Abstract Debris‐flow disasters triggered by extreme rainfall have posted high risks in mountainous areas. However, the hazard of potential debris flows remains difficult to assess given the context of climate change. For this purpose, a novel quantitative framework for assessing the impact of climate change on debris flow hazard was proposed in this study. It can indicate how the hazard degree of a debris flow will change with a changing climate over different periods. The Changzhoucun (CZC) debris flow hazard in Tianjin of north China was selected as a case study. We analysed the evolution trends of extreme rainfall events versus time windows based on rain gauge data from 1951 to 2017. Four distribution functions were examined and compared, thus defining four different rainfall scenarios (full history, far history, mid history, near history). A physically‐based model named FSLAM was employed to compute stability in initiation areas and peak discharge in the channel. The FLO‐2D code was applied to simulate runout characteristics of the debris flow to conduct hazard mapping. We observed an increase in the extreme rainfall frequency in the summers of the region. The near history presented the largest rainfall level, whereas the full history was the smallest. Under the return period of 20 years, the projected difference in 48 h extreme rainfall and runoff between full history and near history reached 4.4% and 5.4%, respectively. In addition, the debris flow magnitude, characterized by depth, velocity and impact force, was also projected to increase, but these changes were unevenly distributed throughout the catchment. The results can contribute to better predicting debris flow development at catchment scales and provide a basis for the government to identify and manage high‐risk areas.
Guo et al. (2026) studied this question.