Catégories : environnement montagne

Type d'article : individuel (CC by-nc-nd)

Testimonies

For this latest edition, we selected and analysed two reports of spontaneous avalanches that affected climbers on icefalls. In both cases, the risks had been assessed and certain warning signs could be identified up on the mountain. But the fact that the outings were going so well, the protagonists’ high level of motivation and a number of “deceptively” reassuring factors meant that their awareness of the hazards they faced that day was not adequately translated into tangible adaptations.

Report no. 1 - Razis Crévoux icefall : Detailed description

An avalanche of heavy snow was triggered on the slopes above the Razis icefall at around 3pm, sweeping down the left-hand side of the central section for around 2 minutes and completely burying two climbers who were setting up Abalakovs at the foot of the ice wall. The deposit zone was 5 metres wide, 10 metres long and around 2.5 metres deep at its highest point.

Around thirty people were on the mountain that day: two groups of around ten climbers, each led by guides and instructors, a few self-guided roped parties, and a group of around ten unsupervised climbers, including myself.

When we arrived at the car park, it looked as though the routes were going to be busy that day, but by the time we had finished the approach hike, we realised that everyone had enough space and the general mood was upbeat. We were able to exchange ropes. All the routes were equipped. The ice was good, the temperatures were still sufficiently negative deep in this valley, and our general level of ability roused our competitive spirit.

We had read the avalanche bulletin, which announced a risk of “3, all exposures”, but the route description only mentioned the risk of avalanches on the approach and nothing at the icefall. Indeed, from below one could clearly see snow purges in the various gullies that line the route, but the fact that the icefall was some distance away and in a different zone led us to believe that the area would not be subject to any such purges. As a result, we left all our safety gear in the car, which we sometimes do on outings that we consider “safe”...

We saw a few spindrifts of snow along the way, in the woods overlooking the icefall, and these accompanied the climbers throughout the morning. We laughed about this, because it made the climb more interesting.
As midday approached and the sun reached the top of the icefall, there were a few small avalanches, probably originating from the trees. Nothing to worry about, but we thought we should get a move on.

At 2pm, an avalanche was triggered to the left of us. It was larger than the others, but very brief. I heard someone in our group say “let’s get out of here”. But the group effect (...) prompted us to keep going.
At 3pm, I decided to leave (…). There were more small purges of heavy snow.
We descended along the riverbed, then suddenly we heard a loud, intermittent roar. We turned round just in time to see a stream of heavy snow tumbling down from the top left-hand side of the icefall (...) as if the mountain were being flushed out. There was silence and then the first cries.
(…) Damn it! We hadn’t brought our transceivers, shovels and probes – how stupid!...

The remainder of the account describes how the rescue operation was organised, using shovels and probes that members of the other group had been sure to bring with them. In the end, all those who had been buried had one hand sticking out of the snow and were able to be quickly freed. (…)
In the heat of the moment, I felt a great deal of anger. I was furious that I hadn’t heeded the signals, but above all I was angry that I hadn’t brought all the essential safety equipment with me, because we had mistakenly thought that it would be safe. That was a real rookie error.
Among us were guides, instructors and climbers with a decent level of ability, and no one thought it would be a good idea to carry a transceiver. How could so many of us have been fooled in this way? Was it group influence, cognitive bias?

If we had to learn one lesson from that day, it would be this: always carry your avalanche transceiver with you, along with a sturdy shovel and a proper probe. Take rescue training and, above all, learn how to ORGANISE a rescue, because in this instance we were anything but organised. Of course, it’s easy to say all this and give lectures after the event, but given that this is such a textbook case, it’s important that we question ourselves and avoid it happening again.

Route analysis

We had originally planned to go to Cervières. At breakfast that morning, the plan changed and we decided to go to Crévoux, as it seemed more accessible in terms of the level of difficulty. We quickly checked the route description. We found out after our outing that an avalanche had been mentioned in previous reports, but we hadn’t taken the time to read them all as we usually do.

Level of awareness and assessment of the risks

The group effect had a very negative impact on our assessment of the risks.
A number of factors should have alerted us, in addition to the level 3 avalanche risk on all exposures :

• The advancing hour.
• Purges that began small, but which became larger and larger.

While a beginner would easily have spotted the red flags, this more experienced group became caught up in their own momentum. They may have thought that it was fine to keep going and that there was no risk, since the location was reputed to be safe.

Report no. 2 - Les hémos à Godo : Detailed description

Having gone a while without an outing, we decided to tackle a classic route in the Vallons du Diable: Les hémos à Godo. The alarm went off at 4.30am. It was easier to get out of bed than anticipated, which felt like a good omen. Conditions at the icefall were good, according to the latest reports posted on CamptoCamp.

