Study On Identification And Optimization Of Waterlogging-prone Area Based On SWMM

In recent years,with the continuous advancement of research on low impact development(LID)measures and the gradual improvement of urban drainage and waterlogging prevention management,urban waterlogging in China has been alleviated,but waterlogging events in residential areas caused by heavy rainfall still occur from time to time.In this regard,on the basis of fully analyzing the characteristics of the current drainage and waterlogging prevention system in a residential area,through the construction of storm water management model(SWMM),the accurate identification of waterlogging points and the optimization and effect evaluation of drainage and waterlogging prevention design scheme in residential areas are carried out.The research results have certain theoretical and practical significance for improving the drainage and waterlogging prevention ability of residential areas.By analyzing the short-duration heavy rainfall events in the study area,the SWMM model is used to explore the drainage capacity of the current rainwater system in the residential area under different return periods.The results show that when the rainfall is50.89 mm(once in 10 years),the overflow time of the overflow catchment node is less than 15 min,and the inflow of the back-end rainwater collection pipeline is within the range of its carrying capacity.The short-term accumulated water in the corresponding area can be discharged in time,and there is no waterlogging in the community.When the rainfall increased to 62.95 mm(once in 20 years),the catchment node with overflow time more than 15 min began to appear,and the inflow of the rear rainwater collection pipeline exceeded its carrying capacity(pipeline overload phenomenon).The corresponding area had serious water accumulation,and the waterlogging risk increased significantly.When the rainfall further increased to 77.37 mm(once in 50 years),it exceeded the design drainage capacity of the rainwater pipe in the residential area.The proportion of overflow nodes and overload pipes increased significantly,and the waterlogging phenomenon in the residential area further intensified.Based on the above research,the judgment conditions of waterlogging points in residential areas are proposed,and the types of waterlogging points and their causes are verified by analyzing the overflow of each catchment node and the full load of pipe and canal under different return periods.The results show that under the condition of the design return period of 20 a,taking whether the overflow time of the catchment node exceeds 15 min as the judgment principle,there are 9 waterlogging-prone points in the area,which are mainly distributed at the junction of the pipeline(J5,J16,J21,J22),the end of the rainwater collection pipe network(J4)and the low ground permeability areas(J24,J25,J26,J27).Analysis of the reasons,the connection point of the pipe section and the end node transfer upstream sub catchment area rainfall is large,resulting in excessive drainage tasks.The low infiltration in the area with low surface permeability leads to a significant increase in surface runoff and increases the risk of waterlogging.According to the characteristics of the underlying surface conditions and space site requirements in the study area,the permeable pavement,biological detention facilities and rainwater storage facilities were selected to carry out LID reconstruction of the vulnerable points,and the actual drainage capacity of the transformed residential area was analyzed.After modification,when the actual rainfall is 56.5 mm,there is no overflow node and water accumulation in the area.When the actual rainfall increased to 68.5 mm,the comprehensive runoff coefficient decreased from 0.85 to 0.48,and the number of overflow nodes decreased to 2.The reduction rate of overflow nodes was 94%,and the maximum overflow time was only 4 min.There is no rainfall with a return period of 50 years after the reconstruction,so the SWMM model is used to simulate the drainage capacity of the pipe network under this condition.The results show that the maximum overflow time of the node is 12 min.In conclusion,the LID reconstruction of waterlogging-prone points in residential areas can effectively improve the node overflow,significantly improve the drainage and waterlogging prevention ability of residential areas,and provide reference for the reasonable sponge transformation of residential areas.