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Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2020. Incorporating the Costs and Benefits of Adaptation Measures in Preparation for Extreme Weather Events and Climate Change—Guidebook. Washington, DC: The National Academies Press. doi: 10.17226/25744.
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Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2020. Incorporating the Costs and Benefits of Adaptation Measures in Preparation for Extreme Weather Events and Climate Change—Guidebook. Washington, DC: The National Academies Press. doi: 10.17226/25744.
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Suggested Citation:"Chapter 1 - Introduction." National Academies of Sciences, Engineering, and Medicine. 2020. Incorporating the Costs and Benefits of Adaptation Measures in Preparation for Extreme Weather Events and Climate Change—Guidebook. Washington, DC: The National Academies Press. doi: 10.17226/25744.
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3 Synopsis of Issue Extreme weather events and a changing climate increasingly boost costs to transportation agencies and to the traveling public. The World Meteorological Association reports that the world is nearly five times as prone to weather-related disasters now as it was in the 1970s. This change in the frequency and severity of extreme weather events in the United States has already increased travel delays (10 to 24 percent) and crash risks (by 24 percent on slick pavement or in adverse weather). Extreme weather events also reduce traffic speed and roadway capacity, disrupting access. Fifteen percent of all road congestion is due to bad weather and 25 percent is due to incidents, costing the United States over $9.45 billion per year just in major urban areas. Weather-related delays add $3.4 billion to freight costs annually. Altogether, the societal cost of adverse weather in terms of crashes, fatalities, injuries, and property damage through 2055 is estimated to be $23.074 trillion (Guevara, 2013). In recent years, state DOTs have begun to understand that the organization and availability of their personnel and equipment are as critical to their agencies as the performance of the physical infrastructure system and the short-term budget and system restoration priorities. For example, the 2010 Tennessee floods, a 1,000-year event, required 83,000 state DOT maintenance hours to deal with damage in 41 counties. Damage included sinkholes up to 25 feet wide and deep that developed 2 weeks after the initial floods, closing Interstate 40 (Transportation Research Circular E-C152, 2011). Increasing storm damage and flooding have a significant adverse impact on DOT operating budgets, which are absorbing costs for more risk communication to the public, road repairs related to heat buckling, or more extensive problems caused by extreme storms and floodwaters to roads, road bases, bridges, and culverts. As states have begun to experience the impacts of the increasing frequency of extreme weather events on their systems, many state DOTs have started to evaluate factors such as criticality, traveler delays, economic impacts on freight, emergency management needs, and safety, and to include these factors when evaluating the implications of climate change on their systems and the cost-effectiveness of possible improvements. For example, the Washington State DOT studied one 4-day closure and estimated $18 million in damages to state highways, as well as freight-related economic impacts of $47 million in lost economic output, $2 million in lost state tax revenues, and $14 million in lost personal income (Ivanov et al., 2008). To make the best use of limited resources and achieve the best results possible in the face of extreme weather, state DOTs need to understand what data and tools are available to help them make informed, timely decisions by weighing the benefits and costs of different feasible courses of action given the situational constraints. Cost-benefit analysis (CBA), also referred to as benefit- cost analysis (BCA), is one tool decision makers can use to evaluate if and how to incorporate climate change adaptation or extreme weather into the design of a transportation asset or system. C H A P T E R 1 Introduction

