Snow nerds unite

Wednesday, October 17, 2007

By Sam Petri

Jackson Hole, Wyo.-The International Snow Science Workshop is a weeklong program for avalanche professionals. It happens every other year. This being an off year, The American Avalanche Association, in conjunction with the American Avalanche Review, held a Professional Avalanche Development Seminar on October 6th at the National Museum of Wildlife Art. 

It was not intended for the inexperienced, but for those responsible for saving lives: search and rescuers, ski patrollers, guides, and avalanche forecasters.  The all-day event focused on four topics: wet snow avalanches, fracture propagation tests, avalanche survival, and deep slabs.  Of all the esoteric minutia that was discussed regarding avalanches, the most accessible and useful information to laymen came during the discussion about new propagation propensity field tests and then the discussion on avalanche survival: to swim or not to swim. 

Dave Gauthier, PhD, spoke first on a new propagation propensity test he has developed.  Gauthier earned his doctorate from the University of Calgary in Civil Engineering where he studied propagating fractures in weak snow pack layers.  During that time he developed a new field test to measure propagation propensity. 

Gauthier’s test differs from the compression test and shovel shear test most backcountry skiers already know.  The compression test is a common way to test the snow pack on any given slope.  The skier digs a pit in the snow at least one meter deep, isolates a column of snow, then, with his shovel blade on top of the isolated column, taps several times until the column breaks away.  The amount of times you need to tap, how hard you have to tap, and how clean the snow breaks away, lets the backcountry skier know where the snow will fracture as well as how easily it will fracture. 

What the compression test doesn’t show is how or if the fracture will propagate.  
Gauthier’s meathod is to dig a pit one meter long up the hill, and about one meter deep.  Most snow pits are dug across the hill; his is dug up the hill.  He then isolates the column using string and a snow saw.  Once the column is isolated Gauthier then drags the backside of his snow saw up hill through the weak layer in the snow pack.  If the snow collapses and the column slides down hill almost immediately, propagation is high, if he can drag the snow through the weak layer almost the entire way—past the halfway point—propagation is low. 

“We’re choosing the layer we think is going to be the one that has the most propagation propensity or that we might be able to ski cut,” said Gauthier.  In other words, his test is not about finding the weak layer, but understanding what that weak layer is going to do. 

Ron Simenhois, a ski patroller at Copper Mountain Ski Resort in Colorado, and Karl Birkeland, an avalanche scientist with the U.S. Forest Service National Avalanche Center, presented their update on the Extended Column Test, a test they had initially unveiled during the last International Snow Science Workshop in Telluride in 2006.  Like Gauthier’s test, their Extended Column Test is about understanding how the slope will propagate if an avalanche were to occur. 

Simenhois’ and Birkeland’s extended column test is similar to the standard compression test skiers already use, except that the column of snow they isolate is much wider across the slope, at about one meter.  Once the column is isolated, the test begins by placing your shovel on top of the column and off to one side, and tapping as you would on the compression test.  But because the column is extended, during this test you get to see not only where the weak layer is, but also where it will propagate. 

It is an interesting new way to test propagation and find the weak layer simultaneously.  However, their test is still a work-in-progress, as it has given some misleading results in the past. Their write-up on the Extended Column Test will be published in The Avalanche Review December 2007. 

“I think both tests need to be worked with more, by more people, and then we will have a better handle on how well they’re both working,” said Birkeland. “We don’t know yet, but as we collect more data on both of these tests we might find that there are specific conditions where one is favored over the other.”

After a short break it was Dale Atkins, of the Colorado Avalanche Information Center, and Dr. Martin Radwin of Weber County Search and Rescue in Utah, who debated on the topic of “Avalanche survival: To swim or not to swim, that is the question!”
Over many years avalanche books and classes have taught backcountry skiers to “swim” in a backstroke style position—feet first as if in a river—in order to survive if caught in an avalanche.  Despite this conventional wisdom, Atkins took the position of “swimming: the wrong thing to do.”  “I think it’s always good to question authority,” he said.  “Swimming seems like the logical thing to do but the premise it’s based on is wrong.”  Atkins noted that swimming in an avalanche assumes the victim has control.

He also noted that it keeps your hands away from your face and makes it impossible to create an air pocket if buried.  Atkins also noted that the evidence that swimming works is only from those who have survived avalanches - he questioned how many people who have swam have not survived.   Atkins was not claiming that swimming leads to dying, but that the evidence that swimming keeps you alive is biased.  He still believes that you need to fight for your life if caught in an avalanche, but that avalanches don’t act like a river flow - they are a granular flow, and it’s not about floating, it’s about de-mixing.  Particles stratify, and the larger grains rise to the top. 

Stratification is one point Atkins and Radwin could agree upon.  Radwin did agree that “We don’t really know the success of swimming,” but also said that “swimming equals struggling for you life, who could possibly resist?”  Radwin noted that if you are swimming, you are moving your arms and legs, which makes you a larger particle and in a granular flow where larger particles rise to the top: this is a good thing. 

Radwin advocated the Avalanche Balloon System (ABS) that has been in Europe for years but has yet to reach the states for several bureaucratic reasons.  The ABS system comes in a backpack and, when a ripcord is pulled, inflates two large angel wings—though some models inflate around the head instead—that make an avalanched skier a larger particle in the flow.  Research during the past 10 years has shown that using the ABS is the most effective way to survive an avalanche.  Only one person using the ABS has been completely buried and died as a result.  In that incident it was after a secondary avalanche where the victim was swept over a terrain trap. 

“I would love to see a combo device of the ABS balloon pack with the Avalung device,”
said Radwin.  Wouldn’t we all. 

PERMALINK:
Snow nerds unite | Planet JH News Article: Sports & Recreation

Leave a Comment