Kwam zojuist dit recente filmpje met nogal rijkrekenende analyse tegen:
De video is inmiddels ingesteld op prive. Hier staat de (verkorte) video nog wel: http://www.skipass.com/news/113886-avalanche-a-sainte-foy.html...
This video is about Foglietta North Avalanche 5 Jan 2015, Ste Foy Tarentaise, France
This video, taken by my friend Liam, is not only shocking to look at, but it offers some really good education for all of us. Here are some facts and observations below - please feel free to comment.
6 people in the group; 5 people taken in the avalanche; 3 partially buried, 2 totally buried (under approx 30 cm); Avalanche released when the 5th person was skiing. 3 people injured needing medical attention e.g. broken bones and torn ligaments; 1 person spent 4 days in the hospital.
Slope Aspect: North
Slope Steepness: approx 30° at point where the 5th skier was at time of release (approx 35-45° at crown)
- distance width: approx 450 m at top
- depth (average approx): 20-40 cm (deepest point ?)
- altitude (average approx) at top 450m of crown: 2915
Avalanche flow distance: 2925 m - 2500 m approx vertical
Distance the 5th person travelled in the avalanche (the longest ride of victims) : 372 vertical metres traveled (2908 m to 2536 m); approx 1.2 km total distance
Snowpack summary: windblown powder on faceted grains
Interesting observations and education
Sound of the snow: You can hear the collapse of the weak layer (or 'rupture' as A. Duclos would say!) about 1 or 2 seconds before you see the slab moving. Also notice the hissing sound of the snow as it flows by after the avalanche has released (this is the sound of 'faceted grains' sounds a lot like skiing through facets or 'loud powder').
The avalanche released while the 5th skier was going: It's often the case that slab avalanches do not release on the 1st person
Islands of safety are relative to the size of an avalanche: The safety point where the 4 first people gathered was not big enough to protect the group from this big avalanche. The danger rating of 3 on that day forecast basically says that if an avalanche were to release it would most likely be a small 'isolated' or 'localized' slab. The size of this avalanche is large - perhaps more consistent with an avalanche danger rating of 4. In sum, in my opinion, that island of safety might have been perfectly good for a 'localized' or 'isolated' slab, but obviously not for the large one that released in this case. We all need to anticipate, 'what if it goes bigger than I expect!"
Current conditions: Perhaps most importantly, this type of incident give us all a good, clear clue of what the snowpack stability is like at the moment of the avalanche. We can apply that to our own skiing, walking and climbing in the following days (even weeks) as new precipitation and wind adds increased accumulations (weight) onto the existing snowpack... and the potential consequences of getting caught up in one of these beasts!
Search and Rescue: Liam made the point that it was important that everybody was able to be autonomous in the search phase. For example Liam was at the top of the avalanche when he started the search while two other members of the group were at the bottom close to 1km away. While he was doing a 'signal search' at the top he was too far away from the searchers below to communicate with them. So everyone had to get on with the search and rescue more or less on their own: choosing what they should be doing and executing without waiting for someone to tell them what to do (from what I understand, the searchers found the buried invdividuals at the end of the 'coarse search' at about 1-3 metres from the victims - before they had to do a fine search and probe - this underlines the importance of looking for visual clues even once a good signal has been found). The fact that everyone in the group had avalanche transceivers, and had practiced with them, was crucial in what ended up being a speedy rescue (the buried individuals were found in 15-20 mins approximately)... Also worth noting that one digger dug out both victims before the helicopter arrived. As Liam said (and two other professional friends of mine have said recently), 'you need to be able to deal with everything yourself!!'
* bericht heb ik aangepast met nieuwe link naar de video op skipass.com