Monday, 7 December 2015

Uncertainty and Avalanches

TAR (The avalanche review) from the American Avalanche Association has some of the most insightful articles on avalanche education and psychology that I have ever read, as well as reviewing of what works and what doesn't in avalanche forecasting and rescue.  Folk are trying to grapple with another past (2015) season of serious incidents on both sides of the pond especially Europe, and understand why the majority of these occur in days of medium risk.  The key maybe simply uncertainty. Forecasting and avalanche risk assessment is about predicting based on past and future weather and therefore will always be uncertain and a game of probability. Past history may be accurate but weather forecasts are not. Couple this uncertainty with risk homeostatis from ABS and carrying avalanche rescue tools and folk then feel safer. Add GoPro Hero culture to the cocktail then the recipe for feeding the white room spin cycle is complete.



The top graphic is pretty obvious.There is a certainty that natural and human triggered avalanches are predicted above 650m on N to SE aspects and a localized risk present below this altitude from NW through South. Most folk with a brain will avoid the areas above 500m (allow a bit of leeway!) as RED is the colour of danger (obvious!) and will choose to go to safer aspects which in the above is green which as a colour gives the assurance of greater certainty. Things become less certain on yellow and very uncertain at orange. This uncertainty is where the risks are, and things become even more uncertain when the risks are localized. Yellow the probability of getting caught is less but still uncertain, stick a localized considerable orange strip in there and you have a mine field of uncertainty lying in wait for you to cross. You can't see the mines but can guess using the wind direction and slope shape as as to where hot spots of weakness might be (a guess - all be it can be an intuitive one but still a guess!) but you have to be very uncertain as you just don't know. Decending on ski's from above and you will likely be going too fast and not see the danger until your in the spin cycle and it's too late.

How do you mange or minimise risk if you have to travel on these aspects or choose to ski them? Well you don't manage the risk with any degree of certainty as you just don't know for sure where weak spots are, and you will for sure not know the true propagation risk from a trigger. You can't minimise what you don't know - so uncertainty!  And yet graphically on the above for the inexperienced person there is a temptation to look at these localized hot spots in the rose and think "I can avoid them", as surely I will recognize these weak areas and can ski/walk/climb around them. 

So my take on why it is that most folk get whacked when the risk is considerable or localized, is that being outdoor optimists (as we all are), and perhaps having got knackered climbing up a mountain or skinning in to a valley, or maybe having a bluebird pow day folk get used to that risk level as it's used the most  representing the most common and therefore familiar conditions for long periods.  And yet this risk level has the most uncertainty and therefore is the most dangerous for the winter sports person. Make sense?

I suppose if you were to roughly put a % chance of probability on the European avalanche scale you could say that:

Black 100% chance of getting whacked while either minding your own business in Galtur or being suicidal in Tignes

Red   98% chance of getting whacked on an aspect with that high level of risk and the Scottish equivalent of Black sometimes(apart from Gaick Lodge our main roads and villages are not in avalanche runout zones so Black does not apply)

Orange  the big problem (to me) be it slices of tray bake sized considerable, or isolated hot spot. If the rose is all orange then in my view its just the same as red but less obvious. You have a very high chance of getting whacked. Stick some localised Orange risk in among yellow then it becomes 50/50 and that's still scary uncertainty as folk think they can recognize the danger hot spots and avoid them. Maybe they can, but then maybe not. A low angled slope day for me, well away from run out areas.

Yellow maybe a 40% of getting away with it, but victim triggered death is still very likely if you hit a hot spot and it propogates into something big or is above a terrain trap.

Green well either its the best of Scottish neve and you should be climbing with blue skies, or get the lawn mower out in February.  If its the best of Scottish neve and its a sunless aspect then watch out as next time it snows as there's bound to be something growing on the top surface that will give a high risk when it snows next.

