Flood risk investigation of pedestrians and vehicles in a mountainous city using a coupled coastal ocean and stormwater management model

To examine the attributes, underlying mechanisms, and impacts of rainfall patterns on the vulnerability of pedestrians and vehicles to flood-induced instability within mountainous urban areas, we introduced an integrated urban flood model that combined the Storm Water Management Model (SWMM) and Finite Volume Coastal Ocean Model (FVCOM). We implemented this model in the Yuelai New Town of Chongqing, China. Our findings indicated that in the case of early peak rainfalls, there was a rapid surge in flood volume during the initial stages of rainfall , while this increase was more gradual when the peak rainfall was delayed. Furthermore, for events with the same return period, flood peaks resulting from later peak rainfalls covered a larger area compared with those from earlier peak rainfalls; however, this effect diminished with increasing return periods. As the return period was extended, the exposed risk area for pedestrians and vehicles expanded. Analysis of instability indices revealed that pedestrians exhibit a lower index compared with vehicles, adults fare better than children, and SUVs outperform sedans. The efficacy of our proposed model framework was demonstrated through its successful application in assessing urban flood risk and evaluating the instability index for pedestrians and vehicles within a mountainous urban setting.