Avalanche Safety for Backcountry Travelers

An excellent and timely article. Thanks Kevin.

To the best of my knowlegde, there has been just one avalanche in the Australian snow fields over the last 20 – 40 years. I have no idea why, and I suspect >99% of our ski tourers never even think about avalanches.

So interesting stuff, but not something we see in Oz. Weird.

Cheers
Roger

I strongly suggest that anyone really interested in safe winter travel disregard this article and instead first read either the book by Bruce Tremper that I assign to my avalanche course students:
http://www.mountaineersbooks.org/Staying-Alive-in-Avalanche-Terrain-2nd-Ed-P512.aspx
… or his new book that is on a more introductory level:
http://www.mountaineersbooks.org/Avalanche-Essentials-P1170.aspx

If you do read this article, then here are some corrections for some of the most egregious aspects:

1. I count seven references each to beacons and probes, yet not a single reference to shovels. Maybe the implicit assumption is that each and every winter traveler will already have a shovel, but still, this has to be some kind of first for an article about avalanche safety to omit any reference to shovels.

2. “Let’s dispel a few myths. […] Second, most avalanches do not kill by burying their victims. They are more likely to kill by sending an unsuspecting skier over a cliff or by smashing them into rocks or trees.”
– Exactly the other way around, i.e., the usual statistic is about 3/4 asphyxiation (via airway burial) versus 1/4 trauma. (Avalanche deaths for technical climbers can be more like around 1/3 trauma, but the only study I’ve ever seen for a majority of avalanche deaths via trauma is my own analysis of deaths on NH’s Mt Washington.)

3. “Slopes with angles between 25 and 40 degrees of steepness are the most prone to avalanches.”
This statement is very misleading, and the accompany diagram from some book is even worse, both for its portrayal of slopes between 40-45 degrees, and the misuse of the word “Moderate” in this context, since it is one of the descriptors on the five-point avalanche forecasting scale.
The statement is contradicted even by the accompanying diagram, as well as by the typical classification, as found in the older Tremper book:
“Slopes between 35 and 45 degrees cause the vast majority of avalanche fatalities […]. Recent statistics from Canada and Switzerland indicate that half of human-triggered avalanches occur between 37 and 42 degrees […].”
… by his newer more introductory book:
“In the steepness graph […], the bull’s-eye steepness is 39 degrees; nearly three out of four avalanches occur in red-light starting zones (34 to 45 degrees), 10% occur in the yellow-light terrain on the gentle side of the curve (30-34 degrees), 13% on the steep end of the curve, and only 3% on slopes less than 30 degrees.”

4. “If you take an avalanche course you’ll be taught about digging a snow pit to assess for unstable layers.”
Teaching snowpit assessment skills is no longer part of the standard Level 1 three-day curriculum.

5. “In the Sierra we get a very heavy “marine” snowfall […]”
Tahoe does have a maritime avalanche climate, but not the Eastern Sierra.

6. I’m not going to get into the snow science aspects of the article except to note that depth hoar often seems to be confused here with buried surface hoar.

Kevin,

Excellent article with great illustrations. As an avy certified ski patroller in an avalanche prone area (Las Vegas Ski & Snowboard Resort in Lee Canyon, Spring Mountains) I applaud this timely article as not only intertesting but necessary for those travelling in avy territory.

MINIMUM AVALANCHE SAFETY KIT:

1. Avalanche One course
2. avy beacon
3. probe
4. avy shovel (no plastic blades)
5. snow study kit (inclinometer, compass, magnifier, thermometer, etc.)

RECOMMENDED AVY GEAR:

1. snow saw (for Rutschblock and snow pit study)
2. Avalung
3. avy air bag backpack (BCA pack, for ex.)

Then go out with other similarly equipped friends and PRACTICE.
Practice finding a hidden beacon.
Practice team digging for buried beacon using > shaped digging technique and "paddling" movement of snow.

IN AVY TERRAIN:
Practice maximum caution for route selection. Testosterone-charged macho attitudes lead to abandoning proper caution. This is why groups that include females have a much lower chance of being avalanched. (true)

Again Kevin, thanks for a great article. This article, with any needed updates, should be posted EVERY year at this time.

UPDATE: Worldwide statistics show that those avalanched with DEPLOYED airbags have a 90+% chance of survival. Most of the data comes from Europe and North America. The European avy areas are much less forested than in North America. Therefore the statistics are somewhat skewed by the European data. Still, even with an 80% chance of survival an airbag pack should be virtually mandatory for any commercial heli-ski operations and "highly recommended" for backcountry skiers.

Every avalanche course is different, and they are different across different parts of the country due to huge differences in the makeup of snow.

Sometimes a whole snow study kit is demonstrated in a first-level class, but often it isn't used until a second-level class.

A few of us managed to study the snow very quickly on our first unexpected ride down the hill. For my second event, I had the opportunity to study the snow from the underneath.

–B.G.–

When I took my level one course ~5 years ago snow pits and avalanche study kits were covered. Given how differently snow can behave short distances apart I usually dig only 1-2 snow pits per trip just to get a sense of what is happening deeper but I rely on the general information and terrain aspects most.

Billy:

Same reason I'm always willing to loan my triple antenna beacon to a newbie with a lesser device! If it's needed you want the person looking for you to have the best.

Every avalanche course is different, and they are different across different parts of the country due to huge differences in the makeup of snow.

Indeed, and in different countries too. Here in Scotland windslab avalanches are the most common, so it is important to know the recent wind and temperature history when going out.
The classic text for Scottish conditions is A Chance in a Million?

What some cross country ski groups do is to have a transceiver practice in sloping sand dunes. Basically, one transceiver is left in the transmit mode, and then placed in a plastic bag, and then buried in a sand dune. Then the sand is smoothed over. The trainees arrive, switch over to receive mode, and then look for the target.

It doesn't take too much practice to get the hang of it.

–B.G.–

Kevin, Excellent article. This is obviously geared toward beginners, and the concepts you illustrated provide a very good stepping stone to more advanced education.

One MAJOR concept that should be included when discussing avalanche terrain is slope convexity vs. concavity. Convex slopes, even if the they start at shallow angles, are exceptionally weak, and can act as dangerous trigger point for much larger avalanches. More info here: http://www.fsavalanche.org/encyclopedia/convex_slope.htm

>To the best of my knowledge, there has been just one avalanche in the Australian snow fields over the last 20 – 40 years.

I think small slab slides are not that uncommon.
The Aussie ski forums have several reports of near misses.

I definitely agree that Aussie ski tourers are worried much less about them than those in the states.

http://forums.ski.com.au/xf/threads/avalanche-rescue-on-bogong.22624/
http://forums.ski.com.au/xf/threads/avalanche-risk-australian-backcountry.49574/