Construction And Application Of Sponge City Assessment System

Under the background of rapid urbanization,owning to constant expansion of urban area and unreasonable planning,urban underlying surface has been changed dramatically;a great quantity of lakes,rivers,wetland and green land are grabbed;urban impermeable area increases.Therefore,urban hydrological cycle is damaged,leading to a series of urban water problems,which is mainly presented in several aspects:shortage of water resources,deterioration of water environment,frequent occurrence of flood,degeneration of water ecosystem.Based on current situation of urbanization and advanced management experience of rainwater from abroad,China proposed a model of construction for sponge city.?The technical manual for the building of sponge city-low impact development(trial))),issued by Ministry of Housing and Urban-rural Development of the People's Republic of China in 2014,aimed at enhancing urban flexibility to respond to environmental changes and natural disaster by utilizing natural drainage system and establishing ecological drainage facility.In 2015,?Performance evaluation and assessment method for the construction of sponge city?was published,providing an effective guidance for constructing a sponge city.However,since China enjoys a vast territory,making climatic conditions and water problems in different areas various,the construction of sponge city and index system should reflect regional difference.This paper,based on the existing evaluation index of sponge city from foreign countries,establishes a assessment index system for sponge city according to regional difference.Firstly,the scope of this article is defined,that is,taking monsoon area above 400mm isohyetal line as research area and 800mm isohyetal line as limitation.Thus,research areas were divided into northern rainless area and southern pluvial area.On the foundation of profound analysis of the concept and connotation of sponge city,the evaluation index from 20 sponge cities were initially identified.Questionnaire were designed to assess the index of preliminary screening;software SPSS was adopted to conduct factor analysis on the result of questionnaire;software AMOS was utilized to make confirmatory factor analysis.Consequence indicated that:17 evaluation indexes were identified in southern pluvial area;18 in northern rainless area;excessive indexes were the change rates of underground water level.For factor analysis,the indexes from two areas were divided into 4 categories.In accordance with the meaning of indexes,they were named as water security,water environment,water ecology,water resources.Water surface ratio and annual total amount of run off control rate had different results in various areas.Water surface ratio was respectively regraded as water ecology and water security in northern rainless area and southern pluvial area;annual volume-based control rate belonged to water resources and water environment.In the stage of confirmatory factor analysis,the difference of two areas was mainly reflected in the difference of weighting coefficient of water resources and water security.In northern rainless area,the weighting coefficient of water resources was apparently higher than other categories,while in southern pluvial area,the weighting coefficient of water security was the highest,reflecting the key point of sponge city in different areas.Then,assessment index systems of sponge city in northern rainless area and southern pluvial area established in phrase of empirical analysis were applied respectively in Beijing and Shanghai.Results showed that the construction was at a low level;impervious surface rate,ecological slope rate,landscape connectivity,Drainage project compliance rate and sunken green space rate were relatively low;there was clear difference in water surface ratio,rainfall retention rate,rainwater utilization rate and reclaimed water reuse rate in both cities,and its difference was in conformity to the discrepancy of index system,thus proving the reasonability of the system.In the end,on the basis of assessment result of empirical analysis,advanced experience from abroad,and deficiencies of domestic laws,regulations as well as urban planning,some measures and suggestions about the construction of sponge city were proposed.The research in this paper improves assessment index system of sponge city in different areas and pertinence of the construction of sponge city,which can provide certain guidance for the construction of sponge city in various regions.