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Human causes of avalanches

post #1 of 9
Thread Starter 
Hey, all -

Don't know if you've seen this, but my ski group has been discussing this paper today and it's worth reading by anybody who ventures into the backcountry.

It's a study called "Evidence of Heuristic Traps in Recreational Avalanche Accidents" by Ian McCammon of NOLS, presented at the International Snow Sciences Workshop in 2002. Most of us are aware of this info but it's a good reminder.

My ski partner and I had an incident last week... he triggered an avalanche and unfortunately was swept down. The slide was pretty good sized and strong enough to take out a couple of small trees, but he was OK.

We made the mistakes outlined in this paper. Learn from our mistakes.

Anyway, here is a link to the paper.

Here is the abstract:

Quote:
Even though people are capable of making decisions in a thorough and methodical way, it appears that most of the time they don’t. A growing body of research suggests that people unconsciously use simple rules of thumb, or heuristics, to navigate the routine complexities of modern life. In this paper, I examine evidence that four of these heuristics – familiarity, social proof, commitment and scarcity – have influenced the decisions of avalanche victims. Using a quantitative method to define the level of hazard exposure in 598 avalanche accidents in the United States, I compare the behavior of the victims when heuristic cues were present to their behavior when these cues were absent. Key findings of this study include: 1) evidence that social proof, commitment, and scarcity traps were significant in many accidents, 2) evidence that group size influenced susceptibility to certain heuristic traps, and 3) evidence that the level of avalanche training in victims influenced their susceptibility to heuristic traps. These findings strongly support the idea that tools for managing heuristic traps are essential for effective avalanche education.


post #2 of 9
This is a great article and was reprinted nearly in its entirety in 2 issues of Couloir magazine this past fall. It is also on www.snowpit.com.

Glad to hear that both of you are OK- be careful!
post #3 of 9
Thread Starter 
Quote:
Originally Posted by dp
This is a great article and was reprinted nearly in its entirety in 2 issues of Couloir magazine this past fall. It is also on www.snowpit.com.

Glad to hear that both of you are OK- be careful!
Thanks, David, it got our attention, that's for sure...
post #4 of 9
Let's all rope up together and see if we can kick our way across this open bowl. If we stay just under the cornice, we won't need to expose ourselves to that howling wind. Look at that group just below us, I be they wish they had our view!

CalG
post #5 of 9
The article is a valuable for analyzing group and individual decision dynamics, and is touched on in a lot of the referenced cited for the article. Thanks for posting the link. Personally, I still find it easy to get sucked into the "if its tracked its safe" (social proof) and "its a powder day" (scarcity) huristics. Being aware can at least let you trigger alarm bells when you see it happening, and take a moment for additional assessments or tests.

It sounds like you had a fairly scary experience, and I'm glad that you and your partner came out of it OK. Would you be willing to post the details of your trip, and analyze your decisions, right and wrong, and the causes /lessons learned from your experience? I know that its often diffiicult to revisit decisionmaking errors, but sharing them allows a much broader community to benefit from your experience, possibly avoiding the same mistake. Posting a link to the article is appreciated, but learning from your experience would be more valuable. In the context of the decision heuristics article, what happened on your outing?
post #6 of 9
Thread Starter 
Quote:
Originally Posted by Cirquerider
It sounds like you had a fairly scary experience, and I'm glad that you and your partner came out of it OK. Would you be willing to post the details of your trip, and analyze your decisions, right and wrong, and the causes /lessons learned from your experience? I know that its often diffiicult to revisit decisionmaking errors, but sharing them allows a much broader community to benefit from your experience, possibly avoiding the same mistake. Posting a link to the article is appreciated, but learning from your experience would be more valuable. In the context of the decision heuristics article, what happened on your outing?
I don't mind sharing, but the names will be omitted to protect the innocent...

We had a fairly significant wind event the previous Friday, which scoured the mountain down to the ice and which created a tremendous slide surface. Saturday's ski experience was brutal - I was able to find soft snow but it was a hunt. We got more snow Monday/Tuesday and Wednesday evening. I skied a long (3000') low-angle face Wednesday morning and was quite happy with how it went.

