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Avalanche Safety

Disclaimer
This is not a replacement for an avalanche course, I am not a mountain guide and have no qualifications of any sort in back country or off piste safety. If you are going off piste you need to learn as much as possible the aim of this post is to encourage you to go and learn more not to take anything posted here as gospel.

Definitions: (as I see them and used here)

Off Piste: Off the marked and prepared ski areas in a resort. This includes marked "freeride" runs which some resorts now feature.

Out of Bounds: Riding away from a resort, ducking under the yellow and black ropes at a resort, or riding areas of a resort that are not indicated on any piste map.

Freeriding: Riding off Piste or Out of Bounds where the emphasis is on riding down. The lifts are used as much as possible and any uphill walking or skiing is kept to a minimum.

Touring: Riding off piste or out of bounds where nearly as much emphasis is based on going uphill as going down. Ski/Snowboard touring is as much about the journey as it is about the actual skiing.

Avalanches:
Avalanches are a major concern if you ride off piste. Even riding beside the piste in ski areas can have fatal consequences if you do not take conditions into account. In winter 2007/2008 there were two incidents where a child was killed riding just beside a piste in Davos, the Avalanche that killed her ran across the piste and endangered people who were riding on piste. A skier on the piste was killed in a similar incident in Wallis when another avalanche crossed the piste.

An avalanche occurs when a layer of snow looses its grip on the layer or ground underneath. In fresh snowfalls there can be powder avalanches when freshly fallen powder which has not yet bonded to the underlying snow layer slides down the mountain. As time progresses the loose powder compacts and becomes a heavier slab. Slab avalanches occur when a "snowboard" or slab releases and slides down the mountain. Slab avalanches are probably the more dangerous but all avalanche types can be dangerous.

The avalanche risk increases after any new snowfall, after wind has created new snowdrift formations, or when the suns radiation causes the snowpack to warm up to a point where it becomes unstable. Even a stable snowpack which has had a long time to settle can have weak layers in it and may slide when an additional load is placed on it.

Avalanche Risk Levels in Europe

1: Gering (Low)
Natural avalanches very unlikely. Human triggered avalanches unlikely. Generally stable snow. Isolated areas of instability.
2: Mässig (Moderate) Natural avalanches unlikely. Human triggered avalanches possible. Unstable slabs possible on steep terrain. Use caution on steeper terrain with certain aspects (defined in avalanche bulletin).
3: Erheblich (Considerable) Natural avalanches possible. Human triggered avalanches probable. Unstable slabs probable on steep terrain. Be increasingly cautious on steeper terrain.
4: Gross (High) Natural and human triggered avalanches are likely. Unstable slabs likely on a variety of aspects and slope angles. Travel in avalanche terrain is not recommended.
5: Sehr Gross (Very High) Widespread natural or human triggered avalanches are certain.

Moderately steep slopes: slopes with an inclination of less then 30 degrees.
Steep slopes: Slopes steeper then 30 degrees.

The Avalanche Bulletin
The avalanche bulletin can be got each day at around 5pm from www.slf.ch There is a written avalanche report and a hazard map showing the risk levels through out Switzerland.

The regional avalanche bulletin is only available in German and is issued at about 8am on the day it is for.

When planning your day off piste you can use the Hazard map and national bulletin to choose your routes. The routes should be assessed again in the morning when the regional bulletin is released. Most resorts have "Freeride Checkpoints" where the post the regional avalanche bulletin.


What do I need to go off piste?
Generally if you are riding in avalanche terrain you need as a minimum the following equipment.
  • Avalanche Transceiver
  • Shovel
  • Avalanche Probe
  • First aid kit
  • Means to summon help
  • Suitable Map
Having the equipment is only part of the equation. It all needs to be operational and every member of the group needs to know how to use it. If you ride alone the safety equipment is close to useless!

There is an 80%+ survival rate for people who are buried in avalanches that can be found in under 15 minutes. 90%+ if found in under 10 minutes. The chances of survival drop exponentially after 15 minutes. If someone is buried rescue by the group is the only realistic chance of survival. This is why it is essential that you never travel in avalanche terrain alone, and that you know exactly what to do in a real life situation.

Minimising Avalanche Risk:
The 3x3 method and reduction method are two tools which have been developed to reduce the risk for those travelling in avalanche terrain. The 3x3 or filter method involves you creating a filter to avoid the chances of you travelling in an area where the risk is too high.

The first level of the filter takes in regional information, the second level takes in local information and the last part takes in Zone information. Some more information on the 3x3 method can be found here.

When you have decided that it is safe to go with the filter method then the reduction method is aimed to further reduce the remaining risk.

