Increasing risks related to landslides from degrading permafrost into new lakes in de-glaciating mountain ranges

• Main Authors: Haeberli, Wilfried, Schaub, Yvonne, Huggel, Christian
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2017
• Subjects: Institute of Geography; 910 Geography & travel; New Lakes; permafrost
• Online Access: https://www.zora.uzh.ch/id/eprint/127449/; https://www.zora.uzh.ch/id/eprint/127449/1/2016_Haeberli%20et%20al_16a.pdf; https://doi.org/10.5167/uzh-127449; https://doi.org/10.1016/j.geomorph.2016.02.009

While glacier volumes inmost coldmountain ranges rapidly decrease due to continued global warming, degradation of permafrost at altitudes above and below glaciers is much slower. As a consequence,many still existing glacier and permafrost landscapes probably transformwithin decades into new landscapes of bare bedrock, loose debris, sparse vegetation, numerous new lakes and steep slopes with slowly degrading permafrost. These new landscapes are likely to persist for centuries if not millennia to come. During variable but mostly extended future time periods, such new landscapes will be characterized by pronounced disequilibria within their geo- and ecosystems. This especially involves long-term stability reduction of steep/icy mountain slopes as a slow and delayed reaction to stress redistribution following de-buttressing by vanishing glaciers and to changes in mechanical strength and hydraulic permeability caused by permafrost degradation. Thereby, the probability of far-reaching floodwaves fromlargemassmovements into lakes systematically increases with the formation of many new lakes and systems of lakes in close neighborhood to, or even directly at the foot of, so-affected slopes. Results of recent studies in the Swiss Alps are reviewed and complemented with examples from the Cordillera Blanca in Peru and the Mount Everest region in Nepal. Hot spots of future hazards frompotential flood waves caused by large rock falls into new lakes can already now be recognized. To this end, integrated spatial information on glacier/permafrost evolution and lake formation can be used together with scenario-based models for rapid mass movements, impact waves and flood propagation. The resulting information must then be combined with exposure and vulnerability considerations related to settlements and infrastructure. This enables timely planning of risk reduction options. Such risk reduction options consist of two components: Mitigation of hazards, which in the present context are due to effects from climate change, and ...