Simulation Study Of Typical LID Measures On Surface Runoff Control Process

In recent years,the rapid development of the national economy has promoted the urbanization process in China,and the rapid urbanization process has lead to confusion in the layout of urbanization,which has further led to the frequent occurrence of waterlogging,deterioration of water bodies,waste of rainwater resources and other problems.The "Sponge City" put forward by our country has become the main construction idea to solve the current problems.Meanwhile,as the main implementation measure for Sponge City construction,the Low Impact Development(LID)model with source control as the core has begun to prevail in China.However,due to the short construction time of Sponge City in China,the planning,construction and evaluation system is not perfect,and the planning goals and realization approaches in some areas are out of line.In order to avoid the actual effect not meeting the design requirements,this paper used a model method to study the details of Sponge City construction from the LID perspective,so as to facilitate people to timely find and adjust design defects in sponge city design.The core content of this paper is divided into the following three parts:(1)The model was modeled before and after the actual sponge reconstruction based on SWMM model,and the Nash-Sutcliffe Efficiency coefficient(NSE)was used as the evaluation index of the simulation results to check the model.According to the fitting curve between the actual monitoring results of the single rainfall event after the sponge modification and the simulated overflow discharge,it can be considered that the peak value and duration of the overflow are consistent with the monitoring results.At the same time,NSE > 0.7,it can be seen that the model simulation results are in good agreement with the monitoring data.Therefore,it is believed that the model constructed in this paper is relatively accurate and can be used to evaluate whether the actual construction effect can reach the planning goal.;(2)Under different rainfall intensity conditions,the effects before and after sponge city transformation were simulated and analyzed,that is,the runoff control rate,node overflow and discharge peak were analyzed respectively.Through simulation,it was found that adding LID facilities could improve the runoff control rate in the study area under different rainfall intensity.The number of node overflow also decreased significantly with the addition of LID facilities.With the increase of rainfall intensity,the delay time of drainage peak decreases gradually.Therefore,LID facilities have a better control effect on low-intensity rainfall events;(3)To further explore the runoff control effect of typical LID facilities,select reasonable parameters,and optimize and explore the regularity of LID facility parameters through simple model and response surface analysis.Taking vegetation gully as an example,in the SWMM model constructed with vegetation gully facilities only,According to the response surface,the influence order of the selected three parameters on the runoff control rate is area ratio > maximum permeability rate >width.The optimal scheme is as follows: area ratio A is 37.39%,width B is 0.50 m,maximum permeability rate C is 253.23 mm /h,and the predicted runoff control rate is 78.6%.At the same time,the above optimization method is also applicable to the optimization of other LID facility parameters.Specific influencing factors need to be determined after sensitivity analysis based on selected evaluation indicators.