Tipping points in urban growth: How urbanization reshapes flood resilience and social vulnerability in China.

Urbanization is often portrayed as either a pathway to progress or a process that could amplify disaster risk. Yet, its true influence lies in how it reshapes resilience to hazards and the vulnerability of people most at risk. Using provincial data from China (2006-2020), we integrate urbanization, flood resilience, and social vulnerability into a unified framework to examine their coupled evolution. We find that rapid urbanization is a double-edged process: while it initially increases exposure, grouped cross-provincial analysis reveals a transition suggestive of a tipping point at the aggregate level, with social vulnerability declining sharply and resilience accelerating once the urbanization level enters a higher development stage (urbanization level > 0.75). Regional trajectories diverge, with provinces like Gansu trapped in vulnerability, Guangdong achieving resilience leaps, and Shanghai consolidating a high-level balance. Nationally, the coordination among the three systems rose by 83%, yet disparities persisted, particularly in western and northeastern regions. These findings show that the design of urban growth-not its pace alone-determines whether cities amplify or mitigate climate-driven flood risks, with lessons extending far beyond China.