Impacts of climate change on debris flow occurrence in the Cordillera of Western Canada and the European Alps

The impacts of recent and continuing climate change on terrestrial systems are still debated. Evidence is mounting that climate change is affecting the stability of slopes, although the full extent, time, and magnitude of the response remain uncertain, in part because climate is only one of the factors contributing to slope instability. Moreover, the magnitude and character of climate change can differ considerably both regionally and locally. Nevertheless, mountain environments respond rapidly to climate warming, in part because of the presence of glaciers and permafrost. The paper contributes to discussions within the scientific community of the impacts of climate change on mountain environments by discussing controls on debris flow occurrence in the Cordillera of western Canada and the European Alps. Several case studies illustrate how cryosphere degradation can play a significant role in debris flow occurrence in glacial and periglacial areas, both on short and on long time scales. Processes responsible for debris flow occurrence in a warming climate include rock falls and rockslides induced by glacier debuttressing, thaw of alpine permafrost, sudden draining of glacial lakes, and exposure of unconsolidated, unvegetated, and commonly ice-cored sediments during glacier recession.