Growing population exposure to extreme floods in the Pearl River Basin in the future under global warming levels

Climate change and socioeconomic development are projected to change flood risk in China’s Pearl River Basin (PRB), yet the future pathways of this risk remain unclear. This study quantifies population exposure to extreme floods from 1985 to 2100 by integrating a basin-calibrated WEB-DHM-SG hydrological model with bias-corrected ISIMIP3b climate projections and Shared Socioeconomic Pathway (SSP126, SSP370, SSP585) population datasets. We assess exposure at global warming thresholds from 1.5 °C to 4.5 °C and decompose the contributions of climatic versus demographic drivers. Results indicate that population exposure peaks around mid-century at approximately 20 million people across all scenarios, then diverges: it declines under SSP126 (to ∼ 18 million), rises under SSP370 (to ∼ 22.5 million), and stabilizes under SSP585 (near ∼ 20 million). Sensitivity analysis reveals that each additional half-degree of warming increases the exposed population by ∼ 2.8 × 10 5 (1.8 %) and raises the exposure share by ∼ 0.36 %. Climate change drives approximately 80 % of the basin-wide exposure increase, while local population dynamics—particularly in the Pearl River Delta—account for over one-fifth of the rise above 3 °C. The Dongjiang River and lower Xijiang River are identified as persistent hotspots, whereas sections of the Beijiang River exhibit relative resilience. These findings underscore the necessity of low-emission pathways and risk-informed adaptation strategies to mitigate future exposure.