Deep Instabilities

Posted on Mar 31, 2014

This has been a very interesting winter from a snow and avalanche perspective. The season started off of course with very little snow and some impressively long and cold arctic cold snaps. When the snow finally came it buried a troublesome layer on February 10th that would become a player in the avalanche game over most of British Columbia and indeed on the island as well for some time. Though this layer is no longer a player in the island snow pack, I have been guiding in our back yard here in the Mount Waddington area and I can tell you it has been a player here and continues to be.

This February 10th layer is what we call a persistent snowpack instability. The name is very descriptve in that the layer gets buried under successive subsequent snowstorms which bury it deeper and deeper in the snowpack. The problem with these instabilites is both their depth (because with so much snow on top of the the problem layer you are looking at the possibility of very large avalanches) and it's persistence. As these things persist in the snow pack and get more and more load on them, our problem as forecasters is knowing when and where the critical load will make this layer fail. The fact of the matter is that we are not very good at making those predictions with these kinds of instabilities. Indeed these deep and persistent avalanche problems are the ones that we are least good at predicting.

I think that the management of these deep and persistent avalanche problems makes a great metaphor for a range of risk management decisions which we make in the mountains or anywhere in life for that matter. The fact that we are not good at predicting this problem should dictate what "risk treatment" we give it. An important first step I think is that we have to recognize that we have low confidence in our ability to predict. In the case of the persistent slab avalanche problem, given this lack of confidence in our ability to predict when or where these things will happen, we are left really with one option to manage the risk: conservative terrain selection. What this has meant for us at times this winter is not only skiing on low angle terrain that is not avalanche terrain, but also being vigilant about not having avalanche terrain above us either.

I think that we can take some lessons from the management of this problem into other areas of risk management in the mountains and elsewhere. In any hazard assessment I think it makes sense to try to objectively measure your level of confidence in your assessment. Ask youself how sure are you of the likely hood of realizing the hazard as well as the magnitude of the outcome should you realize it. If your confidence in these predictions is high because you have a lot of really good information and the information at hand relates directly to many experiences that you have had, then you can justifiably have high confidence in your assessment. But if you lack good information and/or what you are seeing does not relate directly or even indirectly to experiences that you have had or if you have not had much experience, then perhaps you should assign a lower confidence to your assessment and choose a more conservative decision around that hazard.

I guess in simple terms what this amounts to is being honest with yourself about how much you really know about a risk that you are trying to assess. If you are not so sure, then rather than flirting with a coin toss maybe the better chocie is to say no and pursue another option. Or even more simply put: If in doubt, don't.

I want readers to know that after 30 years in the avalanche game I am more happy than ever to talk about my lack of confidence and what I don't know. Indeed I think that being able to identify what we don't know and acting accordingly could be one of the most important skills in risk management.

Have a great spring out there and play safe!