Evaluation Of Sponge Effect In The Residential District Of The Sponge City

In recent years,with the acceleration of China’s urbanization process,many urban areas have unreasonable planning problems.As the impervious surface has increased significantly during urban construction,and as rivers,lakes,natural waters,wetlands,and green areas have been invaded,the hydrological processes had been affected,and rainfall infiltration,stagnation,purification,and evaporation have been greatly reduced.On the one hand,the total amount of runoff and peak flow in the urban rainy season increases greatly,causing serious threat to urban safety,people’s life and property.On the other hand,the effective utilization level of rainwater resources is not high in the background of the increasingly scarce of urban water supply.In order to solve these problems,the state has put forward the concept of the Sponge City which is to improve the capacity of retaining and purifying rainwater in new urban areas and old areas by using methods such as seepage,stagnation,storage,net,use,and rowing to solve the problems of urban rainwater environment,urban rainwater use,water quality and water safety.Since 2013,more than 30 cities have obtained national pilot projects for sponge cities,but for the evaluation of Sponge City effects,there is still no unified and clear methods in China.This paper mainly studies the evaluation of effects of Sponge City,the main research results are as follows:(1)First part of this paper is the construction and application of the evaluation system of spongy effect of Sponge City.In the construction of sponge effect evaluation system,Delphi method and AHP methods were used to built the valuation system and fuzzy comprehensive evaluation method used to evaluate the effects of Sponge City.After the target selection and the expert reelection,the evaluation index system aimed at Beijing is finally determined.The evaluation contents include four aspects including resource utilization,waterlogging prevention and control,environmental improvement and engineering impact,and 10 evaluation indexes.The weight system is determined by expert scoring.The results showed that four most influential indicators,whose weight index is 0.474,are the rainwater storage module,the annual rainwater utilization rate,the green subsurface concavity,and the hardened surface permeability ratio Fuzzy comprehensive evaluation method was used to evaluate the effects construction of Sponge City on Beijing Shuangzi District and the results showed that the performants in resource utilization and waterlogging prevention and control were excellent and in environmental improvement and engineering influence were good.Overall evaluation result of Shuangzi District plot is excellent.(2)The second part of this paper is evaluation of runoff control effect.The SWMM model was applied to simulate Volume Vapture Ratio of Annual Rainfall in the Shuangzi District.Reslults showed that the total amount of runoff was reduced by 94%,the peak of runoff was reduced by 95%,and the peak time was delayed by 15 min.After heavy rainfall,the total runoff volume was reduced by 94%,the runoff peak value was cut down by 50%,and the peak time was delayed by 5min.After rainstorm,the total runoff volume is reduced by 73%,the runoff peak value is reduced by 36%,and the peak time is delayed by 0 min.From the design rainfall simulation,we know that the total amount of runoff reduction is the most obvious,followed by the peak flow volume reduction and the peak time.(3)The third part of this paper is the relationship between runoff reduction and the scale of sponge measures.The effect of Volume Vapture Ratio of Annual Rainfall is evaluated by annual runoff total control rate.First,t Volume Vapture Ratio of Annual Rainfall is calculated,and then the rainfall design of 1 years,2 years and 3 years(1H,2h,3H)is carried out through the rain type generator in Chicago.Volume Vapture Ratio of Annual Rainfall can be calculated by different design rainfall.When the control rate of a design rainfall is the closest to 94.9%,the design rainfall can be used as the model rainfall input item,the typical rainfall,to simulated effects of scale of sponge measures on runoff reduction in different working conditions(changing the permeability ratio of the hardened pavement and the storage modulus of the rainwater).The results showed that inally determining the building.Above all,the standards system of Volume Vapture Ratio of Annual Rainfall based on the permeable paving and the storage pool was carried out,in which the permeability ratio of hardened pavement is 80%,and the storm water storage modulus is 0.4%.