The first snows of winter have finally arrived. Everyone is excited to be getting some turns. I was wondering how to present a distillation of the main points concerning avalanches when I was alerted to this film made by the Utah Avalanche Center and the Colorado Avalanche Information Center (amongst others) that basically covers “The Rules”. It is worth watching.
The second you cross outside the piste markings you are in the mountains with all associated dangers and risks. These are different from open and marked ski runs, the principal danger for winter sports enthusiasts are avalanches. People have been killed just meters from open ski runs. Are you properly equipped? Do you know the area? Can you rescue one of your companions? Do you know how to evaluate the terrain and snow conditions? Let’s be clear, there is plenty of safe terrain off piste but there are also hidden dangers as Michael Schumacher accident reminds us.
http://pistehors.com/news/ski/comments/tignes-ski-piste-director-talks-safety/
There tends to be a lot of fatalism surrounding avalanche accidents but 90% of avalanches involving skiers are slabs triggered by the skier or someone in his party. To a large extent you are in control of your destiny. A slab is an area of cohesive snow that detaches from the surrounding slope and flows down the mountain before stopping. The bad news is you can ski in perfect, light powder and trigger a slab, they are not visible to the eye and even a small slab can bury a skier under meters of snow depending on the slope configuration. The good news is, we understand a great deal about snow slabs, where they are likely to occur and how to avoid them.
http://pistehors.com/backcountry/wiki/Avalanches/Slab-Avalanches
http://pistehors.com/persistent-slab-avalanches-23707683.htm
http://pistehors.com/news/ski/comments/slab-avalanche-mechanics/
85% of off piste avalanche accidents occur after fresh snowfall. Even 20cm of new snow can be dangerous. Wait for the snowpack to stabilize before heading onto avalanche prone slopes. Wind is like an accelerator. 65% of accidents occur after snow transport due to wind. A few cms of snow moved by wind can quickly lay traps on the slopes. Fresh snow and wind can create temporary weak layers in the snow pack. Good weather, sun and clear skies typical of winter anticyclonic conditions, encourage the development of persistent weak layers in the snowpack. Covered with new snow these are like detonators waiting for a backcountry traveller to cross them.
Dry slab avalanches can be triggered on any slope above 30° steepness. That’s is the kind of slope found on a typical black or hard red run. We are not talking the average slope angle from top to bottom but any measurable section of slope. That could be a roll-over on a generally mild slope. Now obviously a small section of 30° surrounded by flatter terrain will not run very far but could still be tons of snow on top of you. In general an avalanche will run to an angle of around 20° from the trigger point. Look around, how steep are the slopes above? Am I in the runout zone? In the Winter of 2015 a skier in a guided group was killed by a small slide as they passed under a slope touring to the Galibier mountain pass. The majority of avalanche accidents occur on shaded slopes. Depending on the season this is a large sector from West through to North to North-East. These “cold” slopes slow down any stabilization of the snowpack and frequently develop weak layers. This can include small shaded sections on generally sun exposed East and West sector slopes. Very heavily tracked slopes can help stabilization as the skis break up weak layers. We’re talking popular off piste routes.
http://pistehors.com/route-planning-in-avalanche-terrain-23169015.htm
Trees, cliff bands, streams, lakes, hollows and holes, crevasses, couloirs, even rapid change in slope angle. Even small slabs can have fatal consequences if the snow is channeled into one of these traps. Rescue services frequently have to bring in heavy digging equipment for summer avalanches on Mont Blanc where climbers have been swept into a crevasse. An avalanche in 2015 on the Charmant Som near Grenoble took the life of a skier. The slab was only a few cm of wind blown snow but was channelled by a couloir before banking up in a terrain trap. The skier was buried under 150cm of snow.
http://pistehors.com/backcountry/wiki/Avalanches/Reading-Terrain-I
http://pistehors.com/backcountry/wiki/Avalanches/Reading-Terrain-II
http://pistehors.com/backcountry/wiki/Avalanches/Reading-Terrain-III
Never follow tracks if you don’t know where they lead. Every season skiers die or have to be rescued in la Grave following tracks down the steep couloirs, many of which require ropes to descend safely. Consult guidebooks or websites and take detailed topographical maps of the area you will ski, and know how to read them. Small cliffs, which can present difficulties for skiers, are frequently unmarked. Check out the avalanche bulletin or check the resort warning flags. On risk 3 and 4 days you should keep off avalanche prone slopes: slopes over 30 degrees, big, open faces, couloirs with avalanche funnels at the top, slopes with terrain traps, aspects mentioned in the bulletin. Remember both level 3 and 4 are in the upper half of avalanche dangers facing skiers.
Never go alone on slopes where there are few skiers. The smallest incident can be extremely serious. Backcountry travellers have died from a fall or by even being partially buried in a slide. Incidents that would have been minor if they’d been with a friend or there were eye witnesses. On any slope above 30° ski and ideally climb one at a time. For ski touring and snowshoeing this can mean taking a different, safer, route to climb. Ski between islands of safety but be aware that avalanches can be much bigger than expected. Last January (2015) an avalanche on the Foglietta took out the whole north facing bowl overwhelming the spot where skiers were waiting. It was typically of incidents last season along the mountains bordering with Italy where a widespread, homogeneous weak layer had developed early in the winter (read the bulletin details). Consider walkie-talkies or have good protocols for communication where skiers are widely spaced. Keep your tracks close, this limits the chance of hitting a weak layer assuming the first track was safe (spatial variability). However avoid skiing directly on previous tracks as you increase the risk of cutting down to a more deeply buried weak layer. Ski light and try not to fall. If you are not sure, don’t ski the slope. Turn back or find a safer alternative.
Our brain sometimes plays tricks on us or takes short cuts when evaluating conflicting information. Groups can give a false sense of security and a group leader may be chosen for reasons other than their ability to judge avalanche terrain. Listen to all group members opinions. A group is only as strong as its weakest member, take this into account when making choices. Don’t get lulled into a sense of security by bluebird days, sunny conditions following fresh snow are frequently the most dangerous due to weak layers and new slabs. The majority of avalanche victims are male, middle aged and experienced. To some extent this represents who is actually skiing off piste but years of skiing without incident can make people complacent about the risks.
http://pistehors.com/backcountry/wiki/Avalanches/Heuristic-Traps
http://pistehors.com/chris-davenports-avalanche-avoidance-tips-23173579.htm
Probe, shovel and avalanche beacon are a minimum. The French Mountaineering Federation recommends that everyone moves to 3 antenna beacons for their ease of use. They will be mandating this for competitions. Even if skiing alone take a beacon, it can help the rescue services to locate you and enables you to help other skiers if you witness an avalanche. Statistics show that a beacon only gives you a 50% chance if you are buried by an avalanche. Airbags increase survivability if used intelligently but high risk days on open slopes, terrain traps, thin snowpacks on rocky slopes, and lack of training can all render the advantages null and void. Once you are caught in a slide there is a certain amount of chance so the best tool you have is your brain.
Know how to react in case of an avalanche both if you are caught (cover airways, create an air pocket if possible, jettison ski poles and skis) and if you are searching: where did you last see the victim, visible surface clues, make sure the rescuers are not putting themselves at risk, alert outside help, organize the rescue with beacons, probing and shovelling. Do you know the rescue services phone number for your area? Can you give them a grid reference or location?
http://pistehors.com/backcountry/wiki/Avalanches/Localization-With-An-Avalanche-Transceiver
http://kbyg.org/
http://www.anena.org/
http://www.henrysavalanchetalk.com/