Flood risk redistribution due to gaps and constraints in adaptation strategies

Levees are critical adaptation measures for mitigating the escalating flood risks posed by intensifying climatic extremes and rapid urban expansion into flood-prone areas. However, the implementation of these measures is often constrained by administrative boundaries and financial limitations, which confine adaptation efforts to predefined jurisdictions. These constraints result in adaptation gaps that disproportionately affect communities beyond protected zones and exacerbate inequalities in flood risk distribution. Our study integrates hydrodynamic and economic modeling to evaluate the magnitude, spatial distribution, and economic losses associated with levee-based flood protection strategies in Surat, a coastal city frequently exposed to severe riverine flooding. The findings indicate that levees designed to safeguard administrative boundaries can inadvertently intensify flood risks for unprotected communities and infrastructure by altering hydrodynamic conditions. Specifically, 100-year flood damages and extents increase significantly due to levee-induced changes. Our preliminary results highlight the spatially widespread nature of flood impacts, unaccounted costs, and the potential for increased socioeconomic inequities. These findings emphasize the need for a systems-based approach to flood management that considers the interconnectedness of river systems and promotes equitable sharing of flood risks across jurisdictions.