Integrating Urban Expansion and Flood Risk: A Spatial Assessment of Impervious Surface Growth and Floodplain Exposure in Mecklenburg County (2011–2021)
Pegah Madadi, Azad Sadeghi
Abstract
ABSTRACT Urban expansion significantly impacts flood risk, particularly in rapidly growing areas where impervious surfaces exacerbate surface runoff. This study examines spatial patterns of urban growth and their effects on flood exposure in Mecklenburg County, North Carolina, from 2011 to 2021. Using impervious surface data and spatial statistical models, we analyze the extent, pattern, and risks linked to urban development within FEMA‐designated 500‐year floodplains. Results show that average impervious surface coverage rose from 28.6% to 35.9% across block groups, with 32.1% of new development happening within flood‐prone areas. A combined flood risk index (FRI), combining standardized impervious growth and floodplain area, identified 15 high‐risk block groups. Spatial analysis methods, including Global Moran's I, local indicators of spatial association (LISA), geographically weighted regression (GWR), and Getis‐Ord Gi* hotspot mapping, confirmed significant spatial clustering of development and risk. Additionally, comparisons between the spatial error model (SEM) and the spatial lag model (SAR) showed spatial dependence in urban expansion, with the SEM providing a slightly better fit. Predictive modeling with SAR and generalized additive models (GAM) identified areas of future development pressure and nonlinear relationships between distance to floodplains and impervious growth. These findings underscore the importance of spatially informed urban planning and proactive flood mitigation in rapidly growing regions. This comprehensive geospatial framework provides a transferable model for assessing development pressures in hydrologically sensitive landscapes nationwide.