INFLUENCE OF THE CONNECTIVITY WITH PERMAFROST ON THE DEBRIS-FLOW TRIGGERING IN HIGH-ALPINE ENVIRONMENT — IJEGE
 
 
You are here: Focus and scope Issues from 2005 to 2018 5th International Conference on Debris-Flow Hazards "Mitigation, Mechanics, Prediction and Assessment" Topic 1 - Debris-flow Occurrence and Initiation INFLUENCE OF THE CONNECTIVITY WITH PERMAFROST ON THE DEBRIS-FLOW TRIGGERING IN HIGH-ALPINE ENVIRONMENT
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INFLUENCE OF THE CONNECTIVITY WITH PERMAFROST ON THE DEBRIS-FLOW TRIGGERING IN HIGH-ALPINE ENVIRONMENT



Abstract:
The study area is the Bonnard glacier which lies in the Anniviers Valley, Valais, Switzerland. Two glacial torrents originate from a source area that is composed of 60% of creeping permafrost which supplies loose material. Heavy rainfall events trigger debris flows on the steep slopes of the lower permafrost complex. Three scarps are visible, two of them from the last event in 2008. In scar n°1 the permafrost plays a key role in triggering debris flow by loading the streambed with unstable materials and creating an impervious layer due to the presence of ice and/or frozen ground. In scar n° 2 the triggering follows shallow landslide liquefaction with no signs of permafrost, though we know that it surrounds this area. There, we assume that the water circulation, influenced by frozen layer upstream is a key factor. Scar n°3 shows only superficial erosion that contributes to gully recharge. Four processes of debris-flow triggering related to permafrost can be highlighted: cohesion loss of sediments due to thaw in the matrix, cohesion reduction due to the constant creeping, spatio-temporal changes in water circulation and constant rejuvenation of sediment on the slope. For this site, the permafrost complex is a key factor for the triggering of debris flow, although we should take into consideration all other geomechanical processes that may occur in loose sediments.

Authors:
Eric Bardou - Research Center on Alpine Environment CREALP, r. de l'Industrie 45, CH-1950 Sion
Guillaume Favre-Bulle - Research Center on Alpine Environment CREALP, r. de l'Industrie 45, CH-1950 Sion
Pascal Ornstein - Research Center on Alpine Environment CREALP, r. de l'Industrie 45, CH-1950 Sion
Jean-Daniel Rouiller - Research Center on Alpine Environment CREALP, r. de l'Industrie 45, CH-1950 Sion
Keywords
alpine debris flow, triggering, permafrost
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