An exploratory framework for flood risk assessment considering cascade effect of inundation volume in highly developed urban areas

Due to the escalating effects of global climate change and the rapid pace of urban development, urban flooding events are occurring more frequently, causing considerable economic losses and far-reaching social consequences. Evaluating flood risk is essential for effective urban flood management and the development of disaster reduction strategies. This study adopts a tracer-aided urban flood model to distinguish endogenous and exogenous flood volume, and establishes an exploratory framework for flood risk assessment considering cascade effect of inundation volume. The Haikou City's Haidian Island in Hainan Province, China was selected as the study area. Eight risk assessment indicators were chosen, and a combined weighting method that integrated the analytic hierarchy process with the entropy weight method was used to determine their individual weights. A spatial map depicting flood risk throughout the study area was created using the model's outputs. The spatial differentiation law of endogenous and exogenous flood risks was revealed. Furthermore, Comparative simulations of flood mitigation schemes demonstrated that the source-oriented regulation guided by the proposed framework delivers better flood mitigation performance. This study provides targeted technical support for refined urban flood risk management.