Development of a national-scale fluvial flood exposure dataset for the conterminous United States, Alaska, and Hawaiʻi

Abstract

Flooding on military installations can threaten mission-essential functions and critical DOD assets. Identification of flood occurrence and future change is therefore needed to anticipate and mitigate adverse consequences. To meet this need, the DOD Extreme Conditions Assessment Tool (DECAT) provides the military departments with web-based, data-driven assessments of exposure to inland flooding, among other types of extreme weather. Prior DECAT versions have relied on maps with limited spatial coverage (i.e., within installation boundaries) and assumed uniform increases in future flood conditions. The latest version of DECAT (version 6.0, released 30 September 2025) seeks to enable exposure assessments beyond installation boundaries and incorporate additional flood-mapping methodologies. This report documents the development of a new national-scale flood map dataset that covers the entire United States and uses twenty-first century hydroclimate projections to capture potential changes in flood exposure. The dataset was generated using the AutoRAPID modeling system, which couples a continental-scale river routing tool to a raster-based flood mapping tool. An evaluation of model output reveals a tendency to underestimate conditions associated with flooding, meaning more conservative, higher-fidelity estimates of flood exposure may still be needed to adequately capture flood risk, especially where required by applicable laws and standards.