La lave torrentielle du 24 août 2015 (Lanslevillars, Savoie) : un cas de dégradation du pergélisol dans le contexte du réchauffement climatique ? Étude de l'évolution des dynamiques du glacier-rocheux du col du Lou entre 1970 et 2016 : approche par photogrammétrie

• Main Author: Ribeyre, Charles
• Other Authors: Université Grenoble Alpes - Institut de géographie alpine (UGA IGA), Université Grenoble Alpes 2016-2019 (UGA 2016-2019 ), Philippe Schoeneich
• Format: Thesis
• Language: French
• Published: HAL CCSD 2016
• Subjects: Photogrammetry; Rock glacier; Glacier-rocheux; Photogrammétrie; geo; envir; permafrost; pergélisol
• Online Access: https://dumas.ccsd.cnrs.fr/dumas-01520648/file/Ribeyre_Charles.pdf; https://dumas.ccsd.cnrs.fr/dumas-01520648

On August 14th 2015, a storm took place on the Grand Mont Cenis Mountain (3377 m) and two significant landslides. The two landslides detached from the frontal area of a rock-glacier situated downstream of the Lou pass at a height of 2800 mind originated two consecutive debris flows that out broke in the downstream of Lanslevillard (Haute Maurienne, Savoie), bringing enormous masses of debris into town and causing thousands of euros worth of damage. Since the storm’s magnitude was not big enough to cause a phenomenon of this scale, it became interesting to look at the role that permafrost might have in this situation. Indeed, the Alps have not remained unaffected by the globally recognized increase in atmospheric temperatures, where a rise from 0.5 to 1°C has been measured within the last decades. This temperature increase brought a real morphogenic crisis in the lower limit of the permafrost belt. Numerous studies have shown a correlation between temperature rises and an increase of the dynamics of rock-glacier these past few years. In the context of favorable topographic conditions (steep slopes) these dynamic changes can lead to a rise of certain gravitational phenomena (ruptures, debris flows). Our study fits into this context of the correlation between the degradation of permafrost and global warming and its potential hazardous consequences. The objective of the study is to determine if the debris flows that occurred in August 14th could be explained by a degradation of permafrost caused by global warming at the site of the Lou pass. For this study we studied the development of the landslide at Lou pass by comparing the orthophotos and MNT generated by photogrammetry, starting with aerial images of IGN dating back to 1970 up until recent photos. Le 14 août 2015, un orage sur le signal du Grand Mont Cenis (3377 m) génère deux importants glissements de terrain. Les niches d’arrachement de ces deux glissements se situent au niveau du front d’un glacier-rocheux situé juste en aval du col du Lou vers 2800m ...