Abstract High‐mountain environments are increasingly susceptible to cascading hazards such as rock avalanches and debris flows, particularly in the context of climate change. These processes often interact with water bodies and basal materials, amplifying their impact. On 12 May 2023, a ca. 0.2 Mm 3 rock avalanche initiated from the northern peak of Mt Job transformed into a supraglacial debris flow that travelled approximately 4.5 km down the valley and yield H/L ratio of 0.31. Job Valley, part of the Mount Meager Volcanic Complex (MMVC), has been a source of multiple landslides in the past, forming a large north‐facing amphitheatre now occupied by the Job Glacier. This study investigates the dynamics and governing processes of the event by leveraging photogrammetry, remote sensing, in‐field instrumentation data and numerical modelling tools. The volcanic rocks of Mt Job and the broader MMVC are hydrothermally altered, so the potential role of discontinuities in the failure mechanics of the rock avalanche is unclear. The rock mass in these steep slopes is under progressive deformation due to glacial debutressing, hydrothermal flow manifested by fumaroles, and snowmelt, causing effective stress redistributions. In the context of the climate change, the local temperature records show anomalous rises prior to the event, which may have caused rapid snow melt resulting in elevated water pressures, triggering the slope failure. A conceptual model serves to identify potential processes and causes and was used as a basis for numerical simulation of the debris flow. Using the multiphase r.avaflow model, we simulate the flow under two scenarios: a single‐phase solid flow and a multiphase flow incorporating basal snow entrainment and frictional melting to understand the processes that could have played a role for such a large runout distance given a small magnitude initial event. The findings underscore the importance of studying critical high mountains due to increasingly frequent hazards and reinforce the link between climate anomalies and slope instability process chains, where even a small event can impact significantly larger area.
Singh et al. (2026) studied this question.