Assessing the scale effect of urban vertical patterns on urban waterlogging: An empirical study in Shenzhen

Waterlogging disasters seriously affect residents' lives. Investigating the factors affecting waterlogging is crucial for mitigating waterlogging. Although waterlogging is closely related to land-use patterns, most of the previous studies have analyzed only the impact of urban horizontal patterns on waterlogging at a single scale. Few studies have focused on the role of urban vertical patterns from a multiscale perspective. Therefore, this study investigated the influence of various factors on the density of waterlogging points at grid scales of 1-5 km using Pearson correlation analysis and the random forest model. We conducted a case study for Shenzhen City, and the results show that the building coverage ratio, building crowding degree, building density, proportion of impervious surfaces, proportion of green space, and population density are the most important factors. Moreover, the urban horizontal and vertical patterns have significant scale effects on waterlogging. The influence of horizontal patterns on waterlogging is maximum at a scale of 3 km, while the influence and dominance of the vertical patterns increase with scale. Therefore, controlling building congestion is necessary for alleviating waterlogging, and the rational planning of urban horizontal and vertical patterns is important for the construction of sponge cities. Our results provide decision support for urban land-use optimization and waterlogging mitigation, thereby facilitating sustainable environmental management.