Study On The Tiered And Whole Process Stormwater System Planning In The Rainy Area Of Southern China Under The Background Of Sponge City

Stormwater system as a critical infrastructure of the city,to alleviate the waterlogging,maintaining water balance is important.However,with the increase of impervious area and the extreme rainstorm in the process of urbanization,the urban surface runoff shows a trend of large flow,high peak and fast flow,which leads to the increase of the load of urban drainage network and the increase of waterlogging risk.The construction of sponge city with natural accumulation,natural infiltration and natural purification is an important measure to solve these problems.Based on the present situation and existing problems of sponge city construction,this paper divides the model of stormwater control and utilization in sponge city,and constructs the tiered and whole process stormwater system for rainy southern area.The main research contents are as follows:(1)From the natural point of view,this paper build the sponge city under the "infiltration,stagnation,storage,net,use,row" six urban stormwater system,to achieve stormwater runoff seepage,Flood storage,water purification,storage and reuse,transfer emissions six functions,pointed out the concept of each subsystem,technical measures,the main functions and scope of application.(2)In view of the shortcomings of the current pattern of stormwater control and utilization in different regions of China,the precipitation,temperature,soil and drought and flood disasters were extracted by using principal component analysis(SPSS)based on SPSS software as the four main component influencing indexes.The stormwater control and utilization patterns in the construction are divided into four regions: the southern rainy region,the central warm temperate region,the northeastern cold region and the northwest dry area.(3)The tiered and whole process stormwater system is built in the rainy areas which have most serious problems in waterlogging.Different levels of treatment systems should deal with different rainfall events and realize different runoff control targets.The basic unit infiltration system is suitable for dealing with the rainfall return period(0.5~1a),the garden reduction system deals with the rainfall return period(1~3a),the plot layer of stagnation system for dealing with the rainfall return period(3~5a),the end of the regulation system is suitable for dealing with the rainfall return period(5~10a).(4)Taking the typical city of Nanchang as an example,the layout design and SWMM model of the tiered and whole process stormwater system are studied in this area.The results show that the tiered and whole process of stormwater system is effective in reducing the total runoff,peak flow,delaying the peak time,reducing the runoff coefficient,reducing the overload pipe and the overflow node,and ensuring that the rainfall does not overflow facing the rainfall return period(10a)when the basic does not affect the normal life.And the different levels of the stormwater system to the stormwater runoff reduction,to achieve the goal of "light rain no ponding,heavy rain no waterlogging".