Eco-Sponge Elasticity and its Indices Developed to Assess the Performance of Infrastructure in Sponge Cities:

Abstract

In recent years techniques for assessing the "sponge city" concept in practice have been developed and diversified at a rapid pace, therefore a unified assessment framework based on sponge techniques is becoming more and more important for comparing and analysing the performance of different techniques across different sponge city projects. However, previous work has mainly focused on enhancing or developing a certain single sponge technique. This research tries to establish a framework through integrating the resilience of the natural ecosystem with that of engineered infrastructure of sponge cities, forming a new concept of 'Eco-sponge resilience', and quantifying 'Ecosponge Elasticity'. In particular, a set of elasticities with a unified dimension are developed. The eco-sponge elasticity mainly consists of five types of sponge elasticity and two types of ecological elasticity, including factors such as infiltration, storage, detention, transportation and decontamination, ecological vegetation and natural ecological water elasticities, with which the value of eco-sponge elasticity of a sponge city project can be easily estimated. This research also considers a case study to interpret how to assess the ecosponge elasticities of six pilot sites of sponge city projects in Xiamen. The result shows that the presented evaluation method is feasible and helpful for assessing and enhancing the performance of sponge cities considering four aspects: the water environment, water resources, water security and water ecosystem of the urban system.