1. INTRODUCTION
Along with rapid urbanization, the proportion of world urban residents is expected to increase from 56.2% in 2020 to 67.2% in 2050 (DESA, 2018). It was estimated that global urban landscape area has increased by 19.1 million hm2 between 1985–2015, and approximately 70% of the newly urban landscape witnesses in Asia and North America (Liu et al., 2020). Unprecedented rate of global urbanization, whose most significant feature is the natural and semi natural surface being replaced by the impervious surface, causes a series of ecological challenges, such as urban flooding, urban heat islands, air pollution, and loss in natural habitat (Kulmala et al., 2020; Oke et al., 2017; Grimm et al., 2008; Foley et al., 2005). Urban flooding, refers to the fact that the heavy rainfalls overwhelm the capacity of self absorption and drainage pipelines drainage. Urban flooding causes great economic losses, and even kills the urban dwellers (Rentschler et al., 2022; Paprotny et al., 2018). It was reported that more than half of the world’s population was affected by flooding from 2010 to 2019. China suffered from the flooding with 400 events contemporaneous. Meanwhile, global warming is likely to exacerbate urban flooding risks (Touma et al., 2022; Debele et al., 2019). Thus, how to reduce urban flood loss is of great significance to urban sustainability. Fortunately, a series of practices have been conducted, such as “best management practices”, “low impact development”, and “sponge city construction” (Davis et al., 2005).
Urban flooding has attracted more and more attention for its frequent occurrence and severe damage (Kim et al., 2022; Lin et al., 2022; Ma et al., 2022; Chen et al., 2021; Sun et al., 2021; Yang et al., 2021; Paprotny et al., 2018). Previous related studies have tended to reveal urban hydrological mechanism by adopting field investigations, laboratory modeling and urban hydrological modeling (Ma et al., 2022; Shrestha et al., 2022; Li et al., 2022; Muthusamy et al., 2021). Among these, a comprehensive understanding of the spatial–temporal patterns of urban flooding and its most influencing factors was vital and fundamental (Steinhausen et al., 2022; Li et al., 2022). Urban flooding events were significantly clustered and mainly distributed in the central urban area (Li et al., 2022; Zhang et al., 2020). The distribution pattern of urban flooding events can be caused by topographic conditions (i.e., elevation, slope, roughness, and microtopography), rainfall intensity, land cover composition and configuration, stormwater storages, and drainage systems (Hettiarachchi et al., 2022; Li et al., 2022; Wang et al., 2022; Dumedah et al., 2021; Liang et al., 2021). For example, Tehrany et al. (2019) found that elevation was significantly impacted urban flooding in small catchments. When the digital elevation model resolution increased from 50 m to 1 m, flooding extent and mean flood depth decreased by 30% and 150%, respectively (Muthusamy et al., 2021). However, it is difficult to alter topographic and heavy rainfall, so more and more researches seek to mitigate urban flooding through rational urban planning. On the one hand, an improvement in urban drainage system was beneficial to manage urban runoff. On the other hand, optimal blue–green–grey spaces were also important to alter urban hydrological process and reduce flooding risks.
Numerous studies have shown that land cover and land configuration have direct effects on urban flooding in the horizontal (Hettiarachchi et al., 2022; Wang et al., 2022; Li et al., 2020). However, fewer studies have investigated the impact of buildings on urban flooding in the vertical dimensions (i.e., building height and its heterogeneity). Although buildings and roads may have roughly the same permeable capacity, their roles in regulating urban runoff can vary greatly (Cao et al., 2021). Specifically, building height and building coverage ratio alter runoff generation time. Building facades increase the surface contact with raindrops and thus decrease runoff. In addition, the interaction effect of building and its surrounding miniature garden has direct effects on the ground runoff. Furthermore, buildings alter its surrounding microclimate, which has direct or indirect effect on soil moisture and evapotranspiration. Thus, three-dimensional building pattern might change the local hydrological process. Lin et al. (2021) noted that adding building metrics can better explain the probability of flooding occurrence in Shenzhen, especially the building coverage ratio.
A large number of three-dimensional building metrics have been developed to comprehensively characterize building patterns (Kedron et al., 2019; Liu et al., 2017). A series of studies further explored the relationship between three-dimensional building pattern and land surface temperature/air temperature, air pollution. However, the effect of 2D/3D building patterns on urban flooding remains unclear. We attempt to address the following two questions: (1) how urban flooding events affected by 2D/3D building patterns in megacies? And (2) does an enhancement effect exist between 3D building metrics? Addressing these questions can promote our further understanding on the role of buildings in urban flooding. Such understanding can provide insights for urban flooding mitigation.