All photography copyright David Pickford / www.davidpickford.com.
1. Local knowledge
The very first thing to do before heading out off piste is to check all available sources of local knowledge. You need to establish where it is safe to ski, and where should be avoided.
Giles Cornah charges a 35-degree powder slope in the Ecrins. To ski avalanche-prone terrain like this safely, local knowledge and a detailed awareness of the stability of the snowpack are crucial.
Avalanche prone areas use an internationally recognised scale for assessing the avalanche risk in a given area. The scale ranges from 1 (pretty safe) to 5 (very high risk of sliding in this area).
Every day in any major ski area, the local staff helpfully post an avalanche warning for the area. This can cover a wide region or it can be very localised. The level of technical detail varies, but pretty much all warnings use the standard 5 point scale.
The rule is very simple. If the scale says 3, think really hard about whether you want to be in off-piste. If it says 4 or 5 – forget it and stay at home or on the piste.
Local experts will also know which slopes are likely to slide (and when!) and will also have a detailed knowledge of the history of the snowpack which can give vital clues to the potential for dangerous buried layers of poorly bonded snow. Ask around before you go out!
Avalanches occur when the force of gravity on the snowpack and the pressure you add overcomes the friction that is holding the snow to a slope. Gravity is constant, so the two variables (apart from your presence) are the amount of snow and the amount of friction. Poor friction is the reason why slopes often slide in layers where a new fall of snow binds weakly to the older snow below.
Three types of weather tend to increase the amount of snow or reduce friction and thus increase the risk of a slide:
Any one of these factors increases the risk of a slide. During winter, avalanches usually come down with 24 to 48 hours of fresh snow when the slopes are heavily loaded and the new snow has not had time to bond to the old. European research suggests that some 80-90% of alpine avalanches happen within 24 hours of fresh snow. In the spring, warm weather can also unsettle slopes. Add it together and you’ll see that the most dangerous conditions of all are a warm sunny day with blue skies, immediately after a heavy snowfall with high wind – or in other words “a perfect powder day”. A lot of bad accidents happen on days like that. The rule is simple. If you observe:
3. Spotting dangerous slopes
Some slopes are inherently more dangerous than others. In questionable conditions, the trick is to stay away from the dangerous ones. To do this, you need to recognise the following potential danger signs:
Skiers assess a big-mountain line high above the Col de Balme, Argentiere. Although there has been no fresh snowfall for several days, wind-loading has created a moderate avalanche risk. The skiers therefore chose the safest line - the ridge feature marked by the arrow, on which the snow will be less deep and less prone to sliding.
Avalanches pretty much always start on slopes with an angle of between 30 and 45 degrees . Any steeper and the slow falls off before it can build up to dangerous levels. Any shallower and there’s not enough force for the slope to “go”. You can use an inclinometer to measure slope angle (it’s pretty difficult to judge without practice). Alternatively, the box below shows a simple test for measuring whether the slope is between these limits (try it out on your favourite black run - it can be quite humbling to realise that something which looks vertical doesn't even reach 30 degrees!). Be aware however that it’s no good wandering merrily across a 25 degree slope if the slope above you is 40 degrees and loaded with snow! Another trap to watch out for is convex slopes where the pressure will tend to fold the snow away from the slope and can lead to potential fracture lines.
Avalanches tend to come down when slopes get unstable – usually when they’ve been warmed by the sun. For this reason, South facing slopes (which get more sun ) are more prone to slide than North facing slopes. Slopes are more dangerous in the afternoon when the sun has been out than in the early morning. A South facing slope late in the afternoon after a fall of fresh snow is a bad place to be!
Ben O'Connor-Croft making the most of chopped powder on steep ground high on Cosmiques Couloir, one of the classic ski-mountaineering descents of the Chamonix Valley. Even though the snow may not be quite as good, it's far safer than it would have been four days earlier! A sunny, south west facing slope such as this can be extremely dangerous in fresh powder, and many skiers have perished in avalanches on this descent.
Obvious danger signs: slope breaking into slabs beneath your feet, clear evidence of a loose crust, a heavily laden cornice or sun balls rolling down the slope are bad signs. Time to leave!
4. Testing slopes
Knowing the conditions which might make a slope dangerous is one thing. Testing the slope to see how dangerous it actually is can tell you a whole lot more. Off-piste experts will tell you that you should test the snow you’re in from time to time. Before skiing down or walking up a huge exposed face, test a smaller safer slope with the same aspect and steepness to see how stable the snowpack really is.
There are lots and lots of different tests. We’ll break our normal rule by describing not one but two techniques – one very quick, one a bit more time and labour intensive.
First the quick one:
Time: 5-30 seconds
How to do it:
Find a small, steep slope where the consequences of a slide are small, such as a the side of a road, by a tree stump, at the top of a small ridge, or on a small steep area on the slope. Then simply jump on the slope to see how it responds. You can find test slopes nearly anywhere if you are always on the lookout for them. Remember that even on small slopes, it’s possible to get buried. Always have the rest of your group watch from a safe spot nearby. Advantages: quick, safe and easy to interpret results. Disadvantage: Not a good test of deep weak-layers, especially ones overlain by hard slabs.
