Rainstorm-induced flood risks exacerbated in future by dual climatic-human impacts in the lower yellow river basin of China

Human-induced warming is intensifying the water cycle, increasing the risk of extreme precipitation and rainstorm-induced floods (RIF), posing a challenge for the sustainable socioeconomic development of the Yellow River Basin (YRB). Future flood risks under the dual impact of climate change and urbanization are less than adequately understood. In this study, we selected 9 indicators to formulate an RIF risk evaluation Model based on hazard of disaster-inducing factors, sensitivity of disaster-prone environment, and vulnerability of disaster-bearing areas (HSVM). We combined the analytical hierarchy process (AHP) and the entropy weight (EW) method to estimate RIF risks during historical (1950–2014), near-term (2021–2040), mid-term (2041–2060), and long-term (2081–2100) periods over the YRB under the SSP245, SSP585 scenarios. We found decreasing RIF hazard along the southeast to northwest direction, and moderate and high RIF hazard in the middle and lower YRB. Using the RIF risk during the historical period as the baseline, the RIF hazard increased by 8.34%-18.29% (11.66%-28.93%) from near to long term under the SSP245 (SSP585) scenarios. High vulnerability was identified in the middle and lower YRB, particularly over urbanized regions. Compared to the historical period, the vulnerability increased by 30.46%-79.39% (29.14%-93.18%) from near to long term under the SSP245 (SSP585) scenarios. Specifically, the RIF risks were precipitously high in the provinces of the middle and lower YRB, such as Shandong, Henan, and Shaanxi, and the RIF risk increased by 47.00%-91.50% (50.67%-169.51%) from near to long term under the SSP245 (SSP585) scenarios in the YRB. The increase in RIF risk over Henan and Shandong reached 58.02%-283.05% at different times under different scenarios in the future, which is higher than the historical levels of other provinces during the same period. This study highlighted RIF risks in the middle and lower YPR, calling for urgent mitigation measures for flood disaster reduction.