Scientist hopes to forecast killer avalanches

In the winter of 2009, a massive avalanche started near the crest of the Garden Wall in Glacier National Park and ran 4,000 vertical feet down the slope, crossing the Going-to-the-Sun Road twice settling just below the access road to Packer's Roost.

In its wake, the avalanche left a path of destruction about 200 yards wide, heavily damaging the Sun Road and tearing out an historic guardwall.

The wet slab avalanche also took down trees that were more than 200 years old. Luckily no one was in its path, as it happened in the winter months.

The U.S. Geological Survey is hoping to better predict wet slab avalanches in Glacier Park, scientist Dan Fagre said at a talk in Apgar last week.

Wet slab avalanches are caused when water runs underneath an existing snowpack. The resulting slide is like wet concrete, taking out everything in its path.

They're most common in the spring months, when snows in the Park turn to rain. That's the same time crews are plowing the road, often right in avalanche chutes. The USGS hopes to give crews an early warning system for avalanche danger.

So before snows fell in the high country of the Park this fall, researchers put in special devices in known avalanche chutes called lysimeters to measure when the water begins running under the snowpack.

"The second it happens, we'll know," Fagre said. "And we can warn road crews to get out of there."

A few years ago, the USGS created an avalanche atlas of the entire highway, detailing every avalanche chute along its 50-mile length.

Park crews also use avalanche spotters to watch for slides while plowing the Sun Road. That works up to a point, but spotters often can't see the tops of avalanche chutes because of the terrain.