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Hazard induced by debris-flow released from glacial lake outbursts : runout modeling at the Chauvet Rock Glacier, South French Alps

6 juin 2013

Mathieu, A., Malet, J.-P., Guibert, L., Buckel, C., Remaître, A.

Institut de Physique du Globe de Strasbourg, CNRS UMR 7516, Université de Strasbourg, 5 rue Descartes, F-67084 Strasbourg Cedex

The Chauvet Rock Glacier (South French Alps) has experienced events of glacial lake outbursts since 1950 of different intensity. The latest event in July 2008 triggered a 1.5 km long mobile debris-flow that reached the valley floor. It is therefore important to characterize the behaviour of possible future events, and estimate the probability of temporarily blocking the river flow. The objective of this work is to provide quantitative estimate of runout characteristics (runout distance, debris heights, kinetic energy) for different scenarios (triggered volumes, sediment rheology). The modeling exercise is carried out with the numerical code MassMov2D. The topography is provided by an airbone LiDAR survey which allows a detailed description of the surface. Rheological values are estimated on the basis of a review of sediment flows observed in similar geological contexts. Several scenarios are proposed for different source volumes and mode of failures based on a slope stability analysis of the rock glacier dam. Results allow estimating 1) the minimum volume (for a given rheology) required to reach the valley floor, and 2) to quantify the possibility of obstruction of the valley floor according to the geometry of the river fan.





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