Modeling urban planning contributions to flood resilience under shared socioeconomic pathways

Abstract Flooding from short-duration extreme rainfall poses growing risks to rapidly urbanizing regions under climate change. This study integrates 2035 urban planning into simulations of extreme rainfall-induced flooding in the Pearl River Delta Metropolitan region. Results show that while urban planning has limited impact on reducing overall hazard, it plays a critical role in redistributing it spatially. Flood hazard and exposure in 2035 were assessed under four Shared Socioeconomic Pathways (SSPs). Hazard decreases by about 10% in SSP1, remains stable in SSP2, and rises in SSP3 and SSP5, with SSP5 showing a 12% increase. Population exposure grows across all scenarios, with increases of 21% in SSP1, 25% in SSP2, 13% in SSP3, and 56% in SSP5. Asset exposure shows even larger increases, from 29% in SSP3 to more than 100% in SSP5. These results highlight that while urban planning can alleviate hazard locally, long-term resilience is dominated by socioeconomic development trajectories.