Is forest a robust indicator of rockfall dynamics within the context of environmental changes?

• Main Author: Mainieri, Robin
• Other Authors: Territoires (Territoires), AgroParisTech-VetAgro Sup - Institut national d'enseignement supérieur et de recherche en alimentation, santé animale, sciences agronomiques et de l'environnement (VAS)-Université Clermont Auvergne 2017-2020 (UCA 2017-2020 )-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Université Grenoble Alpes 2020-., Franck Bourrier, Christophe Corona
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2020
• Subjects: Statistics; Calcareous french prealps; Rockfall; Rockfall modelling; Global changes; Préalpes calcaires; Changements environnementaux; Chutes de blocs; Statistiques; Modélisation; [SHS.ENVIR]Humanities and Social Sciences/Environmental studies; permafrost
• Online Access: https://theses.hal.science/tel-02894983; https://theses.hal.science/tel-02894983v2/document; https://theses.hal.science/tel-02894983v2/file/MAINIERI_2020_archivage.pdf

Rockfalls are one of the most common geomorphological processes in the steeply sloping environments. Despite their limited volumes, rockfalls pose a significant hazard, due to their rapid evolution, high velocity and impact energy, but their unpredictable occurrence hinders detailed investigation of their dynamics and drivers under natural conditions. As the relative influence of rainfall, snowmelt, temperature, or freeze–thaw cycles have long been identified, based on medium-term monitoring methods, as the main drivers of rockfall activity, increasing rockfall hazards triggered by climate change are a major concern expressed both in scientific and non-scientific media.At high altitude sites, unequivocal relationships have been established between heightened rockfall activity, permafrost thawing and global warming. By contrast, below the permafrost limit, in the absence of longer-term assessments of rockfall triggers and possible changes thereof, our knowledge of rockfall dynamics remains still lacunary as a result of the persisting scarcity of exhaustive and precise rockfall databases.Over the last two decades, dendrogeomorphology – based on the analysis of damage inflicted to trees after rockfall impacts – has been used to overcome certain limitations inherent to historical archives and reconstructions of rockfall activity have been developed. Paradoxically, tree-ring reconstructions have only rarely been compared with climatic data to precisely constrain the potential meteorological triggers of process activity or to detect potential influences of global warming mostly due to the absence of clear recommendations to derive reconstructions that optimally capture the climatic signal in rockfall-prone environments.In this context, this PhD thesis first aims at proposing clear methodological guidelines to optimize sampling strategies of trees so as to precisely quantify uncertainties in dendrogeomorphic reconstructions back in time. Our results clearly evidence that the high-resolution mapping of stems on the ...