IDENTIFICATION OF BEDROCK TOPOGRAPHY-RELATED ICE FRACTURES IN THE PLANPINCIEUX GLACIER USING HELICOPTER-BORNE GPR AND DTM ANALYSIS

In the last years, large portions of the Planpincieux Glacier became unstable and menaced to break-off toward one of the most touristic Alpine areas in Italy. Runout simulations have been conducted, but they were driven by the actual volume involved in the collapse. During the critical periods, the widening of large transversal fractures in the glacier body caused the destabilization of ice chunks that can break-off. The position of such fractures is recurrent throughout the years, with planimetric median deviations from 8 to 17 m. Combining the data of ground-penetrating radar and digital terrain models, we were able to measure the glacier thickness (20 to 60 m ± 10) and to derive the bedrock and glacier surface sections. We observed a strong spatial correspondence between the bedrock topography and the position of the major glacier fractures. Such a correspondence has been rarely demonstrated in Alpine glaciers, and it might help in the glacier-related risk assessment.