SURFLI: mapping social and flood vulnerabilities across urban–rural low-income/low-access areas in North Carolina

Flooding is a persistent hazard in the southeastern U.S., with particularly severe consequences for socially vulnerable populations, especially those in low-income, low-access (LILA) communities. This study introduces a GIS-based framework to explore the intersection of social vulnerability, flood exposure, and LILA conditions across urban and rural areas in North Carolina. Using data from the U.S. Census, the American Community Survey, the EPA floodplain maps, and USDA LILA metrics, we identify significant spatial disparities in flood risk and infrastructure access. The Brunner‒Munzel and Spearman statistics highlight substantial differences in socio-economic vulnerability and flood risk between urban and rural regions, as well as between LILA and non-LILA communities. Regression models, including ordinary least squares and multiscale geographically weighted regression (MGWR), reveal how social vulnerability varies spatially and impacts local areas differently. A key contribution of this study is integrating a principal component analysis (PCA) derived from the social vulnerability index (SVI) into the MGWR model. The resulting Social, Urban‒Rural, Flood, and LILA vulnerability Index (SURFLI) combines social, environmental, and infrastructural factors to assess vulnerability across different geographic scales. Hotspot analysis identifies distinct composite vulnerability zones. SURFLI provides a scalable tool for supporting floodplain management and promoting equitable access planning in flood-prone regions.