Having a blue bird day, or up for it then the glass half full person will go for it. Sadly they might end up with the glass all empty and smashed. It's a bit of a gamble and the more times you roll the dice the more chance you won't be needing your old age pension. 50/50 isn't odds, its worse than Russian Roulette!

Piss or get off the pot
The above americansim is pretty appropriate. Only one thing is for sure, we can only manage uncertainty up to a point. We live in a chaotic universe, bad things happen to good people and as mountain folks a lot of good things happen to good people as a reward for getting out there. I think we have to accept that the line between the best day skiing of your life and geting taken out is pretty close if you really want the powder days.  If you dont accept that then take up another sport.  We can reduce risk by managing uncertainty and reduce consequences by equipment and terrain choices, but in the end avalanche prediction and avoidance will never be 100% accurate. I am told knitting is pretty safe if you prefer a more sedate pastime with easier risk assessment.

Avalanche Types and Uncertainty
Some types of avalanche are more predictable i.e "certain" and some less so and some types of avalanche risk can be more easily seen in tests and observations. The ones that concern us the most are of course the least predictable with the greatest uncertainty so require extreme caution due to uncertainty. You might think Windslab/Stormslab the one that kills the most folk should be "Extra Caution".   But, if you think about it you can work out in advance the Aspects that might be affected from a weather forecast, and very importantly observed wind direction, Angle of slope based on contours, preciptation type and deposition based on Altitude, and what the slope is Anchored to based on summer knowledge of your ski patrol/local area, or previous avalanche forecasts that mention temperature rises and surface or deeper instabilities.
Wet snow release triggering a weakly anchored slope








Think: Angle, Aspect, Altitude, Anchors and Avoid

Powerful wet snow glide avalanche that takes everyting in its path. BEM above Laganbarbh
Persistant slab, skier triggered March 30th 2013 Glencoe



2 comments:

  1. Good read Davy.

    1 = no snow
    2 = off piste is moguls
    3 = off piste is tracked
    4 = off piste is fresh
    5 = lifts are shut

    Obviously not a responsible way to look at things. BUT... for many ski resorts , especially big popular ones in alps it is very close to reality of situation. Something many formal education sources overlook is that skiers are actively looking for fresh snow on 25+ degrees slopes, as its fun skiing. However with fresh snow the risk is almost always going to be level 3 or more. Of course a climber wouldn't go near such a slope on foot if it could be in anyway avoided. But in Scotland we can often only ski where the snow has drifted - which is an added complication.

    Now as a skier I fully accept that lvl 3 = 'considerable'. The problem is that at level 1 or 2 the snow off piste is often not that fun to ski either... (boiler plate scares me too!). Have thought about this a lot over the last 2 weeks and the only conclusion I can come to is that skiers seeking fresh snow (including myself) need to learn to be much smarter about terrain decisions / traps and the consequences of what could potentially happen if something released. The only other option is to stick to piste carving.

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  2. Thanks Doug. I wouldn't give up on the off piste! Back in 2005 Tignes more or less conceded that it's selling of itself as an off piste mecca(SPOT- ski the powder of Tignes)had created the environment that had caused an icrease in avlanche fatalities. They even had/have a dedicated freeride off piste lift served area at the col de Ves and at one time had the first ARVA park, all to mitigate the attrition rate. The chef de piste at that time Jean Louis Touaillon is a great supporter of FIPS and BASP and is now heading up the pistuers at Chatel and for the Sochi winter olympics. The best skiing is when there is some risk, and I for one would not think of stopping doing it. Managing the risk means accepting the uncertainty and replacing it with knowledge, judgement and ways of reducing the consequences. I didn't want to use the gulch as an example, but as a terrain trap it changed any risk assesement as no matter what you or frinds carry or wear the consequence of going in it are huge. This is an example of looking and talking about conditions and running through scenarios of consequences before skiing an area and one that every self respecting guide would intuitively be doing as well as analyticaly doing profiles and other measures to support (or not) their intuition. I dont know that avlx education is anymore than making folk think, look and feel and importantly talk through where and what they are doing.

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