Federally-overlooked flood risk inequities in the conterminous United States

Climate change is exacerbating flood risks globally. In the U.S., Federal Emergency Management Agency (FEMA) Flood Insurance Rate Maps (FIRMs) delineate areas at high flood risk (i.e., 100-year floodplains), however, FIRMs are incomplete and outdated. We utilize risk estimates from advanced flood modeling and sociodemographic data at the census tract level to examine inequities in risk to federally-overlooked 100-year flooding across the conterminous United States (CONUS). Using multivariable statistics that account for clustering and non-normality, we analyze inequities by flood type (coastal, pluvial, and fluvial) and along the urban-rural continuum. Results indicate that 26 million CONUS residents live in federally-overlooked 100-year floodplains. Lower income is associated with elevated risk of federally-overlooked 100-year flooding for all flood types across the urban-rural continuum. We find inconsistent relationships for neighborhood racial/ethnic composition, yet increased Black composition is associated with greater risk of federally-overlooked 100-year pluvial flooding in metropolitan areas, where 47% of the CONUS population at risk to federally-overlooked flooding resides. In suburban and rural contexts, higher Hispanic/Latinx composition is associated with increased risk of federally-overlooked fluvial flooding. The large scale and inequities of federally-overlooked flood risk we find have major public policy, planning and environmental justice implications that demand flood resilience interventions.