4 Incorporating the Costs and Benefits of Adaptation Measures in Preparation for Extreme Weather Events and Climate Change—Guidebook Target Audience This guidebook is intended to assist an audience with varying levels of knowledge and expe- rience with CBA and climate adaptation related to transportation assets. For those with little knowledge or experience working with CBA, the guidebook provides background information about what these analyses are and why they are conducted, different types of CBAs, factors that contribute to the development of a CBA, and how results might be interpreted using differ- ent metrics. For those with little knowledge of climate change, the guidebook provides some background information about the most commonly used climate models and how they can be applied in the context of a CBA. For those with more experience, the guidebook provides infor- mation about how a climate-informed CBA could be conducted and provides examples of how to incorporate climate predictions into CBAs. Why Was the Guidebook Developed? State DOTs and other public infrastructure agencies are increasingly challenged with difficult decisions about whether, when, and to what extent to incorporate adaptation measures into existing and future facilities to provide more resilience in the event of extreme weather or in response to the evolving effects of climate change. NCHRP has developed guidance that enables transportation decision makers to integrate analysis of the costs and benefits of adapta- tion measures in preparation for extreme weather events and climate change. Such rigorous analysis will benefit practitioners making planning and funding decisions in a fiscally constrained environment. How Was the Guidebook Prepared? The authors of this guidebook conducted an extensive literature review that considered existing research; tools, methods, and data for traditional cost-benefit analysis frameworks; hazard miti- gation frameworks; transportation capital planning and investment frameworks; operations, emergency response, and recovery-planning frameworks; and climate-resilience frameworks. The authors also considered recent federal-level transportation policy and funding drivers and their potential impacts on policies and goals at the state and local agency levels. In addition to conducting desktop reviews, the research team disseminated a survey to DOTs regarding their current use of CBA and their experience with resilience planning for climate adaptation and extreme weather events. The team supplemented the information received from the survey by conducting interviews with DOT personnel to further understand their experiences, challenges, and successes with resilience planning and use of CBA as a decision support tool. The guidebook summarizes these findings and uses them as a practical basis to provide a clear picture of the issues and to facilitate development of frameworks to address these challenges. The frameworks the research team developed maintain consistency with existing guidance from federal agencies such as the FHWA and the Federal Emergency Management Agency (FEMA), with the idea that these approaches may be most familiar to users. The frameworks were also developed so that CBAs could be completed by hand if necessary, provided the needed data inputs are available. Required data inputs can be obtained or calculated from existing, often readily available, data sets and tools. What Specifically Does the Guidebook Provide? This guidebook provides a summary and an explanation of the information needed to complete CBAs at varying levels of analysis. It explains the key parameters included in any CBA, as well as different types of CBAs, the data required for each type of analysis, and potential data sources.

Introduction 5 It allows users to evaluate whether climate or extreme weather adaptation measures are viable at the asset or corridor levels from a financial or triple bottom-line perspective and, if so, the allowable value of the measures that could be implemented to maintain a positive net present value for the project. Chapters 2 through 5 of this guidebook provide educational background information about the components of CBA, climate considerations, and common costs and benefits and how they are quantitatively and qualitatively evaluated. This guidebook uses a fictitious scenario to illus- trate the various principles involved with completing a CBA. The scenario was developed based on the assumption that a DOT has already completed a risk analysis of assets and corridors as part of its transportation asset management process. People experienced with CBA or interested in getting straight into conducting a climate- informed CBA might elect to skip Chapters 2 through 5 and go straight to Chapter 6. The Scenario A road in Chesterfield County, Virginia, has been identified during the asset management risk analysis as being a critical facility to the local transportation network. Hydraulic structures that support the road are scheduled for replace- ment, and the Virginia DOT is trying to determine if certain adaptation measures should be incorporated into the designs for the replacement structure. Are such measures needed to accommodate additional risk associated with increased flows from extreme weather or climate risks that could lead to flooding and wash out the road? The current metal culvert is designed to withstand a flood event that has a return period of 50 years, which corresponds to a flow of 9,000 cubic feet per second. A cost-benefit analysis will be conducted for the current culvert as well as for the adaptation options being considered, and will be used in the decision-making process. Data gathering for the analysis is commencing. Data needed at this stage include • Facility of concern, • Geographic location of the facility or corridor under consideration, • Hazards of concern, and • Current design criteria: – Flow rate (or other parameter of interest) for the hazard of interest design event and – Recurrence interval for the hazard of interest design event.

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Extreme weather events and a changing climate increasingly boost costs to transportation agencies and to the traveling public. While Departments of Transportation (DOTs) are taking into account changing climate and extreme weather when making infrastructure decisions, they typically are not using a formal set of tools or cost-benefit analyses (CBAs) to address climate resilience because they may be too time-consuming and expensive to conduct routinely.

The TRB National Cooperative Highway Research Program's NCHRP Research Report 938: Incorporating the Costs and Benefits of Adaptation Measures in Preparation for Extreme Weather Events and Climate Change—Guidebook was developed to try to fill the gaps identified by DOTs. It is intended to provide a consolidated resource for transportation practitioners to be able to more readily consider CBAs as a tool in their investment-decision making processes when considering different climate and extreme weather adaptation alternatives.

This report has additional resources, including a web-only document NCHRP Web-Only Document 271: Guidelines to Incorporate the Costs andBenefits of Adaptation Measures in Preparation for Extreme Weather Events and Climate Change, a Power Point 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, and a spreadsheet tool that uses existing conditions without climate change only to calculate the new return period for future conditions with climate change.

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