Characteristics of urban waterlogging induced by spatiotemporal variations of typhoon rainfall in a coastal city

To investigate the impact of spatiotemporal variations in typhoon-induced rainfall on the processes of urban waterlogging in coastal cities of China, a numerical model of surface water dynamics and its associated transport processes was applied. The central business district of Ningbo, a coastal city in China, was selected as the study area. The scope of this research encompassed a comprehensive examination of urban waterlogging under various scenarios, including conditions featuring both moving typhoon-induced rainfall and stationary typhoon-induced rainfall. The findings of this study are as follows : ① Rainfall moving in different directions leads to a delayed accumulation of water at waterlogging monitoring sites. The delay ranges from 0 to 0.5 hours when the rainfall moves directly westward or northwestward, 1.5 hours when moving directly northward, and 1.5 to 2 hours when moving in a direction 30 degrees east of north. ② In 92% of the simulated scenarios, the movement of rainfall results in a reduction in both the volume and depth of water accumulation. The maximum reduction rate of peak water depth reaches 4.46%. As the return period of rainfall increases from 5 a to 50 a, the reduction rate of peak water depth decreases from 0.49% to 0.10%. ③ The impact patterns of bimodal and unimodal rainfall on urban waterlogging are similar, but the former has a comparatively lesser impact. Therefore, in cities affected by typhoon-induced rainfall, the disaster prevention and mitigation ministry should give special consideration to the spatiotemporal movement characteristics of the typhoon-induced rainfall. This approach is crucial for further enhancing urban flood resilience and mitigating disaster losses.