ASSESSMENT OF THE FLOOD CONTROL CAPACITY AND COST EFFICIENCY OF SPONGE CITY CONSTRUCTION IN MIANYANG CITY, CHINA

Abstract

 To prevent flooding in urban areas, the Chinese government launched the “sponge city” program, which is similar to the low impact development (LIDs) approach. However, the flood control capacity and cost efficiency of sponge cities in China have not been well studied, especially for city-scale urban area. Cost efficiency is an important consideration for local governments implementing sponge cities.

 The objective of this study is to quantify the utility of sponge city construction for urban flood control, based on a rainfall-runoff simulation using the Storm Water Management Model (SWMM). The cost efficiency of LIDs used in sponge city construction is also evaluated. Mianyang City, located in the southwestern part of China, was the study area. The results showed that the four types of LIDs (green roofs [GRs], permeable pavement [PP], rain gardens [RGs] and rain barrels [RBs]) effectively reduced the peak flow (23.0-30.4%) and total flood volume (24.9-29.2%) for nine flood events in 2015 and 2016. Different intensities (return periods) of precipitation have been analyzed to assess the flood reduction achieved through the installation of LIDs. For return periods of 2, 5, 10, 20, 50, and 100 years, the peak flow and flood volume reduction rates were 11.7-28.5% and 14.8-29.9%, respectively; these rates were lower in cases of more severe precipitation. The cost efficiency analysis showed that RGs are more cost efficient than other LIDs.