Urban sprawl drives heterogeneous flood exposure patterns along socio-demographic gradients: a case study in the Amite River Basin during the 2016 Louisiana (USA) Floods

Abstract The impact of floods may be exacerbated due to urban sprawl, which leads to residential development in naturally flood-prone areas. In the United States (US), urban sprawl has been historically tied to racial segregation, while flood-prone suburban development has been facilitated by flood insurance. While previous studies have found links between flood exposure and socio-demographic inequities, no research has addressed this question by looking at watershed-level segregation and the location of properties relative to flood-prone areas. We evaluate socio-demographic patterns of flood impact during the 2016 Floods in Louisiana (LA), USA, and whether these impacts differed inside or outside the FEMA Special Flood Hazard Area (SFHA), the nation’s main flood risk indicator for property owners. We assess this question in the Amite River Basin (ARB), LA, looking at the following socio-demographic predictors: (1) race, (2) income, (3) year of property built, and (4) property type, and accounting for the location of properties relative to the FEMA-SFHA (inside/outside), and the Parish of origin. The FEMA SFHA was generally a good predictor of flood impact, and the most impacted parishes were those within the downstream area of the ARB (EBR-East Baton Rouge, Ascension, and Livingston). At the watershed scale, properties in blocks dominated by wealthier black residents had a greater impact during this flood event, but the trends, varied by parish. Trends in the older and more urban EBR parish reflected those reported for the watershed. In the newer suburban parishes of Ascension and Livingston, the highest impact was experienced by high-income, predominantly white neighborhoods, mainly inside the FEMA SFHA. Properties built between 1970–1989 were associated with higher flood impact than homes built during other periods. While socio-demographic predictors of flood exposure were heterogeneous across the ARB, our findings collectively highlight the social costs of suburbanization into hazardous areas.