4.3 Urban planning implications
Our results can provide guidance to optimize urban morphology for urban flooding risk management. This study emphasize that land cover configuration was the dominant factor influencing the urban flooding. Therefore, it is necessary and important to properly allocate urban components (e.g., impervious surfaces, green space, and waterbody). As terms of the land use cover, with urban green space decreased and fragmented, rainwater runoff reduction rate decreased from 23% to 17% during the period 2000 to 2010 in Beijing (Zhang et al., 2015). Decreasing impervious surfaces and increasing urban green-blue spaces were beneficial for mitigating the urban flooding risks dramatically.
3D building patterns also have a certain impact on urban flooding. It is a good choice to control the floor area ratio under given 3D fractal. In generally, urban planners restrict building height strictly in Beijing. Buildings induced rainfall redistribution is expected to increase the peak flow and become more important with the increase of rainfall intensity (Cao et al., 2021). Thus, slowing down the building coverage ratio became another choice. In practice, green roofs were beneficial for urban stormwater regulation, and the runoff mitigation capacity varied with the spatial variability of green roofs and greening on effective roof surfaces in small urbanized catchments in Beijing (Yao et al., 2020). Additionally, 3D building landscape alters microclimate and changes rainfall pattern.