Friday, January 29, 2010

A Sobering Week


So Wednesday presents a difficult day in the Wasatch when you remember the frailty of human life and the consequences of your life decisions. Let there be no doubt, Back Country Skiing is dangerous and should be taken very, very seriously. For those of you that read this and other such blogs, I'm sure you will hear this re-sound throughout the community.

This Wednesday Ricardo Presnell - 51 was enjoying a beautiful day of skiing in the Solitude back country in the meadow chutes. Ricardo was caught and carried by a large hard-slab slide that ran almost full track through rocks, shrubs, and aspens on a Easterly aspect, convex glade ranging from 35-39 degrees as measured by the Utah Avalanche Forecasters. From Bruce Tremper's photo's taken across the canyon the slope looks very benign, even low angle.

That same day one of my ski partners and I where ascending the ridge between Willow and USA bowl and I specifically remember looking over to the meadows and commenting "Why haven't we been skiing their yet?" As always we where speaking in sarcasm because the meadows in a great place to ski based on effecient use of your time. Its a short hike with good skiing in lower angle terrain that has a selection of meadows and tree runs with excellent access. This year we tend to be following the theory of 'skin a lot, ski a little.' So of course the meadows wouldn't be on our list. At this point I don't think the slide had happened yet and shortly after the clouds rolled in and we no longer had a view of much except what we where on. We continued to ski the day without incident skiing primarily West and South West aspects ranging mostly in less than 35 degree angles. On the way in we observed a steeper wind loaded South South West section on the ridge that had slid as you can see from the photo.

Its really pretty amazing the lack of stabilization in the snow pack after waiting so long from the last storm. During a normal season it would be unheard of to have a considerable rating and be worried about drastic hard slabs 4 -5 days after a storm. The Wasatch has a unique blend of dryness, moister, and moderate temperatures that help our snow pack consolidate at a rapid rate yet they don't tend to rot as rapidly as you would see with a colder, or more continental snowpack. The issue this year is not a change in temperature, but a change in rate of snow accumulation. Anytime you get snow fall rates approaching 1 inch per hour or greater the red flags should start coming out, not only that when you increase the total snowpack depth at a large rate, say more than a 10% total increase, all of the sudden things get really dicey, dicey not just in the new snow, but the ability of the old snow (or the hard slab) to support the new weight. Think of it like a rubber band: As you add snow you stretch the rubber band, the faster you add snow the quicker you stretch it, an as the % of the previous total increases, the rubber band stretches also. So we reached a point where the snow pack depth had increased OVER 300% in 48 hours (not even counting the wind loading). and you have a rubber band that is completely spent. You can see evidence of it snapping ALL over in the big, dangerous paths like the west ridge of desolation and Murdock basin that the entire season snow pack came out at once in a deadly, and very destructive slide. At least on of them was triggered from the flat (yes, that is correct) ridge line above. A few things to always keep in your mind with the hard slabs is

1.)if they break the conciquences are really bad.
2.)they can break above you (this is why you don't ski cut a hard slab)
3.) They can be triggered from a higher angle secion (say 35 degrees or higher) and pull out snow on much, much lower angles, even flat surfaces that have bonded with the slab.
4.) Also with hard slabs its not always the first person who triggers the slide, So a slope with tracks can still break loose. Think of the Canyon's ski resort accident recently that broke after dozens of descents and a long history of skier compaction. If you look at the meadow's slide you can see that most of the lines had been skied multiple times already for a day or two. I wouldn't doubt that Ricardo's slope had been skied before.

If you recall a few years back to little water peak, a slide was triggered on a roll over that just broke the 35 degree mark yet pulled the lower angle snow around it with it in the 32-34 zone.

As always, since the snow tapered off, the snow has slowly been stabilizing, unfortunately its happening very, very slowly. Much slower than we are used too. It's always good to take a step back and think about your mortality during these times and re-evaluate your decision making. I like to go back to Bruce's analytical view. (Staying alive in avalanche terrain, Bruce Tremper pg 20)
Constants:
1. You travel in avalnahce terrain 100 days per year.
2. You cross 10 avalancehe slopes per day.
3. The snow is stable enough to cross on 95 % of the slopes
4. For every avalanceh you accidentally trigger, you get caught every third time and kille d every tenth time.
Based on those constants if you made good choices 99% of the time then your life expectancy in the mountains would be 2 months. Yes, thats what he said, 2 months. So I would like to turn down the constants and change the travel days to a more reasonable number of 50 days of skiing/traveling in the back country per year. So with that change it would equate to 4 months life expectancy. If your a weekend worrier, and say you only get out 25 times per year, then that brings your life expectancy up to 8 months. Still, one ski season. So you get the point, your odd's of dying with the above constants, making 99% good decisions, are that you will die in the first season of back country skiing... I'll say that again --If you make the right choice 99% of the time in the back country, odds are you will die in the first year.--

Now this doesn't account for proper recover with a beacon, an avalung, or baloon pack. All of these things will increase your risk of survival if used properly. That being said, somewhere in the neighborhood of 30% of those caught in an avalanche are killed by trauma, and in this case, a beacon recovery or an avalung, or a ballon pack wont help you. The goal then is to not get caught in a slide, ever. On the positive side, if your decision making is correct 99.99% of the time, then you have an estimated life expectancy of 100 years, skiing 100 days a year, 200 years skiing 50 days a year, and finally 400 years skiing 25 days a year. That sounds a little better.

In conclusion, know how to read the terrain, the snow, be skilled with your beacon, spend the 200 on the Avalung, dig pits, do rutschblock tests, dig handpits, read the avalanche forcast, and listen to what people are saying, especially your peers. If someone is nervous, then listen. If your not comfortable with your assesment skills then wait for the rose to turn green, or ski at the resort.

Please check out the full accident report at:
http://utahavalanchecenter.org/accident_meadows_1272010
and more photos at: http://avalanche.org/~uac/photos/Images09-10/Meadow_Chutes/

Recommended reading: http://www.amazon.com/Staying-Alive-Avalanche-Terrain-Tremper/dp/1594850844/ref=tmm_pap_title_0

2 comments:

  1. thanks man, I love reading these blogs.
    Preston

    ReplyDelete
  2. You bet. I'm glad you enjoy it.

    ReplyDelete