Simulation Of Rainfall Runoff Based On SWMM And Analysis Of LID Combination Scheme

The rapid urbanization process changes the type of urban underlying surface,increases the water permeability ratio and frequent waterlogging.In order to solve such problems,China proposes to build a springe city using low impact development techniques.This study is based on China's insufficient concept of rainwater management,combined with foreign leading technology to improve the control of rainfall runoff technology.In this paper,a SWMM model basing on one certain research area in Xi'an City was established,it simulated the rainfall runoff law and the influencing factors of the underlying surface of each drainage zone under conventional development.The long-duration rainfall processes under different recurrence periods were obtained through the frequency analysis method,and the LID development of five combined schemes was earned out in the research area,a comprehensive evaluation was advanced on the schemes in terms of flood control effects,investment costs,and social benefits.The AHP analysis method to construct a judgment matrix for energy efficiency analysis was adopted to make optimal evaluations on each of the scheme.The main research results arc as follows:(1)Analyzed the causes of waterlogging in Xi'an City,by combining the actual situation,the sub-catchment area and drainage pipe network were generalized in the research area,and the types of underlying surfaces were divided.Verified the model parameters by using the comprehensive runoff coefficient method,which showed the established model was equipped with good applicability and prediction accuracy.(2)A simulation was carried nut based on the SWMM model for the short-durulinn heavy rain process under the conventional development,the influence laws were obtained for different rainfall recurrence periods and rain peak coefficients on the flood peak of characteristic value of rainfall in the Fiver basin outlet,the flood peak occurrence time,the flood volume and the underlying surface runoff coefficient.(3)Analyzed in terms of the simulation results after the LID development,in the context of long-duration rain recurrence period in 24 hours,the five combined schemes had a very good reduction effect on the total emissions,peak runoff,and runoff coefficients of the overall system,but as the return period increased,the reduction rate has gradually remained unchanged.(4)Combined the three evaluation indicators to evaluate the LID combination plan,the scheme two(permeable paving+sunken green space+green roof+rainwater tank)was finally obtained to become the LID combination measures with the best comprehensive benefit.It proves that the application has certain rationality in the actual LID development.