Decision Making in Avalanche Terrain: Pt.II - Friends and Family
- Henry
- Apr 23
- 8 min read
Updated: Apr 23
What does avalanche decision making actually look like in practice?
In this special three part series, I review three incidents that sparked conversations about avalanche safety, in my head and amongst my friends, when out on the slopes.
By breaking down these episodes, we can learn much about avalanche safety; but, perhaps more importantly, we can begin to understand what decision making in avalanche terrain actually looks like, something we're told to do in avi courses but may not have the tools to do straight away.
Introduction
Shortly before we witnessed our group of strangers pick their way up the ridge high above Pays Desert, my friends were caught in an avalanche themselves. A comparatively small affair, three people were caught and carried, and my friend’s partner was fully buried; she was dug out minutes later, and, thankfully, everyone was okay.
The incident has sparked an ongoing discussion about avalanche safety amongst my friends. We joined him the following week and skied in the same part of the world and, after some run-ins with avalanche safety over the previous years, this was the driver we needed to really move through the gears and bring some stuff out into the open that previously we had assumed or inferred.
As a result of these conversations, our learning, planning and decision making in the backcountry was better than ever. And it started with this first incident. So let’s go all the way back to this avalanche, measure it up against the four factors that we know influence avalanche behaviour, and find out what we can learn from this experience.
It’s important to note that I am not an avalanche professional. I do not investigate avalanches, and it is not my job to cast judgement on those involved or their actions. These, more than anything else, are just my personal thoughts, how I chew over incidents, and, more than anything else, how I continue what is a never-ending and still embryonic journey through my own avalanche safety. It should be taken as nothing more than an inner monologue and with more salt than a soup spoon of ocean water, but, hopefully, it might make you begin to ask similar questions about avalanche safety and your decisions in the backcountry.
The Incident
A group of seven skiers were traversing along a series of bowls to access an off piste route in Val d’Isere known as Grand Vallon, led by a pair of experienced skiers one who was respected for their knowledge of the area and off piste skiing in general. These two skiers waited at the end of the traverse, below the rest of the skier, on an island of safety, aware that the traverse across is known to be an avalanche risk area. As three skiers clustered together on the traverse track, partly due to perceived pressure to speed up from a trailing group, a small avalanche of D1 size, roughly 30yds wide, 20yds in height and 3ft deep, slid down catching and carrying the three skiers. One skier was fully buried, but extracted moments later by the same guide of a trailing group close behind.
Terrain
The avalanche took place in an area known as Vallon; skiers familiar with Val d’Isere will know this area well. It is an area of off piste skiing that is well known for its excellent powder reliability as well as its accessibility, requiring a traverse across from the resort boundary (such as it is in Europe) to access any number of skiable bowls.
These bowls are, however, known avalanche risks. Generally, they are all north facing and, thanks to a quirk of geography or something, generate fairly strong snowpacks meaning the bowls themselves rarely slide. But further down the hill, as you approach to rejoin the pistes just beyond the Fornet Gondola, they become more exposed to the sun – one of my earliest pieces on thinking about avalanche safety was exactly in this sunny spot further down the hill.
The face itself bends round from a generally north facing aspect to a north-west facing slope, just on the face on which the avalanche occurred. This will be critical later on. Similarly, the slope angle doesn’t look that steep, but kicks up towards the end into something that is probably just, just over the magic 30° angle we need for avalanches to kick off at.
To be honest, I wouldn’t have been very concerned about this when skiing over it myself. This drives home the dangers that avalanches can pose, particularly the idea that, sometimes, avalanches do just happen. They can occur on slopes of less than 30°C and on comparative islands of safety, so it is important to remain defensive until you know 100% that you are in safe territory.
Snowpack
A few days later, my friends and I dug a snow pit on a similarly north facing aspect of the mountain a little further up the hill. What we found was incredibly dull; a strong, consistent snowpack the started soft at around pencil or knife firmness (we didn’t have a pencil or knife to confirm), that transitioned, without clear delineation between layers, down to a firm, fist-strength pack just beyond a metre down.
This was an ideal snowpack for skiing on. There where no weak layers to speak off, and even the powder at the top was compacting into the pack as the day went on. This was an incredibly secure snowpack showing very little signs of weaknesses that contribute to avalanches. Even more so, this pit would have been almost identical if we had dug it on the site of the avalanche.
Almost.
There are two key differences that would have elevated the avalanche risk at the avalanche site compare to what we saw in Pays Desert. Whilst elevation was (remarkably) identical, the aspect of the slope and the wind loading that had taken place over night were different.
The angle at which the avalanche took place was twisted from true north ever so slightly round to north-west. This meant that the last of the evening sun would have hit it, and softened it up, possibly creating something like a corn effect on the surface.
