Quantitative assessment of multi-scenario high-elevation and long-runout debris flow hazard and risk: a case study of Cuojiu Valley, south-eastern Qinghai-Tibet Plateau

In recent years, the impacts of climate change have significantly heightened the susceptibility of the Xizang Autonomous Region in China to various geological hazards. These hazards pose significant long-term implications for the development and maintenance of critical line projects in the vicinity. Consequently, the implementation of an effective quantitative assessment method for geological hazards becomes paramount for disaster prevention and mitigation. This study introduces a novel method integrating remote sensing, drone-based oblique photogrammetry, and onsite field investigation for effectively identifying geological hazards, and presents a risk quantification technique tailored for high mountain regions under varied rainfall possibilities. By utilizing this innovative approach, a comprehensive investigation was conducted to assess the characteristics and impacts of rainfall-induced debris flow in the Cuojiu Valley, southeastern Qinghai-Tibet Plateau, China, under varying rainfall probabilities. The study examines the effects of these debris flow on the regional line project, based on the maximum accumulated thickness and the highest affected height triggered by rainfall. The analysis revealed that severe rainfall events act as triggers for these hazardous occurrences. Importantly, the study highlights that the safety of critical line projects in the region is compromised by the identified debris flow risk in the Cuojiu Valley during extreme rainfall events. This study’s novelty lies in identifying the distribution of geological hazard sources through the proposed method and conducting a quantitative assessment of multi-scenario high-elevation and long-runout debris flows in the Cuojiu Valley. This provides valuable insights for preventing geological hazards in high-elevation valleys.