Study On Optimization Of Low Impact Development Measures Of Furong Avenue Based On SWMM

This study is based on the "sponge" transformation of existing roads,and based on SWMM software,by comparing the effects of various road LID facilities,we can get the appropriate optimization strategy of road reconstruction,hoping to provide reference for the "sponge" construction of existing roads in other urban areas.Firstly,SWMM model software is introduced in detail from the aspects of software introduction,rain pattern selection and calculation theory.The results of simulation calculation are checked by the results of theoretical calculation,and compared with the results of theoretical calculation and actual simulation calculation in relevant literature.The sensitivity analysis of relevant parameters is carried out,which facilitates the completion of subsequent parameter calibration work.This paper analyses the characteristics of low-impact Road Development and design at home and abroad,summarizes the LID facilities suitable for existing road reconstruction,compares and chooses various low-impact development facilities,and draws a preliminary LID layout scheme.Secondly,the SWMM model is established according to the design drawings and design specifications of Furong Avenue in Xiangtan City;three rainfall events provided by Xiangtan Hydrological Bureau are input for parameter calibration;and the rainstorm formula of Changsha City is numerically inputted using Chicago Rainfall Editor to simulate the recurrence periods of 1a,2a,3a,5a,10 a,15a,20 a,30a,50 a,100a.Rainfall series;input each recurrence period into the model and LID facility parameters into the model;simulate the rainfall and flood respectively,and derive the total runoff,runoff start time,peak flow and peak time.Thirdly,LID facilities without LID facilities,permeable asphalt,permeable bricks and grass planting ditches are simulated separately,and the total runoff reduction effect,the delayed effect of runoff start time,the reduced effect of peak flow and the delayed effect of peak flow occurrence time under different rainfall recurrence periods are analyzed.The effects of single LID facility under different rainfall recurrence periods were compared and analyzed,including total runoff reduction,runoff start time delay,peak flow reduction and peak flow occurrence time delay.Finally,three LID facilities are combined into four road optimization schemes: permeable asphalt + permeable brick(scheme 1),permeable asphalt + vegetation ditch(scheme 2),permeable brick + vegetation ditch(scheme 3),permeable asphalt + permeable brick + vegetation ditch(scheme 4).Four combined LID facilities are analyzed from four aspects: total runoff reduction effect,delayed effect of runoff start time,peak flow reduction effect and delayed effect of peak flow occurrence time.The concrete effect of each combined LID facility is obtained.Four combined LID facilities are compared and analyzed,and the optimum results are obtained.Combination LID facility,put forward the optimization strategy of LID facility suitable for this road.When the recurrence period of rainfall is 1a and 2a,no runoff will occur after the fourth plan is laid out.When the rainfall recurrence period is 1a,2a,3a,5A relative high-frequency rainfall,the reduction rate of total runoff is 92.16%,88.58%,84.77%,78.34% respectively,and the best reduction effect is achieved.When the rainfall recurrence period is 10 a,15a,20 a,30a,50 a,100A relative low-frequency rainfall,the reduction rate of total runoff is 46.38%-69.81%,which is very good,but next to that of low-frequency rainfall.High frequency rainfall.When the rainfall recurrence period is 3 years relative to high-frequency rainfall,the delay of runoff start time is as high as 41.4 minutes,but the delay of other relative low-frequency rainfall runoff start time is 9.4-23.9 minutes,the delay effect of high-frequency rainfall is poor.When the rainfall recurrence period is 1a,2a,3a,5A relative high-frequency rainfall,the reduction rate of peak flow is 91.49%,90.64%,85.71%,78.23% in turn,and the best reduction effect is obtained.When the rainfall recurrence period is 10 a,15a,20 a,30a,50 a,100A relative low-frequency rainfall,the reduction rate of peak flow is 41.07%-68.57%,the reduction effect is very good,but once.Rainfall occurs at high frequencies.When the recurrence period of rainfall is 3 years,the time delay of peak flow is as high as 55.6 minutes,but the time delay of peak flow of other relative low frequency rainfall is 10.2-34 minutes,which is good,but second to high frequency rainfall.