Simulation of urban flood using the SWMM with the hierarchical catchment partition method

In order to effectively improve the accuracy of urban rainstorm flood simulations, the catchment hierarchical partition based on the spatial information method and the determination method of stormwater inlets were proposed in this study, owing to the complicated urban underlying surfaces and the absence of stormwater inlets. Taking the Qingshan district of Wuhan City as a study area, the SWMM model was calibrated and verified for the two typical rainfall hydrographs. Different simulated results were obtained by the validated SWMM model, with the results using different sub-catchment division methods being compared with the actual waterlogging data. The results indicate that: ① The determination method of stormwater inlets had a certain reliability and applicability in urban flood modelling if the measured data of inlet nodes were unavailable. ② The ponding depths and waterlogging nodes were simulated by the SWMM model using the catchment hierarchical partition method, the Thiessen polygon combined with the hydrology method, and the Thiessen polygon method. The simulated maximum ponding depths obtained from these three catchment partition methods accounted for 100%, 63% and 75% of the actual inundation degrees. About 80.0%, 76.4% and 77.4% of the simulated waterlogging nodes were consistent with the waterlogging risk map for a 5-year rainfall return period. The simulated results obtained from the catchment hierarchical partition method were more accurate than the results from other two partition methods. It is found that the simulated results from the catchment hierarchical partition method was relatively consistent with the actual real waterlogging situation. ③ In terms of the 5-year rainfall return period, the simulated flooding obtained from these three methods had a small influence on the urban management. However, different degrees of waterlogging would occur for the rainfall return period greater than 5 years. This study can provide a new method for the discretization of ground surfaces and the determination of inlet nodes in simulating urban rainstorm floods, and provide the reference for urban flood control and disaster reduction.