Snow avalanche hazard assessment in the French Alps using a combination of dendrogeomorphic and statistical approaches

Abstract : Snow avalanches are a significant natural hazard that impact roads, structures and threaten human lives in mountainous terrain. The extent of avalanches is usually evaluated using topographic or statistic models. These models are well capable to simulate contemporary events, but uncertainties increase as soon as longer return periods are investigated. Thus, there is a real need for validation of modelling procedures to corroborate model predictions. In the present work, dendrogeomorphology has been used as a validation tool. This approach is based on the fact that trees affected by mass movements record the evidence of geomorphic disturbance in their growth-ring series and thereby provide a precise geochronological tool for the reconstruction of past mass movement activity. This PhD thesis presents a new tree-ring-based semi-quantitative approach for the identification of avalanche events based on the analytical skills of the dendrogeomorphic expert and proposes an evaluation of the completeness of tree-ring records. Furthermore, this work proposes the first cross-validation of high return period avalanches derived from a locally calibrated statistical-dynamical model and the long-term, higher-return period information gathered from tree-ring records. Comparison of relations between runout distances and return periods between both approaches shows very good agreement for events with return periods of < 300 yr. Finally, a statistical analysis of avalanche-climate relations suggests that tree rings preferentially record events that occurred during cold winter storms with heavy precipitation.
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Romain Schläppy. Snow avalanche hazard assessment in the French Alps using a combination of dendrogeomorphic and statistical approaches. Geography. Université Panthéon-Sorbonne - Paris I; Université de Berne, 2014. English. ⟨NNT : 2014PA010679⟩. ⟨tel-02188098⟩

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