Flood Hazard Maps for Local Flood Policy in the United States: Barriers and Opportunities

Problem, research strategy, and findings Although limitations of U.S. Federal Emergency Management Agency (FEMA) flood maps are well documented, important gaps remain in our understanding of: (1) How do flood map coverage, detail, and currency vary across communities? (2) Where are these regulatory maps contested? We assembled a novel data set of 5,938 map amendment records in Virginia spanning 1998 to 2021 and combined it with spatial analysis and statistical models. Our results show that only 28% of rivers have mapped floodplains, and just over half of these floodplains include detailed boundary and elevation information. Flood maps average 10 years in age, with some older than 28 years. Map coverage, detail, and currency vary widely across locations, with clear disparities between urban and rural areas, and between coastal and inland communities. Our results also show that contestations to floodplain designation occur more frequently in lower-density areas of population centers—consistent with development pressures in urban fringes—and are more common in lower-income and higher-minority neighborhoods, suggesting heightened sensitivity to the financial and regulatory burdens of floodplain designation. In addition, map contestations are more likely in areas where local physical conditions increase uncertainty in flood mapping.Takeaway for practice Federal and state agencies should prioritize expanding flood map coverage and detailed studies, particularly in underserved rural and inland areas, and place greater emphasis on nonregulatory maps. These products can provide more timely and comprehensive flood information, improve equitable information access, and support more proactive and flexible local flood policies. Recognizing where flood maps are often contested, local governments should use these interactions to strengthen risk communication and identify unmet mitigation needs. This includes targeted outreach, mitigation assistance, and insurance support in vulnerable and fast-growing neighborhoods, as well as adopting locally defined flood zones that supplement FEMA designations to better manage areas facing different levels of flood hazard.