Thursday, 25 February 2010

Extreme Avalanche Hazard in the Hills

Following significant heavy and wet snowfall on to a thick layer of surface hoar there is now a a very large risk of avalanche across much of the Scottish Hills. This is clearly demonstrated in this photo from the SAIS.

Please follow the SAIS links on the side bar to see the avalanche forecasts.

The following explanation was posted on the UKC Winter Climbing Forums by one of the SAIS forecasters during a discussion on categorizing avalanche risk and illustrates the seriousness of the current risk.

"Just for the record, a ‘Very High’ hazard of avalanche category has never been used in Scotland since the inception of the SAIS (or Scottish Avalanche Project, as it was called when it began in 1988). There were probably only a few occasions prior to its beginning when conditions may have warranted a ‘Very High’, but these are now of historical interest only (The Loss of Gaick – twice! – when a substantial building was overwhelmed and demolished by avalanches 100 years, to the day, apart).

All countries with seasonal snow cover interpret hazard categories according to local conditions. In Europe, the Swiss, in particular, require a scale with a pretty serious top end because they have densely populated villages in high Alpine locations that can be wiped out by avalanches (many villages destroyed in the 1950s). Same applies to the Austrians (most recently, Galtur), the French (eg. Montroc) and the Italians (eg. Cervinia).

In Scotland, our problem is one of recreational visitors (climbers, hill-walkers, ski-tourers) and the massive frequentation of these hill-goers during the winter months. We tend to extend the scale upwards. For instance, in Canada I was a little taken aback, when I was on training and assessment there, at how the Canadians viewed the size and frequency of their avalanches in relation to the hazard category. Avalanche frequency/size and stability that I would happily have called Considerable if I were working in Scotland were unanimously designated as Moderate.

The North Americans have more and bigger avalanches; we have fewer but way more visitors to the mountains. (Scotland had more avalanche fatalties –12 - in the winter of ’94-’95 than Canada). My guess is that we unconsciously slew the scale upwards to take account of this high level of frequentation and our terrain/topography. Most of our avalanche victims don’t get fully buried. Many suffer trauma injuries ‘in transit’ down the mountain by getting banged in to rock, boulders etc. Complete burial is more common (sometimes with trauma) in Alpine nations. Bottom line is that Scottish avalanches don’t have to be big to kill you. Get caught by a small slab, lose your footing and take a 300m tumble down a crag will have much the same ultimate outcome as a full burial under a couple of metres of avalanche debris.

Today there was some discussion as to whether or not to put out a ‘Very High’ category for tomorrow (Friday) on my patch. At least one other avalanche forecaster out the 5 SAIS areas has discussed this possibility with the SAIS Co-ordinator within the past day or so. Instability is certainly widespread at the moment (a ‘Very High’ pre-condition) and not just confined to a few aspects. The avalanches are also likely to be big ones with long run-outs (another ‘Very High’ pre-condition). My own issues are with the exposure of a low-level and popular approach path to big avalanches from above. This happened a couple of years ago when a big one passed through open and mature woodland, took out a few trees (root-ball and all) and crossed the path. It was decided today that the ‘High’ category covered this contingency but that our use of the ‘Very High’ category would be reviewed as conditions develop."

Today we stayed safe and climbed at the Ice Factor and Onich Slab. I was running a Climbing Improvers / Everest Preparation course for Adventure Peaks

'Wet' Tooling at the Onich Slab

Training for the fixed lines on Everest