Optimizing Urban Green Space Layouts for Stormwater Runoff Treatment in Residential Areas: A Case Study in Tianjin, China

Abstract

Residential areas comprise more than 30% of the urban built-up zones of China. High-density residential areas and high proportions of impervious surfaces make residential areas prone to severe flooding. Low-impact development practices are broadly applied to solve these problems, and as a main component of low-impact development practices, green spaces have also drawn attention because of their capacity to control rainwater. However, the effects of green space spatial characteristics on hydrological processes have been overlooked. In this study, to determine how to optimize the layout of the green space system to improve the capacity of stormwater management, data from Tianjin were analyzed using a FRAGSTATs model and a SWMM model to identify how the layout of green spaces affects the process of rainwater generation and concentration in terms of three typical residential area layouts. The results show that (1) when it is possible to increase the amount of green space, maintaining a high patch density is the best way to achieve runoff treatment; (2) when newly built green space is limited, increasing connectivity between existing green spaces is the best way to control rainwater, especially in enclosed and axial modes; (3) when comparing the efficiency of the three modes, the axial mode presents the best performance in terms of promotion rate. These results will provide those developing urban residential areas with more economical, practical, and suitable layout strategies for green space systems in terms of planning, design, and optimization aimed at stormwater management.