Using Flood Insurance Claims in Coastal CONUS to Evaluate the Impact of Compound Flood Risk

Abstract Compound coastal flooding, resulting from the coincidence of river flood and storm surge, often leads to more severe consequences than either driver alone. With climate change, the frequency and impact of such events are expected to become more frequent and damaging, particularly in rapidly developing coastal areas. In the U.S., the National Flood Insurance Program (NFIP) administered by the Federal Emergency Management Agency (FEMA), has recorded more than 2 million claims since 1978, yet few studies have examined these claims in the context of compound flooding. This study analyzes NFIP claims data from over 60,000 coastal counties to evaluate economic losses from riverine, coastal, and compound flood (CF) events. We attribute causes of flood using a topography‐driven indicator, D‐Index (Mitu et al., 2023, https://doi.org/10.1016/j.jhydrol.2023.130278 ), and compare claim frequencies across coastal, river, and compound zones. We also assess how rainfall and tide characteristics influence claims in compound events and compare high‐risk FEMA flood zones with lower‐risk areas. Across the U.S. coastal regions, counties prone to CF events are associated with higher payouts than counties mostly affected by single flood drivers. Additionally, we find that nearly 50% of coastal counties experience flood damage and claims outside FEMA's Special Flood Hazard Area (SFHA). Our analysis also shows that SFHA underrepresent CF risk for 22%–40% of the counties located in different regions of the coastal U.S. Through this proposed framework, our study offers a robust foundation for improving coastal flood risk assessment to help coastal communities better manage risks associated with compound flooding events.