| In recent years,China’s urbanization process has been speeding up,and the construction of cities has caused an increase in hardened ground,which has caused serious waterlogging and non-point source pollution problems.Low Impact Development(LID)is an emerging concept proposed in the process of urban development.The goal of LID is to restore or maintain a natural state as much as possible.It can also be used as an improvement measure to reduce rainwater runoff,pollutant loads and impacts on body of water in certain area.This article takes Northwest University’s Chang’an campus as the research area,collects relevant data to establish a SWMM model and design a LID facility layout plan.The main research results are as follows.(1)The study area is divided into 12 plots according to different functions.Each plot is individually designed with a LID scheme.The weighted average of the annual runoff control rate of the plots reaches 80.9%,which is in line with the guidelines for planning and design of sponge cities.(2)Under different periods of rainfall recurrence,the total outflow reduction range of the LID scheme in the study area can reach 2.211×10~6L～3.502×10~6L,the outflow reduction rate can reach 21.53%～44.89%,and the flood peak reduction can reach 0.04 m~3/s～0.24m~3/s,the flood peak reduction rate can reach 2.92%～24.24%.The LID scheme has a good control effect on the total amount of rain and outflow in the study area.With the increase of the rainfall recurrence period,the various indicators of the outflow,flood peak gradually decreased,indicating that the regulation effect of LID gradually decreased with the increase of the rainfall recurrence period.(3)During different periods of rainfall recurrence,the deployment of the LID scheme can effectively improve the operation of the drainage pipe network.The reduction rate of the overloaded pipe network ranges from 17.48%to 33.90%,and the reduction rate of the node overflow is 47.77%～59.01%.With the increase of rainfall recurrence period,the pipe network overload and node overflow reduction rate gradually decreased.(4)With the increase of the rainfall recurrence period,the non-point source pollution load caused by the rainwater gradually increases.The deployment of LID can greatly reduce the non-point source pollution load and the peak concentration of pollutants at the outfalls,and at the same time with the rainfall recurrence period increases,the reduction effect of LID measures on non-point source pollution load and peak pollutant concentration gradually decreases,indicating that LID is more suitable to be deployed in areas with less rainfall intensity,but LID has good non-point source pollution reduction effect under each rainfall recurrence period. |
