Retro-trajectoires du risque avalancheux résultant de changements climatiques et sociaux-environnementaux sur des sites choisis des Alpes françaises

par Taline Zgheib

Projet de thèse en Sciences de la Terre et de l'Univers et de l'Environnement

Sous la direction de Nicolas Eckert et de Samuel Morin.

Thèses en préparation à Grenoble Alpes , dans le cadre de Terre, Univers, Environnement , en partenariat avec IRSTEA Grenoble (laboratoire) depuis le 01-10-2017 .

  • Résumé

    Modélisation numérico-probabiliste des avalanche sur le temps long (échelle de 2 siècles),prenant en compte les variations du climat et des pratiques sociales.

  • Titre traduit

    Backward trajectories of avalanche risk resulting from climatic and socio-environmental changes on selected hot spots of the French Alps.

  • Résumé

    Long term changes in snow avalanche risk result from combined changes in its environmental (climate, forest ecosystems) and social (land use, social practices, tourism, etc.) components. In reverse, changes in avalanche risk finely traduce the rapid evolution of a sensitive system. Combining tree-ring reconstitutions, historical archives and instrumental data and analyzing these using advanced statistical tools may improve our knowledge and understanding of these changes. As a contribution to this effort, this PhD will fill the gap between fully empirical approaches and more physically based numerical simulation tools already working in the stationary case. Specifically, a statistical numerical framework explicitly coping for non-stationarity in avalanche dynamics will be developed. It will be used to reconstruct, on selected hot-spots (specific avalanche paths mostly located in Haute Maurienne and Quyras), past avalanche events that occurred mostly over the last 200 years. From this, changes in local magnitude-frequency relationships will be inferred and, combined with elements at risk and damage susceptibility relations, changes in the related risk will be evaluated. This should provide new insights of unprecedented precision regarding past changes in avalanche risk, their climatic control, and their co-evolution with social practices and forest ecosystems. For instance, we should be able to highlight different behaviors of flow dynamics at the climax of the Little Ice Age and for the warmest, most recent, decades, thus refining our knowledge on the influence of predominant control variables on snow rheology. Also, we expect better understanding of the protective effect of forest cover, and how its interaction with avalanche activity results (or not) in an equilibrium state. Hence, even if the PhD will mostly involve applied mathematics, it will be a contribution to a wider interdisciplinary initiative involving historians, climatologists and ecologists in addition to statisticians and snow and avalanche specialists.