Safety concept for hazards caused by ice avalanches from the Whymper hanging glacier in the Mont Blanc Massif

The Whymper glacier is a hanging glacier located on the south face of the Grandes Jorasses (Mont Blanc Massif, Italy). Combined snow and ice avalanches triggered by ice masses breaking off from the hanging glacier endanger the village of Planpincieux and its surroundings in the Val Ferret. In 1997, the SLF and the VAW developed the first safety concept for the village for several scenarios based on the monitoring of the glacier and an assessment of the local avalanche hazard. At the end of June 1998 almost the entire Whymper glacier (around 150,000 m3) sheared off and the ice avalanche stopped only 500 m above the valley road. The Whymper glacier has grown back and now has a similar surface topography as in 1998. The SLF and VAW improved the 1997 safety concept by considering several scenarios of falling ice volumes. The different ice avalanche scenarios were simulated using the 2-dimensional calculation model RAMMS. The necessary safety measures are defined in relation to the local avalanche danger level and the potential volume of an icefall. The hanging glacier is continuously monitored with a system consisting of a total station, GPS-stations, seismic sensors and visual observations. The improved safety concept has been operational since 2009. However, a dangerous icefall has not occurred yet.

Research Highlights
► A safety concept for hazards caused by ice avalanches was developed.
► We modelled ice avalanches successfully with RAMMS.
► Safety measures depend on the avalanche danger and the volume of a potential ice fall.
► The hanging glacier was continuously monitored with an improved observation system.
► An icefall could be accurately forecasted.