Flash Flood Risk Assessment in the context of Economic Change Scenarios

Flash flood disasters pose a constant threat to socioeconomic factors in southeastern China. This study analyzes the risk change of flash floods in the Yantanxi River Basin, southeastern China, under five economic scenarios (SSP1, SSP2, SSP3, SSP4 and SSP5). We built a regional flash flood hazard assessment model by combining hydrological and hydrodynamic models with field work. Asset value was used to represent regional exposure, which was spatialized using data from industrial structure and land use. Flash flood risk assessment influenced by economic change was developed using different industry responses to flash floods. The results clarify how economic factors drive flash flood risk changes. The return period of the 2019 flash flood in the Yantanxi River Basin is 150-year. In 2019, flash floods affected 5.04% of the river basin; the inundation depth was concentrated at under 2.00 m, resulting in CNY 0.55 billion in economic damage. With economic change, the flash flood risk increases by 91.34% (SSP2- current economic development level) and 94.39% (SSP5-extreme economic development level). This study emphasizes the balance between economic development and disaster management at the river basin scale; additionally, our method provides a reference for risk assessment in flash-flood prone areas lacking statistical information.