Intensive population exposure in urban waterlogging-prone areas: From the perspective of spatial continuum of the urban environmental system

Abstract

Urban waterlogging is increasingly recognized as a systemic risk rooted in the degradation of urban environmental systems. While existing research has predominantly focused on inundation probability and depth, the systemic vulnerability and spatial patterns underlying waterlogging dynamics remain poorly understood. Taking Shenzhen as a case, this research develops a three-tiered spatial framework that links historical inundation spots to slow-changing biophysical processes. The waterlogging-prone areas and spatial continuums are further delineated to explore the spatial-demographic exposure patterns. Results show that portions of the urban environmental system are undergoing unsustainable processes, evidenced by significant decline in key biophysical variables. These variables exhibit threshold-governed behavior, declining sharply within approximately 1.4 km radius of inundation points before stabilizing asymptotically farther away. Within the delineated waterlogging-prone areas, 67 high-risk spatial continuums were mapped. Although these continuums contain 20-21 % of the total population, they experienced a disproportionate 65.9 % surge in population density between 2006 and 2016. The findings indicate that the urban environmental system has entered a vulnerable, waterlogging-prone state in certain regions. Given the spatial overlap of high-risk waterlogging with dense population clusters, targeted adaptation strategies and regulatory interventions are urgently needed.