Multiscalar Assessment of Flood Zone Occupation and Environmental Justice: A Case Study of the Charlanta Megaregion

Urban areas are particularly vulnerable to flood hazards due to impervious surfaces altering the runoff response as well as socio-economic pressures increasing the number of individuals residing in areas at risk for flooding. Although previous studies have utilized an environmental justice framework to address the socio-economic dimensions of this vulnerability, they have produced contrasting results due to the different dasymetric mapping techniques utilized to estimate urban flood zone population characteristics, the various scales at which the estimates are calculated, and the specific geographical context of the individual study cities. This paper aims to evaluate the sensitivity of potential environmental injustices regarding urban flood risk to these parameters by analyzing flood zone occupancy with three different dasymetric mapping techniques at four scales for numerous metropolitan areas within the Charlanta megaregion. Specifically, 2010 US Census block group data, FEMA flood zones, and risk ratios were used to evaluate if African Americans were overrepresented in areas at risk for flooding. Although the results varied according to the different dasymetric mapping techniques, the most sophisticated approach suggested that environmental injustices were systemic across the megaregion, as African Americans were 44% more likely to reside in areas at risk for flooding than Whites. Similarly, at the metropolitan scale, African Americans were significantly more likely to reside in flood zones. A more complex and spatially varying landscape of inequitable exposures was observed at the county and census tract scales. However, the overall systemic nature of flood zone environmental justice issues observed across Charlanta suggests that broad structural changes will be required to ultimately reduce the disproportionate flood risk that African Americans bear.