Exploring characteristics and drivers of flood hazard under different urban development patterns

Urban expansion can influence flooding by altering impervious area, surface runoff and the distribution of population. While the impact of urban development on flood hazards has been widely studied, the variation in flood characteristics in the context of urban development patterns remain insufficiently explored. This study analyzed flood characteristics and driving factors across 49 study units within the Pearl River Basin from 1998 to 2022. Using the VIC and CaMa-Flood models, we simulated river flood depth and captured inundation map. Nearly 2 % of built-up area suffer flood inundation, and by comparing inundated area without flood protection, there is around 88 % reduction in inundated area with 100-year flood protection level. Urban development patterns were identified by population and built-up area, then study units were grouped into four distinct types combined effects of flood hazard levels and urban development: (i) expanding units with hazard-improved, (ii) expanding units with hazard-unimproved, (iii) non-expanding units with hazard-improved, and (iv) non-expanding units with hazard-unimproved. Four driving factors are identified by Kolmogorov-Smirnov tests, including vegetation coverage, elevation, distance to nearest drainage and soil permeability, which significantly influence flood hazard. This study presents a novel framework for assessing flood hazards by integrating urban development heterogeneity. Results would contribute to future urban planning and enhancing flood resilience.