Research For The Construction Path And Control Target Of Sponge City In Wuhan

Urban waterlogging disasters are growing increasingly severe along with the accelerating rate of urbanisation.The construction of sponge cities based on LID technology can effectively address such problem from its source.Wuhan has many problems in water safety,water environment,water ecology and water resources.Changing the traditional development model and creating a natural sponge city has become an important topic in Wuhan,and the study of LID measures and control objectives suitable for Wuhan is of great significance to the sustainable development of the city.This paper used two different scale SWMM models to explore the control objectives and technical measures for the construction of sponge cities in Wuhan.The small-scale model of new community was used to determine the setting criteria of LID combination measures that meet different control objectives;The large-scale model of catchment area was used to evaluate the effect of the set standards.According to the simulation analysis,field investigation and demonstration,the main research results obtained in this paper are as follows:(1)The setting standards of LID measures for new residential districts in Wuhan were obtained by simulation:The proportion of depressed greens,pervious pavements and green roofs should be 30%,70%and 50%,accounting for 15%,6%and 12.5%of the total area.The proportion of LID settings for other different land types in Wuhan was also proposed.(2)The combination measures of LID and split storage tanks should be adopted to control peak flow and waterlogging;the setting standard of split storage tanks in the combined measures of controlling peak flow rate in parcel level of Wuhan city:a.If the green roof can be set up,it should be set up with 210m~3/hectare impervious pavement and 0.1m offset;B.If the green roof can not be set up,it should be set with280m~3/hectare impervious pavement and 0.05m offset.(3)The combination measures of LID and closure storage tanks should be adopted to control volume capture ratio of annual rainfall,non-point source pollution and rainwater resource utilization.The setting standard of closure storage tanks in the combined measures of controlling volume capture ratio of annual rainfall in parcel level of Wuhan:a.If the green roof can be set up,it should be set according to the standard of 194,268 and 371m~3/hectare impervious pavement(corresponding to 75,80 and 85%volume capture ratio of annual rainfall);b.If the green roof can not be set up,it should be set according to the standard of 180,260 and 370m~3/hectare impervious pavement(corresponding to 75,80 and 85%volume capture ratio of annual rainfall).In order to improve the reduction rate of non-point source pollution,the closure storage can be divided into initial rainwater storage area and later rainwater storage area:a.If the green roof can be set up,the initial rainwater storage tank can be set up with 61m~3/hectare impervious pavement;b.If the green roof can not be set up,the initial rainwater storage tank should be set up with 46m~3/hectare impervious pavement.(4)Based on the investigation of the source of the sponge transformation plot in the delta lake catchment area of Jingkai District in Wuhan and the LID setting standards of parcel level in Wuhan City,depressed greens,pervious pavements and green roofs account for 9.40%,2.85%and 5.00%of the total area.The combined measures of LID have a certain reduction effect on the runoff and peak flow,but with the increase of recurrence period,it is weakening.(5)On the basis of LID combined measures,split storage tanks were added.The drainage capacity of the pipeline and the water accumulation of the nodes in the delta lake catchment area have been improved and alleviated,and the reduction effect of peak flow and runoff have been better.On the basis of LID combined measures,closure storage tanks were added to control the total annual runoff in the delta lake catchment area,and the total annual runoff in the area has been well controlled.The volume capture ratio of annual rainfall in the region reaches 79.93%.The setting standards of technical measures and their effect evaluation obtained from the simulation analysis can provide technical support for the construction of sponge city in Wuhan.