Incorporating the Costs and Benefits of Adaptation Measures in Preparation for Extreme Weather Events and Climate Change (NCHRP Report 938)
This guidebook, Incorporating the Costs and Benefits of Adaptation Measures in Preparation for Extreme Weather Events and Climate Change (Guidebook), provides a comprehensive resource to help transportation agencies incorporate cost-benefit analysis (CBA) into planning processes and decisions regarding needs for adapting to climate change and extreme weather. The Guidebook was published in 2020 and developed through the National Cooperative Highway Research Program, with input from practitioners at state departments of transportation (DOTs).
The Guidebook was developed to help fill a gap in the tools and resources readily available to state DOTs to help them make decisions about how to address climate risks to infrastructure assets. CBA can be a powerful tool to help DOTs evaluate potential adaptation options with a long-term view that considers likely climate change impacts over the lifetime of an asset. However, despite the existence of some tools and resources to help with climate-informed CBA, many state DOTs still experienced barriers to using CBA, such as lack of capacity or time to complete. The Guidebook helps to address these barriers by providing a consolidated resource to help practitioners more readily consider CBA in their decisionmaking processes relating to adaptation options, providing a needed link between the well-established process of assessing vulnerabilities, and adaptation implementation.
The Guidebook provides an overview of the current state of practice on incorporating CBA into adaptation decisions in the transportation sector, identifies sources of data and tools to assist with CBA, and includes a guide on incorporating CBA into transportation asset management and planning for climate change and extreme weather. This includes:
- An overview of different types of CBA, metrics (e.g., net present value), and the effect that funding sources can have on CBA (Chapter 2);
- An overview of climate change considerations that affect CBA, including selection of scenarios and timeframes, and information on how to account for non-stationarity (Chapter 3);
- Analysis of common costs and benefits (e.g., losses avoided and other environmental and social benefits) that are included in CBA, including environmental and social considerations that may be included in more in-depth CBA (triple-bottom line) (Chapters 4 and 5);
- Information on how to select appropriate alternatives for a CBA and integrating into planning processes (see, e.g., figure below) (Chapter 6);
- A new approach to facilitate tiered CBA that will help agencies first estimate whether adaptation measures would be cost-effective before conducting a more in-depth CBA (Chapters 7 and 8);
- Additional information on different discount rates, climate change models and information, guidelines, and data sources; cost estimating tools; other tools for assisting agencies in dealing with uncertainty; data sources and tools for CBA; and worksheets for completing cost estimates and different levels of CBA analysis (Appendices).
Notably, the new CBA approach illustrated in Chapters 7 and 8 helps to address practitioner concerns about the time and resource constraints of conducting CBA, especially for lower-budget projects. The "Level 1" analysis allows practitioners to approximate whether adaptation measures should be incorporated, which can be used as an initial screening tool. The "Level 2" analysis is an approach that returns a full benefit-cost ratio and net present value of costs and benefits under future conditions. The Guidebook illustrates these levels of analysis using case studies.
The Guidebook was developed following a multi-step process involving literature review, outreach to state DOTs, and gap analysis. Outreach included a survey administered to state DOTs on how they are currently assessing costs and benefits of adaptation measures, followed by detailed phone interviews with practitioners to further elaborate on the tools and methods in use, and perceived needs. The gap analysis informed the development of a framework for using existing tools, methods, and data. The research effort also produced spreadsheet tools to help decisionmakers evaluate the cost effectiveness of adaptation projects. The project was funded through the National Cooperative Highway Research Program, administered by the Transportation Research Board of the National Academies of Sciences, Engineering, and Medicine.
Publication Date: 2020
- Assessment guide