Evaluating the runoff storage supply-demand structure of green infrastructure for urban flood management

Rapid urbanization has resulted in an increase in impervious surfaces and a decrease in green infrastructure (GI), changing the process of the regional hydrological cycle, coupled with climate change, which is expected to increase the frequency and magnitude of urban floods resulting from extreme events in the city. GI can provide crucial stormwater regulation functions to help cities mitigate the increased stormwater runoff and related flood risks. This study presents a method to assess the runoff storage supply-demand structure of green infrastructure in the Shenyang urban area. The runoff storage supply of GI was calculated by rainfall and the maximum rainwater storage capacities of the canopy and soil. The runoff storage demand was estimated by the direct runoff and discharge capacity of the drainage pipe network. The runoff storage supply-demand structure was analyzed using a supply-demand index designed based on the supply-demand balance of runoff storage capacity. The results showed that large and contiguous areas of runoff storage supply are mainly concentrated in the north, southwest and southeast and are mainly distributed in the suburbs of Shenyang. The runoff storage supply in the center of Shenyang is limited and seriously fragmented. The runoff storage demand of the urban center is markedly higher than that of the peripheral suburban areas. With the increase in rainfall, the supply of runoff storage decreases, while the demand for runoff storage increases, resulting in the runoff storage supply gradually being unable to meet the demand. For different urban functional zones (UFZs), only the supply-demand balances of green space were positive under 78 mm rainfall (return period of 50 years) conditions, and those of other types of UFZs were negative, revealing that the runoff storage supplies of most UFZs were imbalanced. The method can help identify the runoff storage supply and demand of each catchment and further provide the possibility of interregional runoff storage capacity sharing or allocation. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

Rapid urbanization has reduced green infrastructure and increased urban flood risks. A study evaluating the runoff storage supply-demand structure in Shenyang found limited and fragmented runoff storage supply in the city center, with significantly higher demand compared to suburban areas. As rainfall increases, the supply decreases and demand rises, challenging the balance between supply and demand.