96 killed in unknown avalanche

The Avalanche Review, VOL. 6, NO. 4, MARCH 15, 1988
Copyright © All Rights Reserved; AAA

96 Killed in Unknown Avalanche
contributed by Sue Ferguson

The Wellington avalanche disaster near Stevens Pass, Washington, which killed 96 people in 1910, released from a slope that had never before avalanched. According to Thorton T. Munger in his 191 1 USDA-FS Circular #173, "The path of this avalanche was down a hillside which was originally well covered with a heavy stand of timber, and which was severely burned over in 1893 by a fire which completely killed the forest. Twice since then fire has run over the slope, so that at the time of the avalanche it was bare, except for a few logs, some stubs, and a very little brush. The slope was exceedingly regular and smooth, is devoid of ledges, and is crossed by but one small gully. The avalanche originated at an altitude of about 3,800 feet, on a grade of about 75 per cent (36 deg)."

Munger goes on to state that, "The whole length of its course was not over 1,600 feet, yet where it crossed the railroad near its terminus it was 1,000 ft wide. Its length, therefore, was not very much greater than its width. It descended about 950 feet along an average gradient of 69 per cent (34deg). This is the first slide known to have occurred on this slope, for it had been but a few years since it has been deforested sufficiently to allow the snow to slide. even then, it took exceptional weather conditions to promote it. Munger describes a slope-slide as "a wide, shallow, rather slowly moving mass of snow, which breaks loose from the snow mantel higher up on the mountain side, and which, starting to slide, involves the snow of the whole side hill, and slips down the slope without converging into a canyon. It may be likened, in fact, to a mass of wet snow sliding in a body off the roof of a large building after a sudden thaw."

This is in contrast to "canyon slides" which Munger says "originate on a steep and rocky cliff at the head of a canyon or gully, and follows down the depression as a compact, narrow body of snow, constantly increasing in volume as it descends. It is often composed of a number of little slides which come off the steep, rocky sides of the canyon, and, converging, follow down the main canyon as in a trough, usually at great velocity."

Unlike canyon-slides, Munger believes slopes-slides are unnecessary and preventable. He outlines four principles to follow in order to lessen the frequency of destructive avalanches. These principles are:

(1) Proper care of the area now forested.
(2) Exclusion of grazing.
(3) Careful cutting of timber on steep slopes.
(4) Reforestation of denuded areas.

Since 1910 the Wellington slide path has developed a healthy maturing stand of trees over much of its slope. There is now only a small gully that routinely avalanches snow onto the abandoned snow sheds. An 8 mile train tunnel through the mountain was built shortly after the fatal slide to avoid subsequent disasters. Slopes adjacent to the Stevens Pass highway are now protected from clear cut style logging by a scenic corridor act. No grazing is permitted in the area and destruction by fire is greatly diminished by modern fire-fighting methods.

This does not mean that slopeslides have been eliminated from the Northern Cascades. On the contrary, there are still nearly 100 recognized avalanche path in the Steven Pass transportation corridor and recreation area. All have the potential for destruction. Nearly 40% are what Munger calls slope-slides. One of these is, appropriately named "Clear Cut". Another is called "Tree Farm" for it is an old slide path that is beginning regrowth.

Thorton Munger's 191 1 description of the roles that forest cover and topography play in the formation of avalanches was farsighted and are still applicable in today's alpine forest policies.

Thanks to Professor Grant W. Sharpe of the University of Washington College of Forest Resources for bringing Munger's article to our attention.