Study On The Construction Of Sponge City In Xi`an

Xi’an is a city,which is influenced by the shortage of water resources and located in the northwest of the arid and semi-arid regions. Its soil is collapsible loess. With the development of urbanization in Xi’an, impermeable pavement area has increased significantly.Rainwater cannot drain timely, resulting in waterlogging. This paper presents the idea of the construction of the sponge city in Xi’an to solve the problems above.Sponge city uses low-impact development systems to keep the hydrologic characteristics of the site the same after the city was developed.In this way, rain runoff flow, peak flow, and runoff pollution can be reduced sufficiently. Low-impact development systems include many techniques, such as green roofs, split-flow device for roof initial rainwater,grass swale, permeable pavement, sunken greenbelt, wet ponds, constructed wetlands.This paper introduces the advanced technology and policy and the utilization of the rainwater at home and abroad, citing various outstanding cases of low-impact development systems. It describes the natural geographic, engineering geology and social conditions in Xi’an.In addition,it analyzes the water utilization structure and waterlogging phenomenon. Comparing the data of 2005~2013 years, it has the results of the average annual rainfall and characteristics of rainfall in Xi’an.Besides,it is necessary and significant to construct a sponge city in Xi’an.This paper presents some low-impact development techniques: the functions and applications of the green roofs, grass swale, permeable pavement, rain gardens, sunken greenbelt.It describes the other techniques of low-impact development systems briefly and compares different measures by analyzing the advantages and disadvantages of various low-impact development techniques. Two cases are listed basis to analyze different aspects of low-impact development techniques. Project cost savings are 764,400 yuan and 20,200 yuan respectively.In the end, this paper concludes that low-impact development systems can effectively reduce runoff flow, harvest rainwater effectively and alleviate urban waterlogging as well. At the same time, low-impact developmen systems have good economic, environmental and social benefits.