Now the more involved test: a bit time consuming, but probably the most accurate way of assessing the danger level of a suspect slope.
Time: 5-10 minutes
How to do it:
The Rutschblock test (shear block) is the standard snow pit test of choice for avalanche professionals who dig a lot of snow pits. First, on a slope of at least 30°, isolate a block of snow about a ski length across, and a ski pole length up the slope (2 meters wide by 1.5 meters long). Do this by first cutting the face of the block using your shovel, then cut out the back and sides of the block using a ski tail (photo). The process can be speeded up if you carry a snow saw, but few people other than avalanche professionals routinely go around with one of these.
Next, step onto the block with your skis or snowboard and jump progressively harder until the block fails. Most people rank the test on a scale of one through seven. The higher the number, the more stable conditions. Ideally, you’re looking for a score of 5 or more.
Advantages: duplicates what happens with a skier on the slope, easy to interpret, quantifiable. Disadvantage: takes more time and effort.
5. Safe route finding
If you have gone out for the day and are a bit worried about the conditions, there are still a number of things you can do to minimise the risk. The basic rule in dangerous or potentially dangerous conditions is to avoid steep slopes. Don’t enter them and don’t cross below them.
Sticking to safe ground on a fresh powder day in the Ecrin: note how the skier is taking a line down the wide ridge in the foreground, which is a much safer bet than the very exposed and threatened open slopes in the background (which have nonetheless been skied).
This means planning your route to stay on safe areas and away from potentially dangerous steep slopes. As a simple rule of thumb, safe havens include:
Matt Helliker enjoying a tree run in perfect powder off the base of the Toule Glacier, Italy. Tree skiing provides not only the safest but also the best skiing on deep powder days, particularly if the visibility is bad.
Dangerous areas, also known as “terrain traps”, which should be specifically avoided include:
6. The Golden Rule – one at a time
If you are out in conditions which you have reason to believe could be dangerous (avalanche risk of 3 or more, bad weather, suspect slope, iffy block test) the golden rule is never to put more than one person in danger at any one time. Let’s say an off-piste ski party of seven gets caught by an avalanche. It’s a lot better to have six people searching for one victim than one person searching for six!
In practice this means:
1) Spreading out to cross dangerous slopes.
If there is a suspect slope to cross, the correct technique is to put plenty of distance between each member of the group and cross one at a time, stopping only when you get to the next safe haven. That way, if the slope does go only one person is caught and the others can spend their time watching closely to see where they end up before coming to the rescue. The gap left should be wide enough that only one person will get caught if the slope slides. Vital point! Don’t forget to make sure that the penultimate person waits to watch the last person safely across the slope!
2) Waiting only at safe havens
It follows from the golden rule that you should never stop and wait except at a safe haven. Carry on to a safe spot away from any potential avalanche path – be this on a ridge, behind a large rock, within the shelter of large trees, or simply on a flat slope away from potential avalanche danger. Stopping half way down a steep slope is never a good idea!
3) Not bunching up at lunch stops
A particular problem – which you see surprisingly often is big groups stopping to have lunch in far from safe places. Eating sandwiches does not convey immunity from avalanches! When your group does stop for any period of time for any reason, make sure the spot is 100% safe. If there is no safe spot, you shouldn’t be stopping!
All in all, the rule is largely common sense provided you travel with a constant awareness of the potential risks.
If the worst comes to the worst and one or more of your party are buried by an avalanche one thing and one thing only matters: speed. Numerous studies have shown that survival rates are directly influenced by the speed of rescue. The sobering fact is that only 30% of victims found after more than 35 minutes are recovered alive. Conversely, those rescued within the first 15 minutes have a better than 90% chance of making it. As the diagram shows, the only real chance of finding a buried victim in time is if they are wearing a transceiver.
Your mission therefore is to find and recover the victim as fast as you possibly can and certainly within the critical first 15 minutes. This means you must find and rescue them yourselves rather than going for help. Even within pisted areas, rescue professionals may not have enough time to help some victims. In the backcountry there is very little chance outside help can arrive in time to do anything but recover the body of a dead skier.
If one of your party is caught by an avalanche, the rescue sequence is as follows:
Once the victim has been found, correct first aid treatment is essential. Suffocation is the big killer but remember that 10% of fatalities occur through shock and hypothermia after a successful rescue. The actions to take are covered in our section on Essential First Aid Skills.
8. What to do if you get caught
Advice is limited on what you can do if you are caught in a slide. The advice consists of a summary of actions that have worked for survivors. The problem is that plenty of other equally skilled individuals have tried the same things and still became fatal accident statistics. There is an element of luck involved.
The advice boils down to four key actions.
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