Avalanche Risk Mitigation

The Swiss Institute for Snow & Avalanche Research (SLF) recorded 27 deaths from Avalanches in the winter season 2021/22 up to the end of March, double the number for the previous year and the moving average over the last 20 years. All the victims were winter sports enthusiasts on unsecured terrain – 11 back country and 16 off-piste – and a quarter were in the Verbier area.

Why do skiers and snowboarders get killed by avalanches, I have often been asked. Can’t they just ski out of the path of the snow slide?

Simply put, it is almost impossible to out-run an avalanche. A skier normally travels around 30km/hr, whilst an avalanche can exceed 100km/hr, faster than all but the fastest skier can travel in perfect conditions. Additionally a skier may not be aware that an avalanche has formed until it is upon them, as they can begin with little warning and an almost imperceptible change in the condition of the snow. Then, very rapidly, the force of the product of the mass and acceleration of the slab of snow is capable of knocking over anything in its way.

Just like a flood of water, it is possible to “float” on an avalanche by wearing and deploying an avalanche airbag. Without one, however, you will almost certainly be swept under. It is sometimes possible to “swim” through an avalanche, but swimming in an avalanche is not a skill the average victim will have.

An avalanche typically contains many hundreds or thousands of cubic metres of snow, and the snow consistency is often heavy once it settles. One cubic metre can weigh 500kg, so if you are under an avalanche that has settled you cannot normally lift yourself out of the snow. You would need to dig your way out, and that could well be through a substantial layer of snow. It may not even be clear which way is up. Your best chance of survival is that someone else is able to dig you out – assuming they know where to dig.

Even if a skier is conscious and knows which way is up when they have found themselves under an avalanche, the snow will likely encase them such that they are unable to move. The air pocket around their face will be unable to sustain them for more than a short period, perhaps a few minutes. 85% of avalanche deaths are due to asphyxiation.

The impact of the avalanche may well have made the skier unconscious or caused serious injury. In 15% of avalanche fatalities trauma is a factor. Avalanches often include debris such as trees and rocks, and in turn may sweep a skier on to rocks or other hard objects.

If a victim of an avalanche is not killed by the impact and is dug out within 5 minutes there is a 90% chance of survival. If they have been able to create a large enough air pocket a survival time of an hour is possible but is rare.

I have talked in an earlier article about how important it is to have some form of beacon, such as a RECCO reflector, in ski gear to improve the chances of being found. If you do survive an avalanche, it is likely because of some one else’s preparedness.

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Avalanche Fatalities

WSL Institute for Snow and Avalanche Research SLF , 4.02.2021

Although most ski lifts have remained open in Switzerland during the Covid pandemic, more skiers and snowboarders than ever are choosing to go back-country skiing. Inevitably this has led to a record number of avalanche fatalities, with the number of fatal incidents this season to date more than any previous season this century. The season average is 22 fatalities, whereas this year there have been 17 already – and notably that also represents 17 separate incidents.

Fatalities by risk factor

A handful of fatalities were from skiing off-piste, i.e. using lift-served unmarked routes, but the majority of the deaths in Switzerland have been back-country skiers and snowboarders. One would generally expect these people to be better prepared than those killed off-piste. Four of the back-country fatalities occurred when the avalanche risk was moderate. These include one in the Jura, the first avalanche fatality in this area that I am aware of in over 20 years.

One off-piste fatality of a British skier occurred below les Attelas in Verbier on 18th January when the avalanche risk was moderate. This is generally considered a ‘safe’ off-piste area, bounded as it is by lifts and groomed runs. As is usually the case, the unfortunate skier was not alone, and other people were also caught by the avalanche but survived.

Interestingly very few avalanche fatalities (3%) historically occur when the avalanche risk is high and none when the risk is very high. The majority of deaths occur when the avalanche risk is considered considerable (65%). For people going off-piste an even higher proportion of fatalities occur when the risk is considerable.

Not surprisingly the majority of fatalities occur in Grabunden and Valais since these cantons are most popular for back-country touring and off-piste. However this does not mean other areas are safe. To add to the fatality in the Jura, there was also a fatality this season in Rochers de Naye amongst a group of young skiers – this in a pre-Alpine ski resort above Montreux.

The message to me seems clear. If the risk of an avalanche is considered anything more than moderate even well-prepared back-country outings would be well advised to abandon their plans. However 30% of fatalities occur when the avalanche risk is moderate (and 2% when it is low), so the advice is to thoroughly plan back-country expeditions and off-piste runs even in these conditions.

It is worth adding that every year there are also fatalities amongst other winter sports enthusiasts, typically a couple of snowshoe walkers a year die in avalanches. Additionally over 90% of avalanche fatalities are triggered by the victims and their companions.

Switzerland has the most sophisticated avalanche-warning system in the world, largely due to the sheer scale of the detection capabilities the SLF (Institute for Snow and Avalanche research) has at it’s disposal. However risk to an individual skier or snowboarder needs to be augmented by an assessment of the specific conditions the skier or snowboarder finds themselves in. It is the case that even pisted, patrolled runs can be hit by avalanches.

Many back-country skiers are well-prepared for the risk of avalanches, but I believe even resort skiers should be aware of what contributes to avalanche risk, and inspect the terrain they ski through, on or off-piste.

