Deciphering the Dynamics of Flood Risks: A Comprehensive Geospatial and Temporal Assessment in the Contiguous United States

Abstract

Extracting baseline information on flood risk and its temporal evolution is essential to formulating flood risk reduction strategies. At present, there is a lack of comprehensive, long-term spatial-temporal flood risk research in the United States. The objective of the study is to evaluate county-wide flood risk in the US and unravel its spatial-temporal dynamics from 2001–2019 to answer four research questions via hypothesis testing. First, what proportions of the population and developed areas are at risk of 100-year and 500-year floods? Second, how has flood risk in the US changed over time? Third, how does communities' sensitivity to flooding risk vary based on flood occurrences and damages? Fourth, do disparities in sensitivity to flood risk exist between urban and rural communities? The U.S. FEMA 100-year and 500-year flood map dataset, Microsoft building footprint dataset, census data, land cover data, SHELDUS flood frequency, and damages data were used. Results show that the overall rate of development in flood zones in the contiguous United States has steadily decreased from 2001–2019. The Local Moran’s I analysis discovers pockets of clusters of communities that show a rapid increase or decrease of developed areas within flood zones over time. Most counties that experienced more frequent flooding events demonstrated greater responsiveness to flood hazards by avoiding development in flood zones. Finally, urban communities exhibit higher exposure and sensitivity to flood hazards compared to rural areas. The findings of the study provide essential baseline information for policymakers and disaster practitioners to design flood mitigation policies and strategies.