Construction And Application Of Sponge City Assessment System

As a feedback mechanism,the sponge-city evaluation can effectively reflect the performance and shortcomings of the construction,which give it a vital role in improving the effects of the sponge city construction.However,given the fact that the current evaluation for sponge city construction focuses on engineering assessment and lacks evaluation methods based on multi-technology system optimization,this study,considering the diversity and complexity of sponge city construction technology,put forward the concept of "eco-sponge elasticity".On this basis,the quantitative evaluation of eco-sponge elasticity,the elasticity cost-effective analysis,as well as comprehensive assessment of efficiency were carried out.Furthermore,the application study was carried out in Xiamen as an example.The conclusions are as follows:First of all,by summarizing the theoretical research of the sponge city and the studies of cities elasticity,this study puts forward the concept of "eco-sponge elasticity"It is composed of two parts,one is eco-elasticity and the other sponge-elasticity,the former means the extent of the adjustment and recovery resilience deriving from those natural or semi-natural eco-systems,and the later means that of the sponge-like resilience of water absorption and releasement deriving from urban constructed infrastructures under a certain stress of water environment condition.Among them,the sponge elasticity is composed of infiltration elasticity,storage elasticity,detention elasticity,transportation elasticity and decontamination elasticity.The ecological elasticity is composed of vegetation ecological elasticity and natural water ecological elasticity.Based on this,this study attempts to establish a connection with water function and propose a relevant elasticity evaluation framework to evaluate the characteristics of the water system.Secondly,on the basis of eco-sponge elasticity,this study calculates the cost-effective ratio of each elasticity,and evaluate the investment benefits in sponge city construction from the economic point of view.Then,combining the concept of "ecological sponge elasticity" and the elasticity evaluation and elasticity cost-effective analysis,this study,from the micro level,forms the an index system to evaluate the eco-sponge elasticity efficiency based on sponge elasticity efficiency,ecological elasticity efficiency and elasticity cost-effective analysis,covering 22 specific indicators in 9 items:infiltration efficiency,storage efficiency,detention efficiency,transportation efficiency,decontamination efficiency,rationality of green space ecological structure,green space ecological function,Natural water ecological function and elasticity cost-effective ratio.The indicators are classified into four grades according to the ecological sponge elasticity efficiency score,which respectively represents excellent(Ⅰ),good(Ⅱ),medium(Ⅲ),and poor(Ⅳ)to the eco-sponge elasticity efficiency.Lastly,this study uses the above evaluation framework,elasticity cost-effective analysis method,and the eco-sponge elasticity efficiency evaluation index system to evaluate the water system characteristics,investment benefits and eco-sponge elasticity efficiency of the six sponge city construction projects in Xiamen.The eco-sponge elasticity calculation and evaluation results show that the eco-sponge elasticity values rank as M1(156.73 mm)>X2(141.71 mm)>X1(110.25 mm)>X3(103.20 mm)>X4(156.73 mm)>M2(66.47 mm).Analyzing the elasticity one-by-one shows that Points X1,X2 and X3 have both good sponge and ecological elasticity,Point Ml has good sponge elasticity,Point M2 has good ecological elasticity,and Point X4 has both lower sponge and ecological elasticity.According to the analysis of the water function of each point region based on each’s elasticity value,it is found that the water resources,water environment,water safety and water ecological functions of the six sponge city construction projects are not balanced,and it is necessary to carry out targeted improvement and promotion according to the specific conditions of each region.The results of elasticity cost-effective analysis show that,the range of elasticity cost-effectiveness ratios of six sponge city construction proj ects is from 0.100 yuan/mm to 847.683 yuan/mm.Among them,the sponge elasticity cost-effective ratio varies from 0.100 yuan/mm to 2.892 yuan/mm,and the ecological elasticity cost is relatively high,from 44.960 yuan/mm to 847.683yuan/mm varies.As a whole,the ecological elasticitycost-effective ratio is much higher than the sponge elasticity cost-effective ratio.And for all the sponge elasticity cost-effective ratios,the cost-effective ratios of the infiltration elasticity and decontamination elasticity are equi.valent and in a relatively high proportion,which means that by optimizing the infiltration and decontamination technology combination,the construction cost of the sponge city can be reduced and the overall investment benefits can be improved.Specifically,Points X1,X3,M2 have both high infiltration and decontamination elasticity cost-effective ratios,and should be classify as key projects to improve.The results of eco-sponge elasticity efficiency evaluation shows that the eco-sponge elasticity efficiency of the 6 sponge city construction projects is different,and the order is X2(0.8260,Ⅰ)>X3(0.6620,Ⅱ)>M2(0.6008,Ⅱ)>X1(0.5923,Ⅲ)>M1(0.5802,Ⅲ)>X4(0.4373,Ⅲ).Specifically,Point X1 and X3 have a higher construction cost.Although the investment cost is lower at Point M1 and M2,the construction effect there is poor.Point X4 has poor runoff control,ecological and investment benefits,and its overall efficiency is low,which indicates that the sponge city construction project needs to be continuously improved.These results provides a new thought for the evaluation of a sponge city construction’s effect,further enriches and expands the study of sponge city.