Rockfalls as a hazard to mountaineers in high mountain areas – GWC Mag

The Landslide Blog is written by Dave Petley, who is widely recognized as a world leader in the study and management of landslides.

Rockfalls are a key risk to climbers in high mountains, potentially causing injury or even loss of life. We regularly record such events in our fatal landslide research, although I have always suspected that we do not capture these events adequately.

In recent years there has also been concern that the degradation of permafrost in the Alps resulting from anthropogenic climate change may be making climbing more perilous, of which more below.

A really interesting paper (Benedikt 2024) has just been published in the journal Heliyon that looks at this issue in more detail, focusing on data from the Swiss Alps. The dataset is the records of climbing accidents that have involved rockfalls, collected by the Swiss Alpine Club between 2009 and 2020 inclusive. The dataset covers many of the main climbing areas in Switzerland, and provides the following information:

“all rescue events where mountaineers require professional help of mountain rescue services. This also applies to events such as illnesses and evacuations of mountaineers that are not injured. Each mountain emergency includes the emergency number used, date, rescue organization, event, place, canton, activity, NACA (National Advisory Committee for Aeronautics Score) score, nationality, birth date, sex, place of residence, coordinates, and a case report”

The author has focused on events that involved a rockfall in some way – in total there are 266 events in the dataset.

This is a very rich study. Some aspects are fascinating – for example, the sex of the victims was 210 male and 56 female, which probably reflects the population of high altitude mountaineers. The average age of the climbers involved was 50 years, which is older than I might have expected – I wonder if this reflects the age split of mountaineers, or indicates that older mountaineers are more likely to need rescuing?

There is a strong seasonal pattern in the data:-

This reflects two aspects, I suspect. First, we know that rockfalls in high mountain areas are seasonal, mostly occurring in the summer months when permafrost melting is most likely. But second, the mountaineering season is also strongly seasonal, with many more mountaineers in the summer months, so vulnerability also increases at this time.

Intriguingly, there are two perhaps slightly surprising results over the study period. The first is that the number of recorded events per year shows no trend – it has remained constant at an average of 22 cases per year, one or two of which are typically fatal. Given that mountaineering as an activity is growing at an estimated 4% per annum in Switzerland, this implies that per capita risk is actually reducing. The second is that the severity of the emergencies has also slightly reduced with time – in other words, when a mountaineer suffers a rockfall accident, the injuries are becoming slightly less severe.

Even in years in which high rates of permafrost degradation were recorded (e.g. 2017 and 2018), no notable increase in accidents was noted.

So what is going on here? Well, Benedikt (2024) correctly points out a number of key aspects to consider. Safety standards in mountaineering have improved over the period of the study – for example, the use and quality of helmets, which may reduce both the frequency of accidents and the severity of injuries. It is likely that a portion of the rockfalls that cause injuries were triggered by other mountaineers higher up the slope, but increased awareness of the risk might mean that such events are becoming less common. And the age profile of the victims might mean that we are considering a risk averse population that is actively managing their vulnerability. So, for example, people may be choosing not to climb on days with high rockfall hazard.

This is a really good study, and I think there are some very interesting opportunities to interrogate the data further. It would be particularly interesting to integrate the data with quantitative studies of rockfall activity and permafrost degradation to understand the relationships, and of course to extend the analysis to other areas.

Finally, it would be interesting to see how the data looks for the 2022 mountaineering season, which was severely impacted by rockfall hazard. Climbing in the Alps in 2023 was also severely impacted. Of course, if there were no mountaineers in the peaks when rockfalls occur then the risk was zero, meaning that the data will need careful analysis.

This is a fascinating study about a key aspect of the risk from landslides. I hope we’ll see more studies of this type.

Reference

Benedikt, G. 2024. Rock falls while high-altitude mountaineering – More often in the last years? Evidence from the Swiss Alps. Heliyon, 10 (3), e25413.
https://doi.org/10.1016/j.heliyon.2024.e25413.

Text © 2023. The authors. CC BY-NC-ND 3.0
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