Spatiotemporal analysis of residential flood exposure in the Atlanta, Georgia metropolitan area

This research examines changes in residential built-environment flood exposure within the current boundaries of the Atlanta, Georgia metropolitan statistical area, by estimating the number of housing units that are located within the floodplains of the region. Housing unit data at the block level from the 1990 to 2010 decennial censuses are used to estimate housing unit exposure to floods using a binary dasymetric and proportional allocation method. Three different representations of the 100-year (1 percent annual chance) and 500-year (0.2 percent annual chance) floodplain are employed: the generally more conservative floodplains created using the Federal Emergency Management Agency’s Hazus-MH software, the generally more extensive floodplains included in the proprietary Flood Hazard Data product from KatRisk LLC and the regulatory floodplains from the National Flood Insurance Program. The number of housing units within both the 100- and 500-year floodplain increased from 1990 to 2010 throughout the Atlanta region. Housing unit growth within the regulatory 100-year flood zone was slower than growth elsewhere, suggesting that the National Flood Insurance Program may have been marginally effective overall. Results using the KatRisk product reveal both greater overall and a greater increase in housing units at risk within the 100-year floodplain than the regulatory product suggests. The results argue that heightened flood exposure, particularly in areas experiencing new development, is an important factor to consider when addressing the impact of the flood hazard over time.