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


In this section, we deal with the very volitile issue-of avalanche hazard catagories. Here are three-viewpoints, as well as a European perspective:

Let the Hazard Begin: a short history

by Knox Williams

Avalanche forecast programs began popoing up in several western states in the early 1970s. In 1973, the U.S. Forest Service Colorado Avalanche Warning Program began operation. It was the first statewide avalanche forecast program in the United States. There were several other forecast programs operating at about this same time--one for the Jackson Hole area of Wyoming, and one for Cottonwood Canyons in the Wasat~h Range in Utah. These, too, were Forest Service operations.

For many years, the Forest Service had been issuing fire danger ratings and had been using the adjectives "low, moderate, high, and extreme" to describe the relative hazards. It was logical for the Forest Service avalanche forecasters to adapt these terms to describe avalanche hazards. So, the early avalanche programs used a common terminology to relate avalanche hazaards, yet there were no written definitions of the terms "low, moderate, high, and extreme." It quickly became apparent that some national standars needed to be set, for it would be a public disservice if, for example, Colorado's "high avalanche hazard" was the same as Utah's "moderate avalanche hazard."

In the fall of 1975, the Northwest Avalanche Center was set to open in a few months, and avalanche forecasters met in Seattle to discuss common problems and goals of the various hazard categories. The goal was to define the terms simply (no jargon), briefly (20 words or less), and universally (no regional bias). They had to be useful to the forecasters, the public, and the news media. A media consultant sat in on the meeting to offer wisdom and advice from the media's point of view.

For better or worse, the following definitions came out of this meetimg and have been used now for 13 years:

Low: Mostly stable snow. Avalanches are unlikely except in isolated pockets on steep snow-covered slopes and gullies.

Moderate: Areas of unstable snow. Avalanches are possible on steep, snow-covered open slopes and gullies.

High: Mostly unstable snow. Avalanches are likely on steep snow-covered open slopes and gullies.

Extreme: Widespread areas of unstable snow. Avalanches are certain on some steep snow-covered slopes and gullies. Large destructive avalanches are possible.

A controversy over the value of this system began shortly after it was introduced and continues today. Some forecasters found the system too general, and tried adding more categories such as "lowmoderate" and "moderate-high". Some tried adding more detail to the definitions (and then retreated when they found themselves too restricted). Some have tried to fine-tune the definitions by separating the likelihood of natural versus triggered releases. Some use elevation, aspect, and slope angle to differentiate between hazard categories. Some hate the word "pockets". Some hate the word "moderate". Some say replace the word "hazard" with the word "instability". Some hate the system and think the public doesn't understand it, so they don't use it. Some like the system and think the public likes it, so they use it.

No doubt, the list of likes, and dislikes, tweaks, and slam-dunks goes on. What else can be expected when you try to define that which is so little understood? Certainly we in the Colorado Avalanche Information Center have been grappling with this issue for many years and have debated many of the controversial points raised above, but we have continued to use the basic definitions created in 1975. A good part of our reason for doing so was that we felt the public was making the system work.

Indeed, we surveyed our customers in the 1986 and found overwhelming support for this hazard rating system: 83 percent said that the ratings were "mostly" or "absolutely" helpful to"them, while only 2 percent found them "not at all" helpful. With this level of reinforcement, we will continue to provide the public our hazard assessments ...while always seeking a better mousetrap.

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