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(Photo: Gerhard Fitzthum/Getty Images)

How Could a Trail Fit for a Toddler Be the Site of a Deadly Disaster?

A fatal avalanche near Hoosier Pass, Colorado, is a reminder that dangerous slides can occur on gentle terrain

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On Saturday, January 8, Drake Oversen, 35, and Hannah Nash, 25, of Colorado Springs were killed in an avalanche near Hoosier Pass, about 20 minutes outside the ski town of Breckenridge. The couple had been snowshoeing with their dog, Valerie, that morning when they triggered a slide, and rescuers later found the bodies of all three buried beneath snow and debris.

The Colorado Avalanche Information Center (CAIC) published news of the tragedy alongside an aerial image of the avalanche. The photo grabbed my attention, and I immediately recognized the slide zone as the site of a family picnic I had organized in August.

I’d specifically chosen the area for its gentle terrain. The slope ascending from the highway is mellow, the hike is an easy out-and-back on a jeep road, and the entire route is within sight of a neighborhood. In my eyes, it was an ideal location for a hike with my two-year-old daughter.

I wondered, How could a trail fit for a toddler be the site of a deadly disaster?

Ethan Greene, director of the CAIC, told me the tragedy is yet another reminder that deadly avalanches sometimes occur on seemingly benign terrain under the right conditions.

“You don’t have to be ten miles into the wilderness or descending a fourteener to get caught in an avalanche,” he said. “There are certain times when even very small slopes are extremely dangerous. And we see bad accidents occur extremely close to roads and access points.”

According to the CAIC report of the incident, the slab of snow that killed Overseen, Nash, and Valerie was about 370 feet wide, ten feet deep, and 100 vertical feet long. It broke free from a snowfield on a slope that was between 35 and 38 degrees—that’s the pitch of an intermediate run at your local ski resort. The slab then rushed down to where Overseen and Nash were standing, on a 20-degree grade—the same pitch of a typical bunny slope.

We often see stunning videos of avalanches with massive cornices tumbling down sheer cliffs, or snowfields sloughing off into steep bowls. The slide that killed Overseen and Nash was not as dramatic as these but proved to be just as deadly. Greene said the most likely scenario is that the trio set off from the parking lot on Hoosier Pass and initially snowshoed along the jeep road, but at some point they lost the trail in the deep powder. When they came around a bend in the trail, they walked below the steeper hillside and likely remotely triggered the slide.

“It’s a small slope, but it’s steep enough,” Greene said. “In the current conditions, we’ve seen people trigger avalanches on lower-angle slopes than even that.”

Low-angle avalanche accidents like this require a convergence of snow conditions and human error, and they are common when there’s been heavy snowfall and strong winds after a period of dry and cold weather. In the Hoosier Pass slide, the hillside above the trail showed a layer of basal facets: incohesive snow that was formed early in the season. More recent storms buried that weak layer with feet of wind-deposited snow, and the conditions formed a huge slab on a leeward-facing slope above the trail.

With such a fragile makeup, slides can be triggered remotely. You don’t have to be standing on the steepest part of the slope for your weight to trigger the slide, explained Kelly Elder, a snow scientist with the U.S. Forest Service. You could just as easily be on the flats below it, as Overseen and Nash were.

“If there’s a failure in the basal layer, that motion can be carried in the layers above, like a ripple up the slope, to the area that actually fractures, and the whole thing may come unglued,” Elder said. “You can be on a relatively flat slope and still get caught by an avalanche that you have triggered.”

Fractures in the basal layer can travel for hundreds of yards and trigger slides on faraway hillsides. Bruce Tremper, the former head of the Utah Avalanche Center, said he has set off avalanches up to a quarter mile away while walking on flat ground.

Tremper said he’s also read multiple avalanche reports from low-angle slides that resulted in fatalities.

“It breaks my heart because it’s not their fault—they just don’t know about avalanches,” Tremper said.

Human error is the final deadly element in avalanches of this type. According to the CAIC report, neither Overseen or Nash were carrying avalanche beacons or backcountry rescue gear. Perhaps they—like myself—simply assumed that the jeep trail was safe for walking during all months of the year.

The Rocky Mountains are crisscrossed by a web of old mining roads and trails, many of which were built long before avalanche safety was of any concern. Hikers, snowmobilers, and snowshoers may assume routes like these are safe, since they are well-trafficked and close to major highways.

“If you assume a road bed is safe from avalanches, you are playing with fire,” Elder said.

And while avalanche education and safety devices are becoming more common among backcountry skiers and other groups that seek out steep, extreme terrain, even basic backcountry knowledge is often lacking with more casual groups, like snowshoers or suburban dads looking for a picnic spot.

The easiest solution, Elder said, is to learn some form of avalanche safety, look at local avalanche bulletins, and recognize that, in the mountains, it’s hard to go anywhere without some avalanche risk. Even mellow terrain and fire roads are frequently close enough to larger slopes to be a danger.

“Look at the avalanche forecasts for your area. If there are hazardous slopes and aspects in your area, steer clear of them,” Elder said. “You can’t just focus on what is at your feet—think about what’s above you, even if it’s far away.”

Lead Photo: Gerhard Fitzthum/Getty Images

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