(…) Arriving at the icefall provided a moment of joy. We geared up, divided up the equipment and set out our roles. X1, who was feeling particularly motivated on this fine Saturday, took the lead at the start of the route. The climb up the icefall went quickly and smoothly (...) It was at this point that we heard it. The calm of the snow-covered mountain was replaced by a loud rumble, like the sound of a drum being pounded at a high tempo. (…) A second later, the source of this noise appeared: a torrent of snow, like a terrifying wave emerging from the top of the rise. (…) I was fortunate enough to be at the foot of the rise and the steady flow of snow only hit my backpack. Guided by a primal survival instinct, I decided to traverse a few metres to the right. I knew that the steepness of the icefall would protect me. I made it with ease in a matter of seconds. I was now inside this raging cascade. (…) Then, after twenty, thirty, forty seconds, everything stopped. The noise ceased and daylight returned. I had only one thought: what had happened to the others? X1 was above me, the sight of the wave of snow crashing down having left him with only one option: to jump and take refuge in the vertical section. X2 was also safe, he had probably felt the force of the falling snow the most. Even though his belay was slightly offset, he had been hit by some of the avalanche. Luckily, the belay hadn’t been ripped out. It took us a few seconds to come to our senses. At that point, there was only one thing to do: get back to the belay and descend as quickly as possible. (…)

Conditions

Examination of the avalanche risk bulletin: in hindsight, our analysis had been inadequate. Thursday’s strong winds were not properly taken into account and the same could be said for the poor refreeze on Friday night.

Level of awareness and assessment of the risks

We had assumed that there wasn’t enough snow for an avalanche to be triggered. In hindsight, I think we had greatly underestimated the strong winds on Thursday and the poor refreeze overnight. I would say that the incident stemmed from a misinterpretation of the avalanche risk bulletin and perhaps from us telling ourselves that it would be fine.

Analysis

This analysis highlights the most significant factors, while also making reference to reports of other incidents and known decision-making biases. Our aim is not to imagine retrospectively what could have been done to prevent the incident, nor to pass judgement on a situation that any individual might one day face. Nor will we comment on the conditions on the ground that day (snow conditions, ice conditions, weather, the potential for rock or serac falls), but rather on the risk assessment conducted and the behaviours of those involved. Our objective is to highlight all the key points and, if necessary, to suggest ways in which similar situations could be better managed.

By Maud Vanpoulle high-altitude mountain guide and accidentologist
Reviewed by : Olivier Moret (Petzl Foundation).

Key points and food for thought

Reassuring factors

In both of these reports, the participants mention reassuring factors that seemed to obscure any information or warning signs that might have jeopardised the outing’s completion. Such reassuring factors steer attention solely towards positive signals, thus reducing the vigilance of participants and ultimately hindering a more clear-sighted analysis of the risks. In the first account, danger signs had indeed been identified, but the determination of other roped parties to continue, the general competitive spirit at play, and the feeling of “so far, so good” encouraged the group to keep to the plan.

Attention focused solely on positive signals

Various analyses have shown that attention tends to be focused primarily on positive details or on minor but encouraging signals, even if they have little bearing on the main risk identified. The goal of successfully completing an outing often blunts our clarity of mind when faced with a risk that can be identified thanks to a few tangible clues on the ground.

Report no. 1 “When we arrived at the car park, we thought the various routes were going to be busy that day, but by the time we had finished the approach hike, we realised that everyone had enough space and the general mood was upbeat. We were able to exchange ropes. All the routes were equipped. The ice was good, the temperatures were still sufficiently negative deep in this valley, and our general level of ability roused our competitive spirit."

Report no. 2 “Arriving at the icefall provided a moment of joy. We geared up, divided up the equipment and set out our roles. X1, who was feeling particularly motivated on this fine Saturday, took the lead at the start of the route. The climb up the icefall went quickly and smoothly.”

Social proof or group competitiveness are highlighted in 9% of SERAC reports. The cognitive bias known as “social proof” results from the tendency to interpret behaviour as safe when it is displayed by others. “If they are doing it, then that behaviour or decision is reasonable.” This bias is reinforced if other individuals present are perceived as competent or legitimate (e.g., a professional). “The competitive spirit at play here seriously hindered the assessment of risk.”

The fact that a route or section is reputed or perceived to be easy or relatively safe can lead to reduced vigilance.

This is a factor that is highlighted in 44% of SERAC reports and which seems to have had an influence on the situation at the Crévoux icefall: “While a beginner would easily have spotted the red flags, this more experienced group became caught up in their own momentum. They may have thought that it was OK to keep going and that there was no risk, since the location was reputed to be safe.”
The reputation of a route that is perceived as being easy and relatively safe, that can be completed in bad weather or where there is a high risk of avalanches, can inhibit a reassessment of the dangers on the ground.

Feedback from the experience

The risk of avalanches on icefalls is underestimated

Icefalls form in the drainage areas that are often located beneath steep snow slopes. The latter are prone to purging after fresh snowfalls, or as a result of exposure to sunlight or rising temperatures.

The first precaution to take is to assess the likelihood of purges, not least by reading the avalanche risk bulletin at the route planning stage. It is particularly important to assess the risk of spontaneous avalanches. Once on the ground, it is easier to evaluate the quantity of snow on the slopes overlooking the route, the rise in the temperature and the time at which the sun will start warming up the snow.

The phenomenon of temperature inversion is deceptive: mountaineers tend to start their climbs in the icy shade of a valley floor, but the slopes overlooking the route may be bathed in spring sunlight and heat.

While wearing an avalanche transceiver and carrying a shovel/probe are very much recommended, one must bear in mind that avalanches channelled towards icefalls are powerful, devastating and offer almost no chance of escape.

We would like to thank the authors of this report for sharing their experience and for their willingness to engage in this critical analysis so as to help build collective expertise.