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Multiple Burials: Staying out of the Headlines

Are multiple fatalities in avalanche accidents becoming more common? And should this influence your decision when you’re buying snow safety equipment? Let’s look at the statistics, the gear, and the realities around multiple burials.

“Five killed in Loveland Pass avalanche.” “Three die in out-of-bounds snowslide near Stevens Pass.” “Seven perish in guided trip near Revelstoke, BC.”

Attention-grabbing headlines like these can lead people to think that multiple fatalities are happening at a higher rate. However, statistics indicate that multiple burials have actually decreased over the past decade. And they also indicate that you’re much better off using your brain than relying exclusively on your equipment—especially when more than one person is buried. The best things to do are to get educated, learn proven search techniques, and practice them several times every season.

“Marking” is Born

bcatracker3Multiple-burial talk has its genesis in the guiding world where, for economic reasons, large groups often ski together—and occasionally get buried together. If an accident occurs, the rescue expert in the group (usually the guide) is expected to find all the victims while guests act as assistants or bystanders. To become a certified guide, a candidate is usually required to find at least three victims (one more than two meters deep and two in close proximity) in a short period of time, with minimal assistance. In more realistic guiding exams, the candidate is required to find only some of the victims, but must dig them out within the time limit, usually well under ten minutes. From this world, “marking” functions on avalanche beacons were born.  Marking enables the searcher to suppress the signal of the found victim, then move on to the next victim while others begin shoveling.

Multiple Burial Stats

How does this apply to recreational backcountry riders and how well does it all work?

Statistics show that as recreational backcountry use has increased relative to guided backcountry use, and as equipment and education have become more widespread, the proportion of multiple burials has decreased over time. Currently in the US, Canada, and Europe, about 15 percent of accidents involve multiple burials.  A recent study by the Swiss Avalanche Institute concluded that burials involving more than two people have gone from 10 percent before 2000 to less than 5 percent since 2000. And only about 1 percent of accidents involve close-proximity burials, in which the victims are buried within 10 meters of each other (these papers can be found here). Only in close-proximity situations are most multiple burials solved any differently than a single burial.

In most cases involving two or more burials, the victims are located the same way as single burials, either “in series” or “in parallel.” In the former, a single rescuer locates the first victim, digs enough to provide that victim an airway, preferably turns off that victim’s beacon, then moves on to the next victim (in series). In the latter, two or more searchers fan out across the debris pile (in parallel) and isolate signals as they go.

The only exception is when the victims are close together, within about ten meters of each other. In this case, it’s possible to skip right over one victim’s signal by charging off in the wrong direction. Or in the “parallel” multiple-searcher scenario above, one searcher might end up isolating two signals, but the other searchers might not isolate any. In rare “close proximity” burials like this, special techniques or technologies can come in handy.

Special Techniques

Proven techniques used to solve these situations include “micro search strips”—popular in Canada—and the European-inspired “three circle method.” We won’t get into details (you can learn these in an advanced rescue course), but they’re based on using signal strength to isolate each victim. Generally, the searcher begins at the victim’s last seen point and systematically travels through the debris, making sure he or she doesn’t miss any areas. All modern avalanche beacons are programmed to bring you to the strongest signal, although some do this a lot better than others. As long as you keep moving—and stick to a disciplined search pattern—you’ll find all of the buried victims. Keep in mind that, if you can’t turn off the found victim’s beacon, you’ll have to ignore that signal as you move away from it.

Special Technologies

The above might seem like a lot of excess running around, especially when lives are at stake and the clock is ticking. Enter “marking,” also known as “flagging” or “signal suppression.” Most digital avalanche beacons now offer a feature that enables the rescuer to press a button that suppresses the signal of a victim that has been found, then immediately see the signal of the next-closest victim and move directly to that location.

This technology can work great, especially with only two victims. But once there are more than two, it gets increasingly unreliable. A 2011 report in the professional journal, The Avalanche Review, concluded that marking functions fail up to 70 percent of the time in scenarios involving three and four victims. And once it fails, then you’re worse off than if you simply used one of the proven signal-strength techniques above. That’s because when using marking, the user abandons the disciplined search pattern that’s required to ensure all victims are found. Once you get off that pattern, all bets are off on a thorough search.

What causes this failure? A phenomenon called “signal overlap.” This is when the “beep” from one victim’s beacon occurs at the same time as another victim’s “beep.” When this happens, the searcher’s transceiver no longer knows how many signals are present. If the rescuer “marks” a victim, then both signals could be eliminated—whether or not both victims have been located. Also, when signals overlap like this, a signal that has been marked can all of a sudden become unmarked. The only way to salvage your search at this point is to “reboot” your beacon (turn it off and on again), go to analog mode with some models, or go to the “scan” function on others. But if you don’t know you should do this—or aren’t very good at it—then your search can quickly turn into a train wreck.

Realities

As you can see, avalanche transceivers are not foolproof in multiple burials—even the most expensive and sophisticated ones. Remember the following:

  • The biggest challenge in most avalanche rescues is digging. This takes far more time than the beacon search. In most recreational avalanche incidents there are barely enough shovelers to excavate a single victim, let alone two or more. Are you really going to NOT dig somebody up? For these reasons, in almost all multiple burial scenarios, “marking” is a luxury. People will die if you don’t start shoveling—immediately.
  • In most guiding exams involving three or more victims, guides generally do not use marking: they use proven signal-strength search techniques such as micro search strips. This is because there’s a good chance marking will fail.
  • It’s more important to master 1- and 2-victim scenarios and “strategic shoveling” than it is to focus on complex, special-case multiple burials. When practicing multiple burials, try marking first. If that doesn’t work, use micro search strips. Click here to learn more about these proven techniques.
  • Better yet, prevent multiple burials from happening. You can do this through smart route planning, safe travel techniques (one at a time), and effective group communication: lots of discussion, open sharing of ideas, and the efficient use of two-way radios.

The good news is that even though they attract lots of attention, complex special-case multiple burials are about as likely to strike as a millennial slide path. Get educated, practice the basics, stick to good travel protocols, and you’ll stay out of the headlines.

To find a training center near you and other avalanche resources, visit avalanche.org or checkout the AIARE’s course list.

For more info and training videos, visit www.backcountryaccess.com/education.

Related

How a Beacon Search Works
Out of Bounds, Sidecountry, Slackcountry: It’s All Backcountry
How to Read Avalanche Terrain When Route-Finding

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1Comments

Here's what the community has to say.

George Reid

George Reid

Great article Bruce, very well written, easy to understand.



It is all too easy for folks to get swayed by marketing jargon and end up convinced the answer is a device with 'bells and whistles' - a device that has too many 'modes' so the user cant operate it properly when the pressure is on.



I very much agree with your principle that education is the key, safe travel techniques being the most important.



Also, that the sector should acknowledge the facts - close multiple burials are relatively rare - and improving shovelling technique is a potential life saver.

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