My golden rules are PRICK:

  1. Plan. Decide in advance where you are going and what risk factors may apply. Discuss with your party in advance in which circumstances you would change your plan, e.g. because of a perceived avalanche risk. Ensure you know where you are going and discuss rendez-vous points. Make a note of distinctive features on your route so you can accurately communicate where you are if you need to.
  2. Risk Assess. Check the current avalanche risk assessment for where you are going. Be aware conditions may deteriorate during the day.
  3. Inspect. Before you set out make an assessment of where you are going, visually and taking advantage of local knowledge. Whilst out, look above and around you throughout your day for higher risk features – rocky outcrops and corniches, broken branches on the uphill side of trees and other evidence of previous avalanches, particularly steep (30-45%) or convex slopes…
  4. Choose. Choose your route according to the above factors. If in doubt choose the safest option. Don’t get drawn into the ‘incident pit’.
  5. Kit up. Have the right kit with you. For off-piste, having a working phone on you and RECCO reflectors is a minimum, but equipment required for back-country may also be appropriate for more challenging off-piste conditions. For back-country, tranceivers, probes, shovels and appropriate training are considered essential, and airbags are recommended.

For those not familiar with the RECCO system, it is a very small battery-free transponder, frequently found in ski clothing and backpacks but which can also be purchased separately and attached to helmets, boots or ski jackets. In most resorts rescue teams can detect the presence of a RECCO reflector within around 200m.

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Avalanche Prediction Engine

Skitourenguru .ch is a fabulous resource that provides avalanche information based on a machine language model. Is is not perfect, but avalanche prediction will probably never be an exact science. In the meantime it provides ski touring enthusiasts in the Alps and Jura a huge amount of useful information.

The main focus is Switzerland, but the web site has become a go-to resource, with tens of thousands of active users and over 1000 ski tours covered from Switzerland alone.

Twice a day the site is updated with data from the authoritative SLF and uses daily avalanche forecasts from the past 19 years, covering over 5000 avalanche forecasts augmented with data on 1,800 severe avalanche accidents and 50,000km of GPS tracks from actual backcountry ski tours.

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Avalanche Risk

Eight people died in Switzerland over the weekend from avalanches, and several others have been hospitalised according to a report from SwissInfo. Seven of a party of nine on Piz Vilan in Graubünden (just North of Grüsch) were caught by an avalanche, of whom
five died. Avalanches also killed a 28yo snowboarder in Mürren, a 31yo skier in Adelboden and one of a party of three in Wildhaus, Toggenburg. Two lucky skiers in Verbier were rescued after being hit by an avalanche. However three other people died in avalanches last Thursday and Friday, bringing the total fatalities in just three days to 11 in the Swiss Alps alone. Needless to say the avalanche risk is very high, but the level of fatalities is concerning – especially as many of the victims appeared to have been well experienced winter sports enthusiasts well-prepared for off-piste conditions.

The Institute for Snow and Avalanche Research (SLF) publishes avalanche information and the map from this morning indicates just how dangerous the Alps are after the recent heavy snowfalls.
SLF Avalanche Risk
Personally I would not go outside the boundaries of marked runs anywhere at this time, but – with sufficient planning and caution – it is possible to reduce the risks of being overcome by an avalanche to near zero, even if off-piste. Indeed, it is worth bearing in mind that fatalities do occasionally occur on piste from avalanches (and in 1999 31 people were killed when the ski resort of Galtür was hit by an avalanche); knowing the level of avalanche risk and the risk factors is worthwhile even for people who do not stray off-piste.

The first consideration concerns nearby slopes as well as those you want to ski on. The overwhelming majority of avalanches occur on slopes with a gradient of greater than 35% but they can occur on slopes with a gradient of as little as 30%. Even on-piste, I tend to stay on the side furthest away from such unprepared slopes if the avalanches risk in the area is rated considerable or higher. It is also worth watching out for skiers or snowboarders traversing high on such slopes – the line that the skiers and snowboarders take can weaken a slab and initiate an avalanche. Indeed, the very presence of others skiers or snowboarders above you and off-piste is more likely to indicate heightened risk rather than relative safety since many avalanches are triggered by freeriders.

The sun helps the snow on slopes to bond, so periods without sunshine or of little sunshine, such as mid-winter, or periods of heavy snowfall and north-facing slopes tend to be associated more often with avalanches. On the SLF charts, the more avalanche prone slopes are indicated black on the compasses on the SLF chart – as the chart above shows slopes facing all directions are currently prone to avalanches. In addition wind-blown snow can often create dangerous drifts and this is more likely to happen above the treeline and at higher altitudes in general – again the SLF chart indicates that avalanches are more likely above a given altitude. The SLF will also identify whether wind-blown slopes, gullies, bowls and areas adjacent to the ridge line are particularly risky over and above the general level of risk associated with an area.

Clearly skiers and snowboarders should be prepared for off-piste conditions, with transponders, probes, shovels, ABS and cellphones amongst the minimum for back country outings, but it is a false sense of security to believe that these will be of any help in many avalanche situations. The trick is to avoid putting yourself at danger, and the signs at this time are to proceed with extreme caution, avoiding off-piste in all but the most benign circumstances.

At least the latest snow redresses a situation which left many runs patchy and off-piste snow depths often too limited to cover obstacles such as rocks and tree stumps. In the Vaud Alps well over one metre of snow has fallen in the last few days, and most of the rest of the Swiss Alps and the Western Jura have experienced up to a metre.

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