Mapping the capacity of concave green land in mitigating urban pluvial floods and its beneficiaries

Pluvial floods can exert significant pressure on urban sustainability and human wellbeing during rapid urbanization. Rapid urbanization and exacerbated flooding have stimulated investigations of green land's role in mitigating urban flooding in China. The newly applied Sponge City plan considers the concave green land (CGL) as an effective tool in mitigating pluvial floods. However, its capacity and beneficiaries still need to be elucidated. This paper fills this research gap by integrating urban flood simulation, scenario analysis, and mitigation assessment in central Shanghai, China. It reveals that CGL could not only mitigate direct runoff and inundation, but also reduce population exposure and enhance community resilience. CGL with a depth of 0.10-0.20 m can mitigate direct runoffs by 23.63-98.35% and inundation extents by 26.09-82.41%, resulting in a slide of the exposed urban population by 0.40-1.04 million persons and the exposed elders by 0.04-0.12 million persons. Moreover, the effectiveness of CGL varies spatially implying for a sound spatial planning of CGLs and a potential combination with other flood mitigation measures. These findings could help cities particularly in developing countries to adapt to rising pluvial flooding through urban planning and nature-based flood mitigation measures.