Multiscale watershed landscape infrastructure: Integrated system design for sponge city development

Conventional centralized drainage systems are not only expensive, but their mono-function to discharge surface runoff also imposes a negative effect on the local environment while compounding regional watershed dysfunction. Sponge city initiative promoted by the Chinese government is a broader sustainable stormwater management concept that aims to use more nature-based solutions, reduce urban flooding and runoff pollution, and increase rainwater resource usage. As part of decentralized and cost-effective solutions, green infrastructure (GI) is considered in the Sponge City development across China. Although GI has been successfully implemented through a range of small-scale projects, the GI approach has not been adopted widely, which is because the GI approach is micro-scale techniques and the local government is skeptical about the efficiency of GI to mitigate stormwater on a large scale. Although some researchers have explored the effectiveness of GI to reduce stormwater in small catchments, only a limited number of studies have examined the efficacy of GI at the watershed scale. Moreover, there is lack of a system and cross-scale approach in sponge city practices. To understand the effect of GI on the watershed scale, this paper proposed a comprehensive approach using ArcGIS and SWMM platforms to study the spatial configuration and implementation of multi-scale stormwater management. The approach is to apply a three-step sequence of catchments, sub-catchments, and micro-catchments for the urban watershed through designing interconnected network of landscape infrastructure (LI) systems. The design scenarios and performance of LI system-based approach with different combinations and sizes of the sponge facilities were analyzed based on the Old Town district of Hefei City, China. This study demonstrated that the inherent capacity of the landscape can act as the conduit for multifunctional, flexible, localized, and synergistic infrastructural systems, in which cross watershed holds promise to decrease both runoff volumes and peak flows while providing ecosystem services, such as enhancing neighborhood aesthetics and cultural/health benefits through shared public green spaces. Thus, Sponge City Development here as green concepts and techniques for nature-based solutions enhances the function and value of green infrastructure with benefits of ecological, economic and social significances, which presents a new approach for sustainable city making.