Green infrastructure refers to vegetation covered areas such as parks, lawns, residential gardens, and roadside flowerbeds in cities, which have important water-related functions such as reducing rainfall runoff, improving water quality, and maintaining regional water cycle. Due to the scarcity of urban land, a large amount of green space has been transformed into residential and commercial land, resulting in a reduction in the area of green infrastructure, and the fragmentation of vegetation patches, thus making urban runoff regulation and storage capacity insufficient. The intensification of urbanization has caused increasing pressure on the runoff storage capacity of green infrastructure, while the supply-demand imbalance of runoff storage will further aggravate urban waterlogging. 

To address this issue, associate Prof. Li Chunlin and Prof. Liu Miao of the Landscape Ecology Group of the Institute of Applied Ecology (IAE), Chinese Academy of Sciences took the urban area within the third ring road of Shenyang as the research area, evaluated the runoff storage of urban green infrastructure and its supply-demand balance and spatial characteristics by calculating the canopy interception and soil infiltration capacity, building runoff models, and calculating supply-demand index.  

The scientists found that the large-scale, contiguous runoff storage and replenishment areas are mainly concentrated in the suburbs of the city. The supply capacity of runoff storage in the downtown city is limited and severely dispersed, while the demand for runoff storage is significantly higher than in the suburbs and peripheral areas of the city. With the increase of rainfall, the supply of runoff storage decreases, while the demand increases, resulting in that the supply of runoff storage can not meet the demand gradually. The gap between the supply and the demand is the largest within the first ring road area where is comprised of high-density residential and commercial buildings; and this area is a key area where urban waterlogging occurs.  

Through the analysis of the supply and demand structure, it can be inferred that the catchment with a supply-demand index less than - 0.4 is a high risk area of waterlogging. This method is helpful to evaluate the runoff storage capacity of urban catchments, and provides a scientific method for alleviating urban waterlogging and improving the inter-regional supply-demand structure of runoff storage. 

This study was published in Journal of Cleaner Production under the title "Evaluating the runoff storage supply-demand structure of green infrastructure for urban flood management".  

The research was supported by the National Natural Science Foundation of China.