Urban Rainstorm Flooding Simulation Considering Complex Surface Information

The urban flooding caused by the rapid urbanization process has become an urgent urban disease.Therefore,the accurate and rapid simulation of urban inundation area and depth under different rainstorm scenarios is of great significance for timely and effective assistance to government decision-making and reduction of urban inundation losses.Firstly,with the support of multi-source data such as high-resolution remote sensing images,high-precision DEM and drainage network,this research propose an improved catchment delineation method by considering the complex urban surface to improve the simulation accuracy.Then,by coupling one-dimension model(SWMM-based refined runoff and confluence model)and two-dimension(inundation diffusive process simulation model based on complex surface)hydrological and hydrodynamic models,the Urban Rainstorm Flooding Coupling model considering complex Surface(URFCS)is constructed.URFCS fully utilizes the accuracy advantages of the SWMM model in the simulation of small-scale urban flooding.It overcomes the defect of SWMM that cannot simulate the spread of two-dimensional surface water accumulation and achieves the accurate simulation of inundation area and depth.Finally,taking Haining City,Zhejiang Province,which has frequent rainstorms and flooding as the study area,the URFCS is verified by several historical rainstorm events.On this basis,the urban flooding simulation study was carried out under different return period scenario.The results show that:(1)The catchment delineation method by considering the complex urban surface fully considers the influence of the urban terrain fluctuations and the drainage pipe network on the hydrological process and improves the rationality of the catchment delineation.It is more suitable for the input rules of the SWMM model and effectively improves the accuracy of the input parameters of the SWMM model.At the same time,URFCS solves the defect that the SWMM model cannot get the two-dimensional surface inundation results.It converts the one-dimensional overflow flow results obtained by the SWMM to two-dimensional inundation area and depth results by considering the complex surface.(2)The three historical storm events(20180620,20180803,and 20180820)simulation results show that the correlation coefficients of simulated inundation depths and measured inundation depths are 0.88,0.83,and 0.85,respectively.The simulation accuracy is high,which indicates that the URFCS model can accurately simulate urban flooding information.(3)Under four different storm scenarios(5-,10-,20-and 50-year return period,respectively),the maximum inundation depths are significantly increased from 158 cm to 322 cm and the maximum inundation area increased from 2904 m2 to 7330 m2.It shows that storm intensities have a significant effect on the degree of flooding.According to the simulation results,Haining Avenue,Sanshui Park and the old residential area in the study area would encounter the most extensive and severe inundation.The URFCS model is suitable for the simulation of urban flooding in small-scale urban areas,which contributes to a more detailed understanding of storm runoff and inundation processes and provides better insights and tools for urban flooding simulation and planning strategies.