Study On The Construction Of Urban Double Drainage System Based On The Idea Of Grey-Green Infrastructures’ Linkage

With the continuous progress of urbanization and the continuous change of urban ecosphere,environmental problems of China now is so severe.In the rainwater field,the frequency and impact range of urban waterlogging and flooding are significantly increased.Because of the complexity of urban system composition and structure,the traditional development concept and the LID concept used today are incomplete in theoretical depth and advanced degree.Therefore,a new design and development concept of rainwater system is needed to provide guidance for the construction of new urban rainwater system.Accordingly,this paper puts forward the concept of "grey-green" facility coupling,which emphasizes that there should be positive coupling among different subsystems,rather than simply superposition of functions.After that,based on the concept of "grey-green" facility coupling,this paper proposes a new urban rainwater system-urban double drainage system planning method.Through the process of subsystem coupling and compounding,the vertical drainage pipe network can be constructed,and the drainage function of rainwater system can be maximized.Finally,the system effect is verified and evaluated by SWMM model.The main contents of this paper are as follows:(1)Analyzing the research and development process of rainwater system design concepts at home and abroad,summing up the advantages and disadvantages of different design concepts in the current situation,and combining with the new situation of urban development,clearly put forward the concept of "grey-green" facility coupling,in order to strengthen the coordination between different subsystems by coupling,and truly achieve the purpose of strengthening the interaction between rainwater control units.(2)Based on the concept of "grey-green" facility coupling,this paper perfects the defect of the previous double drainage system theory which is limited to the role between surface and pipeline runoff,puts forward the theory of urban double drainage system,and makes a complete description of the characteristics of the double drainage system: overall coupling regulation of steady state,design thinking to cope with the limit,material and information dual flow.At the same time,the composition of "front infiltration-middle transfer-excessive storage-tail discharge" of the double drainage system is determined,and its hydrological and hydrodynamic principles are analyzed and studied,and the SWMM model for the effect evaluation of the double drainage system is selected.(3)Taking Lichuan County,Fuzhou City,Jiangxi Province as the research area,SWMM model was established and double drainage system was reformed to verify the work effect of double drainage system under different rainfall situations in the recurrence period.Runoff control rate,waterlogging control design standard and "grey-green" concept were used as evaluation criteria.Finally,it was concluded that rainfall occurred in the recurrence period of 0.5a,2a,5a,10 a,20a and 50 a.At birth,the runoff control rates of double drainage systems are 80.21%,73.09%,65.78%,61.11%,57.20% and 54.02% respectively,which exceed the effect of traditional rainwater systems,and the system can meet the requirements of waterlogging control standards and "grey-green" concept.