Scenario simulation study on urban rain flood control under the combination of low impact development facilities
[Objective]As a new rain flood management method,low impact development(low impact development,LID)in-cludes typical measures such as green roof,rain Water garden,permeable pavement and so on.It has obvious control effect on rainfall runoff and can effectively reduce the hidden danger of urban waterlogging.[Methods]Taking Haining City,Zhejiang Province as an example,based on the rainstorm flood management model(Storm Water Management Model,SWMM),the urban waterlogging process was simulated under different return periods(1a,5a,10a,10a,50 a)and different arrangement ratios(20％,50％,100％)of LID combined measures,analysis of the distribution,degree and causes of overflow in Haining City.The effects of LID combination measures in overflow area on node overflow,surface runoff and pipe network load are discussed.[Results]The result show that the pipe network overflow is more serious in different design rainfall scenarios,such as Union Road,Haichang Road,Shuiyueting West Road,Xishan Road and Longxing Port.When the proportion of LID combined meas-ures is the same,the weakening effect of LID combined measures on surface runoff and node overflow tends to decrease with the increase of return period.The effect of LID measures tends to be saturated,with a return period of 30 a and 50 a,and when the layout ratio is 50％,the reduction of surface runoff is 45.92％and 44.09％respectively.[Conclusion]The control effect of LID combination measures on rain flood is limited,and rainfall intensity plays a leading role in node overflow and surface runoff.In the case of extreme rainstorm,the influence of rainstorm on runoff and node overflow is dominant.The years of pipelines in some old residential areas in Haining City are longer,the diameter of pipes is shorter,and the overflow of pipe networks is serious.It is suggested that we should focus on the reconstruction of regional pipe networks and the spatial layout of LID measures.The re-search result have a certain reference value for sponge city construction planning and mitigation of urban waterlogging disasters.
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