Development patterns and climate change are contributing to increasing flood risk across the United States. Limiting development in floodplains mitigates risk by reducing the assets and population exposed to flooding. Here, we develop two indexes measuring floodplain development for 18,548 communities across the continental United States. We combine land use, impervious surface, and housing data with regulatory flood maps to determine what proportion of new development has taken place in the floodplain. Nationwide from 2001 to 2019, 2.1 million acres of floodplain land were developed, and 844,000 residential properties were built in the floodplain. However, contrary to conventional perceptions of rampant floodplain development, just 26% of communities nationwide have developed in floodplains more than would be expected given the hazard they face. The indexes and the analyses they enable can help guide targeted interventions to improve flood risk management, to explore underlying drivers of flood exposure, and to inform how local‐to‐federal policy choices can be leveraged to limit hazardous development.
Plain Language Summary Development in areas prone to flooding increases flood risk by increasing the exposure of people and infrastructure. Reducing or limiting development in hazardous areas can be a critical way for communities to manage flood risk. In this study, we use national flood hazard, impervious surface, and housing data sets to create two indexes measuring the extent of floodplain development across the United States from 2001 to 2019. Surprisingly, we find that despite seemingly large aggregate numbers, most communities have actually limited hazardous development when we account for how much of their developable land is in the floodplain. We show that floodplain development outcomes vary across key influences, including geography, wealth, and flood risk management efforts. Our indexes enable comparisons across community contexts, potentially unlocking important lessons for effective floodplain management. Proactive, climate‐smart land use planning will be key to ensuring resilient growth for communities moving forward.
Key Points Substantial development took place in floodplains across the US from 2001 to 2019 but less than expected given the extent of flood hazards Floodplain development outcomes vary across a number of key factors, including geography, socioeconomics, and flood risk management Nationwide indexes capturing local outcomes enable evaluation of floodplain management policies and drivers of floodplain developmen
