extreme Weather Events and Climate Change,” a research team led by Dewberry Engineers developed a methodology and handbook for practitioners to use in conducting a simple CBA by hand or with a spreadsheet to eval- uate the most cost-effective climate and extreme weather adaptation and response. The team began with a literature review, conducted a survey of current practices at state DOTs around the country, and followed up with in-depth telephone interviews of practitioners. The team’s aim was to gain a broad understanding of the tools, methods, data, and models used by practitioners; their decision-making processes; and perceived needs. A gap analysis F O R E W O R D By Stephan A. Parker Staff Officer Transportation Research Board

informed a recommended framework and architecture to organize existing tools, methods, and data for practitioner use and built on existing resources based on the needs identified in the gap analysis. The framework and architecture considered both capital cost components and non-capital cost components such as environmental impacts. This research produced additional resources (available on the TRB website at http://www. trb.org/Main/Blurbs/180405.aspx), including a PowerPoint presentation that describes the research and the results; a spreadsheet tool that provides an approximate test to see if it would be cost-effective to upgrade assets to the future conditions posed by climate change; a second spreadsheet tool that (1) uses existing conditions without climate change only to calculate the new return period for future conditions with climate change and (2) also calculates a benefit-cost ratio that can be used by decision makers to evaluate whether an adaptation project would be a worthwhile investment. The contractor’s final report that describes the methodologies used is provided on the TRB website as NCHRP Web-Only Document 271 at http://www.trb.org/main/blurbs/180536.aspx.

1 Summary 3 Chapter 1 Introduction 3 Synopsis of Issue 4 Target Audience 4 Why Was the Guidebook Developed? 4 How Was the Guidebook Prepared? 4 What Specifically Does the Guidebook Provide? 6 Chapter 2 Cost-Benefit Analysis Overview 6 Introduction 7 Cost-Benefit Analysis Definition and Use 8 Steps in Conducting a Cost-Benefit Analysis 10 Cost-Benefit Analysis Metrics 14 Different Types of Cost-Benefit Analysis 15 Funding Sources and Their Impact on Analysis 21 Chapter 3 Climate Considerations 21 Models and Scenarios 25 Considering Changing Climate in a Proposed Design 32 Evaluating If Adaptation Is Needed When Guidelines Are Not Available 34 Incorporating Climate Change into Cost-Benefit Analysis 37 Chapter 4 Common Costs 37 Financial Costs 39 Environmental and Social Costs 41 Chapter 5 Common Benefits 41 Losses Avoided 47 Environmental Benefits 50 Social Benefits 52 Safety 53 Economic Impact Analysis versus Cost-Benefit Analysis 55 Chapter 6 Conducting a Cost-Benefit Analysis 55 Appropriate Level of Analysis 56 Selection of Alternatives and Analysis Time Frame 60 Recurrence Intervals 63 Base and Alternative Cases 68 Chapter 7 Study Level 1 Climate Resilience Cost-Benefit Analysis 68 Introduction to Levels of Analysis 71 Process Walk-Through with an Example for Riverine Flooding 79 Case Study 85 Application of Study Level 1 Analysis to Sea Level Rise C O N T E N T S

88 Chapter 8 Study Level 2 Climate Resilience Cost-Benefit Analysis 88 Introduction to Study Level 2 Analysis 88 Process Walk-Through with an Example 95 Case Study 101 Study Level 2 Analysis with Sea Level Rise 103 Conclusion 105 Appendix A Discount Rate Information 112 Appendix B Present Value Interest Factor Table 113 Appendix C Climate Information, Design Guidelines, and Data Sources 125 Appendix D Cost Worksheet 126 Appendix E Cost-Estimating Tools 128 Appendix F Unknown Recurrence Interval Calculator Tools 129 Appendix G Worksheet for Level 1 Analysis 141 Appendix H Worksheet for Level 2 Analysis 153 Appendix I Blank Level 1 Worksheet 162 Appendix J Cost-Benefit Analysis Data Sources 165 Appendix K Cost-Benefit Analysis Tools 174 Appendix L Existing Frameworks Related to the Cost-Benefit Analysis Process 175 Bibliography 181 Acronyms Note: Photographs, figures, and tables in this report may 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.