Temperatures then plummeted overnight the day or two days before the avalanche, especially before the avalanche hit, freezing this now-watery snow into a layer on which snow can slide and create avalanche conditions.
Weather
The second aspect here falls under weather, as it is an immediate cause of the avalanche rather than a long term influence. My friend sent through a picture of the avalanche with the caption “only had 10ish cm overnight”.
The “only” is doing a lot of heavy lifting there. 10cm is more than enough to elevate avalanche conditions and, critically, snow had been laden on this face by a strong overnight wind.
In the picture, there are clear signs of wind loading – there are waves on the surface of the snow, and the snow has taken on a grey-ish hue that is a unmistakeable sign of having been moved around by the wind. Whilst 10cm may have fallen overnight, far more than that could well have been sitting on this overnight frozen crust ready to slide.
Thus, from a benign slope that you or I would have no qualms crossing, through an almost perfect series of unfortunate events, we now have a recipe for an avalanche.
Human Factors
It's really easy to look at all of the above and simply ascribe this to bad luck - being in the wrong place at the wrong time. But peel back the layers and there is a lot more going on here, especially when you consider the human factors in play here.
Human factors are a combination of different things that impact our ability to make decisions; or, perhaps, something woolly and irrational to explain why we might make irrational decisions when we've tried so hard to distil everything down with rationality.
This is a really great example of how these factors play over and around each other to cause this incident, perhaps far more than pure bad luck. Let's dive in.
There is a really clear example of expert halo at play here. My friend and his family have been skiing in Val d’Isere pretty much all their lives, he completed a season here not too long ago, and his brother who was in the same group did one last year. They were skiing in a reasonably sized group, were following a pre-existing traverse track, and were being followed very closely by a group led by a guide along the same path.
However, there were varying levels of off piste experience in the group, some only skiing off piste for the first or second time, and the presence of the guide behind, the well-worn traverse track and the skiers in the group familiar (although not current) with the area meant that everyone, to some degree or another, put aside their own awareness of the conditions and trusted someone or something else to have made those decisions for them.
Planning for this route could also have been improved. I mentioned above that the group was familiar but not current; they had skied this line many, many times in the past, often with myself skiing with them of late, meaning they are familiar with the terrain and how the snowpack varies throughout the day and the winter, but this was the first time for all of them this season; therefore they were not current with the route. This means being aware of snowpack depths, changes in terrain and changes in avalanche risk that may or may not be different from previous years.
The mix of experience mentioned above also played into another factor; peer pressure. Some members of the group were only skiing off piste for the first time, and the group as a whole were experienced off piste skiers who knew the area and, importantly, regularly chose to ski off piste as their preferred form of skiing. Coming into this group should have required a big step off the gas for the group, to slow down with their planning and communication; this didn't happen. Instead, lesser experienced members felt pressured to ski this line, straight away at the start of the holiday, despite barely knowing how to turn on a transceiver.
The avalanche risk for that day had also indicated increased risks due to wet snow and wind laden snow on generally northerly aspects. Thus, whilst there is a large element of pure bad luck on being avalanched, caught, carried and buried in this way on this particular slope, this had been noted in the avalanche forecast that this particular slope might act in this way. Whilst the avalanche risk remained low - a 2 out of 5 (moderate) – there is still the risk of particularly human triggered avalanches, which the group discovered on this day.
Finally, the group was not best organised to either prevent such an incident happening, nor to mitigate the risk. The two skiers who set off first were experienced skiers, with avalanche safety skills and knowledge, who knew that the terrain was an avalanche risk.
One of the other two experienced skiers was halfway between the safe zone and the slide. Two of the three skiers who got caught were unfamiliar with protocols for crossing avalanche risk terrain, and had bunched together when they should have been keeping a good distance apart, possibly directly contributing to the slide. Whilst the experienced skiers in the group had done their utmost to communicate the risks of bunching in avalanche risk terrain, it was clear this message did not get through - it was communicated too late, and not clearly enough to be understood in time to prevent the avalanche.
Furthermore, when the slide did occur, three out of four of the experienced skiers were unable to return to the site of the accident to assist, whilst the other was involved in the slide; they were hidden from the view of the incident in an attempt to remain in an island of safety, and as such did not even know the slide had taken place!
Final Thoughts
This incident went on to inform a lot of the discussions and decisions that my friends and I took later the following week, when we went touring and backcountry skiing. One thing that we took from this incident, and previous incidents, was communication; we all know we know avalanche safety, and we all know we all know we know avalanche safety, but we have been poor in the past at communicating what we know and that we know we know. This, in many ways, was this taken to the extreme. Mix this with a group of varying abilities and experience, with a springling of peer pressure, expert halo, and assuming everyone knows what they're doing, and you have a recipe for disaster.
Whilst the inference of avalanche safety may well be there, it is how this is communicated amongst the group where this is critical.
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