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Assessing danger

Avalanche Days come at a crucial time
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Lifelines Simon Gravel sets an avalanche beacon to receive. Along with a beacon, a probe and shovel are essential backcountry survival tools.

Whither Ullr? The Norse snow god, usually depicted on skis with a bow and arrow, has not only left the resort, but, it appears, the entire province.

Revered for sprinkling white fluff across winter wonderlands the world over, Ullr is also something of a protector, the god with the shield. And yet, this winter has seen a staggering number of backcountry avalanche deaths — 13 in less than a month.

Figures like that make the annual Avalanche Awareness Days (AAD) rather topical. Though AAD’s main hoorah went down in Revelstoke last weekend, related events played out in snow spots across Western Canada, from Banff to Squamish. B.C. Parks Ranger Aaron Donohue, with colleagues Simon Gravel and Mark Latham, were the local point guards for the event, and they set up a demonstration at Red Heather Lodge, a little over five kilometres up Garibaldi Provincial Park.

And it was snowy up there. The trees were heavy with it, almost lazy with it, slumping across the trail here and there. And the temperature was mild, a fact Donohue deposited in the back of his mind. If you see balls of snow tumble from trees or roll down chutes, you make a note of it. It’s a sign of warming temperatures, nothing to ring the alarm over, not right away, but something to remember. Warming trends, after all, cause the snowpack to weaken.

And you need to understand the snowpack if you’re going to venture into the backcountry. That’s why Donohue dug out a two-metre cross section behind the lodge.

“Picking where you dig the snow pit is a big part of evaluating the snowpack,” he said, a small assembly of snowshoers, skiers and other backcountry enthusiasts gathered round.

For example, a bad spot would be directly under a tree, where falling snow has impacted the pack.

Donohue’s snowpack acts as a record of the season’s snowfalls. You can see a rain crust from early January’s deluge, and, beneath that, you can see December’s bountiful offerings compressed by the weight of what’s above. That rain crust could pose a problem. So could the ice crust a ways beneath it.

“That provides a good surface for snow to slide on,” he said. “(But) this pit isn’t representative of stuff out there. Ever.”

He’s talking about anywhere else. Variability is a major factor when trying to gauge the likelihood of an avalanche. Even on the same slope, even just a short distance away, there can be a lot of variability in the snowpack.

Often, your eyes aren’t enough. Sure, you can see the different layers — but how cold are they? The ground temperature is usually around zero degrees Celsius, even if the surface is minus-40. The surface was above zero that day, and mid temperature was minus-10 — though it will start to equalize as the winter wears on.

“So the snow’s just sitting there, and crystals aren’t going to form as rapidly,” he says. Crystals are caused as moisture travels upwards. And they don’t stick. “When you have that less than 10 degrees difference per metre, that tells you that, within the snowpack, things are bonding and it’s pretty much stable.”

There are other cues. Don’t be riding on the site of a recent avalanche. If you hear a “whumping” noise, that means a layer of the snowpack just collapsed. Cornices, pillows and drifts are tempting, but they’re a result of wind loading, which is sketchy business. If you hear a drum-like sound, it could mean there’s a weak layer underneath you. And new snow, god love it, is dangerous, especially a lot of it.

But let’s say you screw all that up. Let’s say you miss all those signs. There are a few different types of avalanches. There’s a loose snow avalanche, which occurs on the surface and is usually associated with spring; these are seldom fatal. There’s an ice fall avalanche. These occur when a glacier ice breaks off, a result of moving over a cliff. There’s a cornice avalanche, which is triggered when someone carves a snow wave too close to the edge. And there’s a slab avalanche, which is triggered by a disturbance in the snowpack; it’s typically the most fatal.

Let’s say you bring down part of the mountain on you or your friends. What do you do?

First, you better be equipped. You need a shovel, a pole and a beacon. If you don’t have that stuff, and know how to use it, you shouldn’t be in the backcountry. If you do have it, but aren’t too sure how to use it, go find Gravel, the ranger who held up the beacon demonstration last weekend.

Beacons can be set to receive or transmit signals. If you haven’t been buried, set yours to receive and follow the beeps. They aren’t super accurate, so you’ll need your pole to probe the snow in search of your friends.

“And then you start digging as fast as you can,” said Gravel. “The best chance to save your buddy is you. If you go down the valley and talk to search and rescue, they consider that a body recovery. After an hour, a person could be dead.”

And nobody wants that.

Gravel, Donohue and Latham all have extensive backcountry experience. Still, they’re careful not to call themselves experts. Training is always available through outfits like the Canadian Avalanche Centre. Spend enough time in the backcountry, and you will need it.

Latham has been caught in a couple avalanches over his time. “They weren’t burials, though. Just the sluff.”

Which is lucky.

“I’ve been backcountry skiing for about 10 years,” says Donohue. “The closest I’ve come is crossing an unstable chute. You don’t want to spend a lot of time on them. You want to mitigate the risk.”

He crossed quickly enough, but his buddy was a little slower. Thirty seconds after his friend traversed, the chute came down.

“You feel the power of an avalanche,” said Gravel, “even if it’s slow and not very strong, you feel it.”