Thursday I met my partner in the morning and we sledded up to a cliff band where we ski quite regularly. There was a lot of new snow on the ground (about 1.5' from Wednesday's storm on top of another foot or so from Monday and Tuesday), and given the previous week's weather conditions we were concerned about slide danger. This particular cliff band is protected and north facing, and was not subject to the scouring the rest of the mountain received. Another ski friend told us it skied well on Saturday - between all of us somebody is generally skiing this part of the mountain once or twice a week. We know that the chutes in the band are subject to sliding and we generally stay out of them unless conditions are bombproof. We do try and pre-release one of them (the chute in question) just to keep it from building up too badly.

Anyway, because we're so familiar with this area we didn't dig a pit. We skinned up to an area skiers' right of the cliff band that is somewhat lower angle than the chute (33% or so) and treed. Skied down one at a time, no movement, exceptional skiing. We were pretty stoked that we didn't even get a sluff. We skinned back up and my partner wanted to try the chute - about 38-degrees, squeezes down to about 6' wide at the narrowest point. He is significantly more experienced than am I and has quite a bit better avy training... anyway, I trusted his judgement. He jumped in first, didn't pre-release the snow, about the third turn in at the exit of the chute the whole thing released. Crown was about 2' deep, 100' wide, and it ran about 400'. I watched him go down... he wasn't buried but was briefly headed towards some small trees. Fortunately he avoided them, but the slide took out a couple of them. He was fine but we were both shaken up.

We talked about it afterwards, because we both ski alone quite regularly. What would we have done if we were up there by ourselves? We agreed that neither of us would have skied the chute... we would have stuck to the lower-angled run skiers' right. Having the company along gave us a sense of security that contributed to our mishap.

So - did we make every single mistake in the book? Yep. Let me count the ways:

1. We ski this area very regularly and even though we take basic precautions we never dig a pit. (We knew slide conditions were ripe, though, it didn't take a pit to tell us that).

2. We know that this chute is subject to sliding (hell, we call it "Sure Thinig") and skied it anyway, even with the conditions we had.

3. We didn't pre-release the chute, we didn't cut the slope below, we didn't take any of the precautions that could have been taken.

4. We pushed it beyond what we would normally do because we each had a partner we trusted.

5. I trusted somebody else's judgement rather than trusting my own.

We did do a few things right:

1. We both had beacons/shovels/probes and knew how to use them. Had it been necessary to find him I would have at least known how to use the tools efficiently.

2. We skied it one at a time, watched each other down. When he went down I was able to keep a good eye on where he was.

3. We both have emergency medical training and first aid/emergency kits - had there been a need we would have had the knowledge and equipment to help ourselves.


That's it, it ain't pretty and I'm not proud. To be honest it's damned embarassing to have made stupid mistakes like that, because he and I both know much better. However, I guess we all need a wakeup call sometimes, and I got mine last week. At least we're both alive to be embarassed.

Hopefully, rather than look at this and scope out all of the things my partner and I did wrong, you'll examine your own experiences and question how many of the rules we all break because "it'll never happen to me." It can, it does and it eventually will.
post #7 of 9
Thanks, Sue- I think that we can all learn a lot from these reports.
post #8 of 9
Good report Sue, I think it would be outstanding if there was more sharing of information like this. That was a pretty good size crown and a scary ride. I'm glad it worked out well. You won't get criticism from me, I'm still a student here. Could be a while waiting for that. Did you figure out what the weak layer was?
post #9 of 9
Not armchair quarterbacking btu when skiing chutes i like to find cornices and cut them to "bomb" the slope. Its not foolproof by any means but its a pretty good load on the slope.

I have to admit i might very well have skied that chute too.

One thing that i've become much more aware about since getting significant time in the Rockies and Selkirk is the effect of wind. Its amazing what wind loading and wind slab can do.

thanks so much for the report
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