Study on Planning and Design of Blue-Green-Gray Transformation of Lakeside Cities to Deal with the Complex Urban Waterlogging Caused by Extreme Rainstorm

Some lakeside cities may suffer from urban waterlogging owing to the backwater effect caused by the rise of lake water levels under a extreme rainfall scenario in the basin, but it is not suitable for large-scale gray drainage infrastructure upgrading in high-density lakeside urban built-up areas. This study, as per this, constructs the blue-green-gray infrastructure reconstruction planning and design mode to alleviate the waterlogging in the extreme rainstorm scenario of the lakeside city. Extending the Shiwuli River Basin in Hefei City, Anhui Province, China as an example, this study uses SWMM software to simulate the waterlogging situation in the study area under an extreme rainstorm under the urban planning scenario. According to the waterlogging situation, different hydrological scenarios (scenarios where the pipe network can and cannot discharge normally) are used to plan and design the blue-green-gray infrastructure reconstruction of the study area with both constructed land and non-constructed land. The research results show that just the planning and design of blue and green space can effectively reduce the degree of urban waterlogging, and with the cooperation of artificial pre-drainage, its own hydrological characteristics and geographical conditions can be used to prevent urban waterlogging caused by the backwater effects of a lake. In this study, the blue-green-gray transformation planning and design model of lakeside cities can deal with the complex urban waterlogging caused by extreme rainstorms, and the model could be extended to other cities along rivers or lakes with similar conditions.