there seem to have been a lot of pistes hit by slides this year and it must worry resorts as it is not easy to account for these. You can set off a charge equivalent to 500 skiers doing jump turns on the slope, nothing happens, a few hours later the whole slope goes. Normally they are slow moving, about the speed of a skier, so you should be able to get out the way if you are on piste but they can be dangerous if you are in a terrain trap, such as a gulley where you can be overwhelmed or crossing an avalanche couloir.
Avalanches: a sword of Damocles hangs over the stations
It’s an full depth avalanche that almost caught two skiers on the Crosets on Sunday. This type of slide is unpredictable
Monday on the trail of Mossettes skiers were enjoying themselves skiing down the snowy run. Early Sunday afternoon, however, the tension was at its height when an avalanche 100 feet long broke out and swept part of the track. Witnesses claimed that two people had been caught by the slide. Fortunately, this was not the case.
This event raises questions: the avalanche could it be avoided? Officials from the ski lifts had they noticed the cracks that had formed downstream of the track, as observed by a witness just before the snow slid? “This type of slide is called a full depth avalanche, it is unpredictable,” says Francis Perrin, head of Slope Safety at Tele-Champery-Les Crosets. And for good reason: the white gold of the early season was deposited on ground that was not frozen. The snow rests on an unstable base which is struggling to hold the weight of the snow.
Off piste, all can give any time as soon as temperatures rise, as is the case here. “We have taken the necessary precautions” Would it not have been simpler to set of explosives? “It’s useless. You can use a load of 1000 kg or 10, it will only make a hole! “
A view shared by John Paul Jotterand, head of the ski lifts of Les Diablerets. “This type of slab can not be removed using explosives.” The Waldensian station also has problems with depth avalanches. For three weeks, the connecting track between Isenau and Glacier 3000 is closed. “A ‘whale’s mouth’ (glide crack) has formed above the route. As a precaution, we closed the track. But it is difficult to predict when the slide will happen.”
In Verbier, an full depth avalanche was also triggered last weekend. “It happened around 17h15 over the road from Savoleyres said Eric Balet, director of Téléverbier. Prior to slide, we decided to close the run to avoid any incidents. How did the Valais resort forsee such an avalanche? “It’s a matter of luck, Eric Balet answers. This is a virtually unmanageable. All we can do is constantly patrol whenever there is a risk. “
In terms of risk, wet snow avalanches should not cause panic among skiers and snowboarders, as stated in Luke Défago, director of the Swiss Ski in Champery. “There is no big risk on the slopes of the region. For once the weather is nice during the holiday weeks it would be a pity if skiers do not enjoy the sun! “
The avalanche Sunday was it unpredictable?
Interview with Philippe Aigroz, Observer for the Swiss Institute for the Study of Snow and Avalanche.
When in doubt, should the head of security at Crosets have shut this sector?
- This is for an investigation to determine, not me. It is always easier to say that there was a risk once there has been an avalanche. This type of slide is difficult to detect and control. In the case of a a slab avalanche, we know it will take place immediately after the snowfall. It can be triggered by mining hazard areas. Since December, the snowpack has had time to settle and transform. One can hardly guess when it will slide.
The danger is it especially high this season?
- Many factors affect the snowpack. The fact that the earth has not had time to freeze before the first falls is one. In December, we experienced “hot snow”. Five or ten inches above the ground, we are left with a layer 0.2 or 0.5 degree. All this means that the risk is high. This year, we had an avalanche at 1100 meters in the Jura, which remains a rare phenomenon. We are faced with a very unusual snow and it was difficult to assess its strength.
So what will this end of season, in terms of avalanche risk?
- With Spring Break, we are in a warm period, both in terms of climate danger. It’s hot, which increases the risk, and sunny: people may be more likely to hike these days. After? Everything will depend on weather conditions. Will the warming will continue or will it start to freeze at night? If it snows, what is the quality of precipitation? If it rains or the foehn rises, the risk will remain high. I am no prophet, but statistics show that these ground avalanches will pose more problems in the future.