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

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128 When conducting cost-benefit analyses (CBAs), analysts may base estimates of losses avoided from future events on similar, past events. They may know when the event occurred and how much damage transportation infrastructure sustained as a result of the event, but they may not know the recurrence interval of the event. Unknown recurrence interval calculators are tools that can help to estimate the recurrence interval of an event so that a CBA can be completed. FEMA Damage Frequency Analysis Module FEMA’s Benefit-Cost Analysis software includes a Damage Frequency Analysis (DFA) module that allows the user to calculate project costs and benefits when the analyst does not have accu- rate or complete hazard or structural information. The FEMA DFA is relatively flexible; it can be used for a variety of hazard and project types and can be based on either historic or expected damages data. When using the Unknown Recurrence Interval (RI) calculator in the DFA to conduct an analysis using historic data, the user must have data for at least three events, and one of these events must have a known RI. When using the Unknown RI calculator in the DFA to conduct an analysis using expected damages data, the user must have at least one event, and all events used must have a known RI. Additional information about the FEMA DFA module is available from FEMA’s BCA website: https://www.fema.gov/media-library/assets/documents/18878. The FEMA BCA tool is a SQL server–based tool. FTA Hazard Mitigation Cost-Effectiveness Tool The FTA Hazard Mitigation Cost-Effectiveness (HMCE) tool uses a methodology similar to the FEMA DFA’s Unknown RI approach to calculate unknown recurrence intervals. Similar requirements apply regarding the number and type of events (i.e., known versus unknown RIs) required to complete an analysis. The FTA HMCE tool is freely downloadable from the FTA Emergency Relief Program website and is an Excel-based spreadsheet tool rather than a SQL server–based tool (https://www.transit.dot.gov/funding/grant-programs/emergency-relief- program/hazard-mitigation-cost-effectiveness-tool). It was developed specifically for transit projects, but was designed to apply to a wider range of transportation projects. A P P E N D I X F Unknown Recurrence Interval Calculator Tools