Exploring the Link Between Climate Change and Catastrophic Mass Movement Event Magnitude in High Mountain Regions

Catastrophic mass movements are dynamic processes that involve the rapid (>10m/s average velocity) down-slope movement of large volumes of rock and superficial deposits. This study aims to evaluate the factors that control the occurrence and dynamics of mass movement events in the high mountain cryosphere. Specifically, the mechanism of entrainment and bulking, and how these are being influenced by contemporary climate change. Bulking occurs when an event erodes and entrains surrounding material including debris, ice and water, to potentially increase an event volume and subsequent run out tenfold. The implications of flow bulking on hazard management are significant, but are under investigated in this field, especially in high mountain regions.

To better understand the bulking mechanism we must characterise the rheological evolution and sediment budget of mass movement events, and determine the topographical and landscape features (such as availability of water and entrainable sediment) which encourage bulking. To achieve this, we focussed on three contemporary mass movements in the Andes and Coast Mountains: 2017 Villa Santa Lucía, Chile, 2010 Q'wel'qw'elústen (Mount Meager), Canada, and 2019 Nsk`enú7 (Joffre Peak), Canada, using a combination of field investigations, numerical modelling, and remote sensing techniques. We have critically assessed the capacity of the Rapid Mass Movement Simulation model predict the behavior of catastrophic mass movements when entrainment is considered, validating these conclusions with field observations. These analyses highlight the interconnection between how increased glacial run-off, decline of permafrost, and glacial retreat, are affecting the behavior of such phenomena. By focusing on the bulking mechanism, we can improve forecasting of maximum inundation zones of future catastrophic mass movement hazards, potentially reducing the human and economic impacts of such events which are likely to become more frequent as a result of contemporary climate change.