Design Methods Of Urban Stormwater System Withlow Impact Development Application

In recent years, with water resource shortages, frequent urban waterlogging andinitial rainwater pollution problems increasingly prominent, rainwater utilization anddischarge technology would get more and more attention and application, especially lowimpact development technology had rapidly developed, China’s outdoor drainage designspecification was also more and more attention to rainwater discharge and theapplication oflow impact development technology. The application of low impactdevelopment technology would reduce the runoff coefficient of the area, change thewater catchment area of the set time, and make the drainage and utilization systemcompared with the traditional separate system of drainage system differences.Therefore,after using low impact development technology, storm sewer drainage designflow and the calculation formula of a storage pool volume may changes. While past andcurrent specification for design of outdoor drainage in our country didn’t give thedesign method of the rain water discharge and utilization system under low impactdevelopment, so it is urgent to design separate storm sewer flow system of low impactdevelopment model and storage tank volume calculation method research.In this paper, the situation of rainwater utilization and the volume calculationmethod of storage pool were summarized and analyzed at home and abroad, andtheoretically analysed rain water pipe design and volume calculation method of thestorage pool under low impact development model, based on the use of SWMM modelto simulate low impact development technology on the reduction effect of peak runoffand total runoff, and the removal efficiency of pollutants. The results of the study wereas follows:①The author analyzed different types of separate system of rainwater storagetanks, and put forward different rainwater storage tank system in the separatesystem.Based on the summary of domestic and international rainwater storage tankvolume calculation method, the paper gived rainwater storage tank volume calculationprocedure and method suitable to our country.②Analyzed the types of low impact development technology, and studiedrespectively rainwater drain ditch design traffic volume,storage pool and subsequenttube drainage design flow after setting a storage pool in the separate rain system with abiological stranded, rainwater infiltration (including rain water pipe canal design return period P is less than or equal to and greater than rainwater infiltration facilities designreturn period of two cases), and retention use facilities.③A district in chongqing as an object to study the rainwater system design methodwith the application of low impact development technology of using rainstorm runoffmanagement model (SWMM model), the reduction of runoff and pollution werecompared before and afterusing low impact development technology.Calculated, whenthe return period of the design rainfall was5~20a: the reduction rate of runoff volumeof the35.07%sunken green was34%~42%, the reduction rate of runoff volume of the11.88%permeable pavement was23%~23%, and the reduction rate of runoff volumeofthe28.91%green roofs was46.99%~46.99%;the removal rate of TSS, COD, TN ofthe35.07%sunken greenwere15.3%~23%,14.06~22.9%and14.41%~28.41%; theremoval rate of TSS, COD, TN of the11.88%permeable pavement were23%~23.5%,20.17%~24.33%and23.5%~20.17%; the removal rate of TSS, COD, TN of the28.91%green roofs were44.37%~47.93%,44.14%~47.19%and44.14%~51.48%.