Deciphering spatial-temporal dynamics of flood exposure in the United States,

Abstract

Extracting baseline information on flood exposure and its temporal evolution is essential to formulate flood risk reduction strategies. At present, comprehensive, long-term spatial-temporal flood exposure research in the United States is lacking. The objective of the study is to evaluate county-wide flood exposure in the US and unravel its spatial-temporal dynamics from 2001 to 2019 to answer three research questions via hypothesis testing. First, how have human settlement areas exposed to flood threats in the US changed over the past two decades? Second, has the occurrence of floods and their resulting damage influenced the growth of developed areas in flood zones? Third, do disparities exist in the sensitivity to flood threats among urban-rural communities? Results show that the overall rate of development in flood zones in the contiguous United States has steadily decreased from 2001 to 2019. The Local Moran's I analysis discovers pockets of emerging, expanding, shrinking, and changing 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 demonstrate greater responsiveness to flood hazards by avoiding development in flood zones. Finally, urban communities exhibit a higher exposure and sensitivity to flood hazards compared to rural areas.