understanding avalanches II

Facewest are specialists in backcountry equipmentThe golden rule of back country or off piste skiing is to AVOID avalanches. Everyone should be properly equipped and trained to deal with an avalanche but nobody should ever have to! 

This article from Facewest, specialists in backcountry equipment, helps to explain how you can reduce the risks.  

This article is written about skiing but applies exactly the same to snowboarding.

1.History

You should be aware of the local conditions before you go out. When did it last snow? Are there any slopes that always avalanche? Has it been warm or cold? How many snowfalls have there been this season? How windy has it been? Have there been many avalanches this season? All these questions give you an idea of the risk you are facing. There is no substitute for local experience and knowledge. You are most at risk just after a snowfall and the more snow that fell the greater the risk.

New snow added in 3 daysObserved Avalanches
Up to 10cmrare avalanches, mostly loose snow
10 – 30 cmvery occasional slabs, frequent sloughs
30 – 50 cmfrequent slabs on slopes 35 degrees
50 – 80 cmwidespread slabs on slopes down to 25 degrees

2. Slope selection

You have found the answers to the above and have decided it is an acceptable risk to ski off piste. You have seen a slope that you really want to go down, there are some important questions to be answered about this slope.

How steep is it? 
Below 25 degrees is not steep enough to slide, above 50 degrees is too steep to hold a lot of snow, anywhere between is prime avalanche territory

Is the slope concave or convex? 
Convex slopes do not support the weight of the snow high up very well and are more prone to avalanche

What is the slopes aspect? 
North facing slopes are less affected by the sun and colder just after it has snowed, south facing slopes consolidate more quickly and are safer a few days after the snowfall. This is especially true in the springtime where south slopes consolidate quickly and north facing ones can remain dangerous for days or weeks after a snow fall.

Is the snow wind affected? 
If the wind has been from behind the slope it will have deposited a lot of snow on the slope and given it a pillowed effect. There is now a great weight of snow to be supported and the risk is higher. If the wind was strong as well it may have formed a slab, where the snow has been blasted together in one huge lump. In this case the risk is high and if there is an avalanche it is sure to be a big one. If the wind was up the slope it will be scoured, and most of the loose snow removed , this will be safer but the conditions not as good. A cross slope wind will give both conditions at different places on the slope. The ideal is for the snow to fall in still conditions but that happens only when there is a blue moon!

What time is it? 
How much sun has your slope received today. A slope can be safe at 10.30, dodgy by midday and downright dangerous by 1.30. The avalanche risk changes all the time, just because there are tracks does not mean it is safe!

What is the ‘run out’ like? 
If your slope fans out into a wide gentle area, an avalanche will slow down and spread out reducing your chances of being buried, if it runs into a gully or depression you may be buried under many metres of snow and digging you out could take hours

3. General tips

If your assessment has revealed that the slope is too risky then walk away. It is tempting just to say ‘fuck it, I’m going down’ especially if the snow conditions are good, and you may escape incident this time. But that attitude will eventually get you killed. You can ski many more slopes in ten years safely, than skiing all the slopes all the time until you get killed.

Hopefully you have answered all these questions and decided it is ok to ski down. That, after all, is why you are there. These hints will further increase your security.

  • At the start of the day check all transceivers are on, switched to transmit and have good batteries. It is worth actually testing all the transceivers. Never take it off during the day.
  • Never ski off piste alone, big groups are also dangerous because of the weight and difficulty of controlling everyone. 4 is the ideal size of party.
  • Loosen your backpack and take your hands out of the pole straps. These can easily be dumped if the worst happens.
  • Only one person should move at a time, the others should be watching him in case he is avalanched
  • Try to move from one safe spot to another, i.e. the top of the slope to below the big rocks halfway down and on the left side. If there is an avalanche that someone else starts you don’t want it to get you as well
  • Ski down the edges of bowls and not down the middle
  • Ski down ridges and spurs rather than bowls and gullies
  • Do not bunch up. This places extra stress on the snow pack and weakens it
  • Do not ski directly above someone else, you are putting them in danger
  • Do not traverse slopes. If this is unavoidable traverse as high up as possible. Never traverse above other skiers.
  • Watch and listen for cracks and movement in the snowpack, you may get a warning to be very careful!
  • Avoid skiing under cornices. They are evidence of wind loading and may fall off and cause an avalanche.

[Article courtesy of Facewest - to buy backcountry equipment, check out our online store]

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