Technical Analysis And Design Of Tianjin Stormwater Systems With Considering "Sponge City" Concept

Tianjin water environment is faced with many problems,such as water shortages,serious river pollution during flood season,drainage facility of low standard,difficult to discharge excessive rain,combined sewer and the mixture of storm and sewers.This paper puts forwards "sponge City" as a guide,establishes multi-objective and institutional framework for multi-angle overall integrated water resources management.Three links,includes LID rain water facilities and improve standards river pollution prevention,should be contained to build Tianjin urban water environment.(1)Centering on the construction of Tianjin "sponge City",the traditional drainage facilities and low-impact development system are closely combined,the improvement of the drainage capacity is focused on,the discharge of initial rainwater and combined sewage into river should be reduced,It is stressed that the reduction at the source and the midway and the regulation and storage at terminal to reduce total runoff,peak runoff and runoff pollution;(2)The influence of the recurrence interval P and reduction factor m contribute to stormwater design flow is analyzed;The ration to present and improved water system is calculated for first district and second district.(3)The main source of the water contamination is the discharge of initial rainwater and combined sewage into river during flood season,To control water pollution,combined sewer and initial rainwater diffuse runoff should be eliminated,the sediment dredging should be conducted and water flowing should be strengthen;the feasibility of using rainwater pipes as rainwater storage space,using surplus amount of sewage pipe network to exclude initial rainwater is analyzed,specific ways of governance is identified;(4)Tianjin Balitai is selected as an example of the new district to research the construction of LID.The total annual runoff and stormwater peak efflux are the targets of LID for the new district.After the calculation of total amount of new residential runoff,low-impact development facilities volume,a set of sunken lawn,permeable paved road,bio-retention zone,storage tanks,etc.are built,goals of annual runoff control rate 85 %,comprehensive rainfall runoff coefficient of 0.4,the integrated flow runoff coefficient of 0.53 are achieved;Without changing the municipal stormwater system,the peak flow is cut down and the recurrence interval increases from P = 0.4 to P = 3;(5)The Hedong District of Tianjin,Zhongshan Gate residential area is selected as a LID stormwater system transformation example under the old district,through the reasonable arrangement of the development facilities,such as sunken lawn,permeable paved road,bio-retention zone,goals of annual runoff control rate 70 %,comprehensive rainfall runoff coefficient of 0.49,the integrated flow runoff coefficient of 0.9 are achieved.