The reduction method is based on the following formula.

Acceptable remaining risk = danger potential/(product of safety measures).

The outcome of this formula should be <1.

Some further information and explanation of the danger potential and safety measures of the reduction method can be found here.

As the avalanche danger level goes up 1 point on the scale, the danger level doubles!!! If Level 1 has a danger level of 2, Level 2 has a danger level of 4, Level 3 has a danger level of 8 and Level 4 has a danger level of 16!!!!!

When using these rules you should always err on the side of caution. In avalanche danger 3 you need to consider the whole slope not just the area you are riding.

Route Planning
If you are going off piste, a piste map is not any use to you. You need a proper survey map with a scale of 1:25,000. In Switzerland these can be got from any good bookshop our outdoor store. For season 2008/2009 a new map has become available for some areas. This freeride map shows some of the better know freeride areas in the featured resorts. They grade the difficulty level of the terrain and give some suggested routes. The maps are not a substitute for knowledge, you need to be able to spot safe routes for the avalanche risk level when you are in the area. To do this you need to know how to measure the slope angle off the map. This is only possible with the 1:25,000 scale maps. There is a card available from any good mountain sports shop which allows you to measure the slope angle from the 1:25,000 maps. If you are using this card remember to add one degree to the reading you measure.

There are also 1:50,000 ski tour maps available. These maps are good for a general overview of a route, but may not be of high enough resolution to navigate effectively. The slope measurement card will not work with these maps but slopes of over 30 degrees are highlighted in red and should be avoided at critical avalanche risk levels.

When planning your route always make sure to measure the steepest slope you expect to travel on. At avalanche risk of 3 and above you must also measure the steepest area in the whole region you are in. Remember an avalanche which releases above you can travel down the mountain to you, or remotely trigger a slide where you are.

Slope Exposure
The avalanche bulletin will mention slopes exposures that are particularly dangerous on a given day. In general in mid winter the northern half of the compass West through North to East is the most dangerous. This is because these slopes get less sun with the sun low in the sky and reduces the settling possible in the snowpack. In spring this reverses and the southern half of the compass is more dangerous. Rapid heating of the snowpack during the day cause weaknesses in the snowpack and wet snow avalanches occer. In spring you need to be off the mountain before the snow has time to warm up, riding off piste after midday carries extreme risk.

But there are tracks there!
Just because you see tracks go somewhere ahead of you does not mean it is safe. These tracks may ride straight off a cliff, or the people before you may have been lucky enough not to ride over a trigger point in the snow. If a slope is tracked enough for it to be totally avalanche safe then it is probably not fun to ride anymore!

But I'm in the trees!
For trees to provide safety from an avalanche they need to be so close together that you can't ride in them.

Is Switzerland more dangerous then other countries for Freeriding/Touring?
Yes, Switzerland is more dangerous then many areas in the US and the Pyrenees. Switzerland is further inland then many resorts in other areas in Europe and the states. Therefore there is less of a salt content in the snow meaning a drier snowfall. This snow does not adhere to itself as well as the snow that falls in maritime areas meaning less stability in the snowpack. We also get less snowfall annually here then in many other areas. This leads to a thinner snowpack which has a higher temperature difference between the top and bottom of the snowpack and less pressure compressing the lower layers in the snow. These factors can allow for more weak layers in the snow where a slide can trigger. Just because you see guys in videos riding super steep slopes it does not mean it is safe for you to do it here in Switzerland.

Avalanche Safety Courses
Many mountain guide companies throughout Switzerland run avalanche safety courses during the winter months. These courses offer a good way of getting some basic knowledge in a supervised setting. Anyone planning on going off piste (even in ski areas) should take one of these courses. We run Avalanche safety courses at the start of each winter with qualified local mountain guides for Swiss Alpine Adventure members.

Guided Freeride/Touring
If you are just starting to get into off piste skiing or snowboarding hiring a guide for a day is a good idea. The guides will plan as safe a route as possible for you and do their best to try to keep you out of trouble.


Further Reading
The Powder Guide, Tobias Kurzeder and Holger Feist
3x3, Werner Munter

White Risk interactive avalanche DVD

SLF
record of fatal avalanche accidents.
SLF publications in English
Recommended publicatons from SLF

Avalanche Safety Statitics (German only)
New Trends of recreational avalanche accidents in Switzerland
, Paper.


Once again, I am not a guide or am not qualified in any way to give avalanche training. I have undergone a couple of avalanche safety courses and attended some sessions on tour planning. I have also read any pieces of information in English or German that I could get on European avalanche risk. Do not take my word for the truth. Perform your own research, do some courses and learn how to be safe in the mountains.