Quantitative Study On Benefits Of The Urban Low Impact Development Stormwater System

The lack of urban water resources,serious pollution of water bodies,frequent waterlogging and the continuous decline of groundwater level have become the main reasons for restricting the sustainable development of cities in China.Therefore,China has proposed the construction of "sponge city" with natural accumulation,natural infiltration and natural purification on the basis of low impact development.At present,the construction of the sponge city is mainly based on the direct investment of government,the degree of marketization is low,and the financing channels are relatively simple,the performance evaluation system is not mature as well.The quantitative evaluation of the comprehensive benefit of the sponge city has become the key point to be solved.The study of the benefit of the sponge city is not only related to how to locate and summarize the stage results of the sponge city construction in China,but also to influence the construction of the sponge city through the demonstration effect,which has a profound influence on the strategy adjustment and the strategy optimization of the construction of sponge city in the future.Therefore,we need to draw lessons from the advanced concepts abroad and combine with the experience of domestic development,and do some researches on the benefits of sponge cities.The low impact development technology is an important part of the sponge city.Therefore,this paper takes benefit of the low impact development facilities as the core,based on the LID facilities technology analysis and the rain flood model,and builds a quantitative index system based on the environmental benefits,economic benefits and social benefits.A sponge city construction project in Wuhan is taken as an example to analyze the comprehensive benefit of low impact development facilities.At first,the paper analyzes the pollution and emission reduction of four common LID facilities,such as green roof,permeable pavement,sunken green space and storage tanks.The comprehensive benefit model of low impact development facilities is constructed from three aspects include environmental benefit,economic benefit and social benefit by drawing on the system of the construction performance evaluation and assessment index put forward by the Ministry of Housing and Urban-Rural Development of the People's Republic od China.Also,some specific methods for the calculation are put forward.Secondly,model simulation is one of the most effective methods for scientific analysis of low impact development.Therefore,this paper studies the low impact development simulation system from the selection of the model,the model overview,the calculation principle of the rain flood model,the specific modeling process analysis and the parameter setting.Finally,through the case study of a Wuhan sponge city design project,the model is used to simulate the runoff reduction and the runoff peak reduction of the area in different ocasssion by using the rainstorm simulation system.The comprehensive benefit index system built is adopted to conduct the qualitative analysis.Quantitative analysis shows that the low impact development facilities have significant environmental benefits,economic benefits and social benefits.This research has initially established the index system of low impact development benefit quantifying,which provides an idea for the performance evaluation of the construction of the sponge city.The multifaceted positive effects of the construction of the sponge city also provide the economic support for its construction and investment,and promote the rapid development of the new model of rain and flood management in China.