Snowmobiles and Avalanches
It’s not often that one single piece of information can save your life. Most of the time, especially in the backcountry, it takes years of training and experience to evaluate conditions, your ability and the technique necessary to take on a route, whether that be ice climbing, backcountry skiing, rock climbing or snowmobiling.
In the case of most snowmobile related avalanche accidents, one piece of information can prevent about 50% of deaths and injuries.
Snowmobiles usually trigger accidents when highmarking. The last decade has seen a revolution in the power-to-weight ratio of snowmobiles, and the popularity of the sport, so more people are heading for the hills. The machines can get to more terrain faster, and they do get everywhere.
While highmarking, one rider will gun the machine up a slope, usually while others watch. On the face of it this seems to be a good idea; the observers can keep track of the rider’s progress and go to help him if he gets in trouble. Unfortunately this impulse, to observe and to help, is what causes at least half of the deaths.
There are two general scenarios for snowmobile-related accidents.
The first is when the highmarker triggers an avalanche which sweeps down the slope and buries the observers. Being relatively uninformed, the observers usually choose to watch from the potential runout zone of any avalanche that is triggered by the highmarker. Incidents of this sort are the cause of accidents such as the the recent deaths of three snowmobilers at Mount Gerald near Golden, BC. In this accident one rider was clearly highmarking, while the others were waiting in the runout zone.
The second scenario happens when a highmarker gets into trouble and his or her friends go to help them. Again, this is seems to be a reasonable response, and again it results in fatalities when the weight of the second machine in close proximity to the first triggers an avalanche and both riders are buried. An example of an accident of this type is a fatal accident at Queest Mountain near Sicamous in 2010. In this accident, the deceased person had been attempting to help a friend when the avalanche happened. The friend broke both legs and survived.
A final example comes from the accident at Boulder Mountain near Revelstoke, BC from last year. Several hundred people were at a backcountry snowmobile event when two sleds climbing a hill triggered an avalanche. Two people died, seven were badly injured and 32 injured otherwise when the slide hit them while standing in the runout zone. By all accounts, and by inspection of the number of damaged sleds in the avalanche debris, at least 30 and perhaps as much as 70 people were directly in the path of the avalanche.
Video of previous a previous event where no accident occurred:
The simple solution to prevent about half of the snowmobile related avalanche deaths is for sledders to stay out of the runout zone.
Basically, taking a page from the backcountry skier’s playbook, only one person should be exposed to a hazard at any given time. When skiers ski a slope one at a time they stop at what’s called islands of safety. An island of safety is an area where an an avalanche is unlikely to be triggered, and outside of an obvious avalanche path. This can be something as simple as the side of an avalanche path, a small rise, or a ridge crest. The trick is in choosing these so that you can still observe the other skiers travelling a slope. Knowing where the island of safety is can also help while skiing because it gives you a target to make for in case an avalanche happens and you need to get out of it’s way.
Staying out of the runout zone means not stopping at the base of the hill in the obvious place where an avalanche will bury you. It also means that if a sledder gets into trouble on a slope, do not send someone out to help. This is bad because your action can in fact kill the person you want to help, along with yourself.
The higher the danger, the greater the precautions. One at a time is always a good idea, and so is staying well beyond the maximum extent of the slide. If it’s not possible for some reason to get out of the path, then point the snowmobile away from the slide, and leave the engine running. This gives you the best chance of escaping or outrunning an avalanche.
Of course, this is easier said than done. Many sledders, when interviewed after an incident seem to say things like “that never happened in 32 years of sledding here.” It seems there is some problem with identifying the hazard in the first place, and recognizing that they are in the path of a potential avalanche. They also seem to have trouble acknowledging that simply sledding for 10 or 20 years and not having an accident does not means you are “experienced” – luck in this case does not mean knowledge.
As I mentioned in a previous post on avalanche danger, the moderate to considerable rating is one of the hardest to manage. Considerable is often used to describe a situation when there is a persistent weak layer in the snowpack – resulting in conditions where avalanches are possible is specific conditions, and in certain areas. This is particularly problematic with snowmobiles because of their weight. The force of a snowmobile on the snowpack is much greater than a skier hiker or boarder. Where the weight of a person may not be enough to trigger the buried weak layer, the weight and force of a snowmobile might.
Tips for sledders to manage avalanche risk
- highmark one at a time
- travel through dangerous terrain one at a time
- do not stop in the avalanche path or runout zone
- stop with machines facing away from the slide
- leave the engine running
- do not assist stuck sleds if at all possible (i.e.: unless there is an injury)
Avalanche Accidents in Canada, Volume 5, 1996-2007, Jamieson, B,; Haegeli, P.; Gauthier, D. , p.429, (2010)