LID Scheme Optimization Design And Effectiveness Evaluation Of Sponge City Road Based On SWMM

Disasters such as city waterlogging occurred frequently with the development process of urbanization being accelerated today.To solve this problem,sponge city concept and LID(Low impact development)technology came into being,which can effectively control rainwater runoff and pollutants.In this thesis,Shiji Road in Xixian New District of Shaanxi Province and its surrounding areas are taken as the research area.On the basis of fully investigating surrounding meteorological,hydrological and water quality data,a regional generalization model is established with CAD plane plan and SWMM simulation software.LID facilities are selected according to the selection principle of LID control facilities.Including permeable pavement,biological retention pond,grass ditch and infiltration canal,four combination schemes of LID control facilities are constructed by using four facility designs.Hydrology mainly simulates infiltration loss,surface runoff,water storage,peak discharge,peak time and node overflow.Water quality simulates the reduction of TSS,COD,TN and TP pollutants by the four schemes.In the selection of efficiency evaluation indexes,the comprehensive fuzzy evaluation method and expert questionnaire method were used to select 13 evaluation indexes from three aspects: environmental benefit,social benefit and economic benefit.By means of expert questionnaire,the 1-9 scale method is used as the standard to form the judgment matrix and the analytic hierarchy process is used to construct the judgment matrix.The consistency of the judgment matrix is tested and its weight is calculated.The evaluation criteria and evaluation model of quantitative index and qualitative index were established respectively.The comprehensive efficiency of the four schemes was evaluated and compared,and the optimal scheme was designed for road cross section and plane layout.According to the simulation data and efficiency evaluation results,the four schemes have good control effect on peak time,peak flow reduction rate,runoff control rate and node overflow in hydrology,and have good removal effect on TSS,COD,TN and TP in water quality.According to the comparison of hydrology and water quality performance and efficiency evaluation results of the four schemes,the hydrology and water quality treatment effect of the first scheme(permeable pavement + biological retention pond + leachate)is the best,which can be preferred when the funds are sufficient.The fourth scheme(permeable pavement + leachate + grass ditch + biological retention pond)has the lowest cost and maintenance cost,and the treatment effect of hydrology and water quality is second only to the first scheme.Option four can be selected when considering economy.Scheme 2(permeable pavement + biological retention pond + grass ditch)and Scheme 3(permeable pavement + grass ditch +seepage canal)have the lowest priority.This study finds out the technical advantages that are conducive to the study area(and the local area)to achieve the annual runoff total control rate,reduction rate of main runoff pollutants and other key control targets of sponge city construction,which can provide an empirical reference for the subsequent sponge city construction of other cities/towns in the nearby area.In the long run,it may have more important engineering application value.