March 16, 2012 | Back to: News

Avalanches: Education key in avoiding dangerous, unstable slopes

TAHOE/TRUCKEE — A confluence of factors has led to a winter season prone to avalanches in the backcountry of the Lake Tahoe-area alpine environment, officials said.

A shallow snowpack causing persistent weak layers combined with winter recreationists' zeal for powder adventures make for a dangerous mix, said outdoor officials.

“When a whole bunch of heavy snow falls on top of (a weak snowpack), it's basically like putting a brick on a layer of potato chips,” said Andy Anderson, an avalanche forecaster with Tahoe National Forest.

Obviously, that brick will break the potato chips, causing a series of naturally occurring avalanches, Anderson said; however, in certain instances the heavy snow drives the weak layer right to the edge of fracture, where all it needs is one trigger.

And those are instances of extreme and potentially lethal danger, Anderson said.

However, Anderson does not want to discourage adventurers from entering the backcountry, but rather those who do venture outside the boundaries of the ski resorts should be familiar with avalanche terrain.

“Avalanches are completely predictable,” he said. “It is up to the individual as to how to engage the hazard — but there is a wealth of evidence that points to an unstable slope.”

Three factors must be present for an avalanche to occur: a steep slope angle, a weak layer in the snowpack and a heavy slab on top.

Due to the presence of two out of those three factors, recreationists should avoid steep slopes in the backcountry for the foreseeable future, Anderson said.

Also, avalanches are not unique to skiers and snowboarders, as anyone pursuing an outdoor winter activity — such as alpine climbing, snowmobiling, snowshoeing, ice climbing or hiking — are susceptible to the devastating event.

The best prevention is education, and those interested in undertaking backcountry adventures are advised to take classes on avalanche recognition, Anderson said.

Alpine Skills International (www.alpineskills.com) and the Sierra Avalanche Center (www.sierraavalanchecenter.org) both offer a variety of avalanche classes, depending on the ability level of the student.

“Backcountry skiing is popular and growing fast,” said Brendan Madigan, manager of Tahoe City-based Alpenglow Sports.

Last year, the Tahoe Daily Tribune and Sierra Sun reported on the increase in popularity of “earning your turns,” or backcountry adventures for skiers and snowboarders.

For many of the officials and practitioners interviewed, the lure of the backcountry was largely predicated on the ability to experience the calm and solitude of nature in the winter without the frenetic experience of crowded runs and packed lift lines.

Improvements in technology — including split-boards and Alpine Touring bindings — make the experience available to those of different skill levels and more affordable for everyone.

Jason Auld, owner of Mountain Recreation in Grass Valley, said his store is beginning to carry more backcountry tools to accommodate a rising demand.

Auld said he has also seen an increase in those opting for a sidecountry experience, which entails riding a ski lift to the peak of a mountain, but finding lines outside the boundaries of the ski resort.

Avalanches are deadly, Anderson said.

“Imagine being caught in the spin cycle of a washing machine and having that tumble down a mountain slope at high speeds,” Anderson said.

About 30 percent to 50 percent of avalanche deaths result from trauma suffered in the initial fall, Anderson said. If people are lucky to survive the initial tumble, many die due to suffocation after being buried beneath snow.

As snow falls down a gradient, the friction created warms the temperature of the snow. Once it comes to a rest, cold temperatures quickly refreeze the snow, making movement underneath impossible.

“You certainly can't dig yourself out,” Anderson said. “Even if the layer on top is only a foot.”

Once trapped, a person exhaling creates an impermeable ice chamber immediately in front of the nose and mouth, meaning a person has about 15 minutes worth of air.

Those extricated from the snow within the first 15 minutes have about a 90 percent survival rate. Between 15 and 30 minutes, the rate dips just below 50 percent, and after a 30-minute period, the survival rate is below 30 percent.

Recent developments such as the ABS Airbag, a device manufactured in Europe designed to keep a person caught in an avalanche near enough to the surface to prevent burial, may mitigate the lethal danger, but not eradicate it.

Such products are selling well, Madigan said.

The current season in Tahoe, and around the country, has been unusually avalanche-heavy, according to multiple published reports.

Benjamin Bracket, 29, of Olympic Valley, died March 1 after a slide near Ward Canyon off Tahoe's West Shore.

Nevada City native Megan Michelson was involved in a harrowing avalanche experience in Washington, where she attempted to extricate three close friends who had been buried in a large avalanche to no avail.

The Lake Tahoe region has long been favored by backcountry explorers due to the stability of the snowpack, particularly relative to other North American alpine environments.

However, due to strange weather patterns, the current winter season features a more precarious backcountry experience.

“In the Sierra sometimes we can get lulled into a sense of safety because of a stable snowpack,” Madigan said, adding that minimal snow and colder temperatures have combined to offer a snowpack similar to that of the Rocky Mountain region.

— The Union is the Sun's sister paper in Grass Valley and Nevada City. The Union's Brett Bentley and Tahoe Daily Tribune's Adam Jensen contributed to this report.

Matthew Renda
The Union


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Tahoe Daily Tribune Updated Mar 16, 2012 02:10PM Published Mar 16, 2012 02:04PM Copyright 2012 Tahoe Daily Tribune. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.