Assessing Avalanche Threats and Factors

• Buffer
• Tweet

Masses of snow, or snow and ice that loosens and suddenly slides down a mountain, are called avalanches, and they have the potential to be fatal. Thus, those who like to venture into the alpine learn to read the clues nature gives to assess when an avalanche may occur. In fact, avalanches are measured in terms of the level of risk that an avalanche may occur.

Factors Used to Assess the Threat of an Avalanche

Assessing the risk of an avalanche is not a simple process. It involves complex judgment based on expert forecasts, personal experience, and up-to-the-minute weather changes. Among the numerous variables that go into assessing a terrain for the possibility of an avalanche are:

slope steepness
wind speed
wind direction
current temperatures
humidity
weather pattern history
snowfall
the stability of the snow pack
exposure to the sun
timeframe

Moreover, these variables change change on a weekly, or even hourly basis, with some of the factors being different from one area to another area, as well.

Avalanche Danger Levels and Avalanche Bulletins

To measure the risk of an avalanche occurring, avalanche bulletins are issued by alpine experts and dispersed worldwide. They provide information on all of the the latest weather conditions and snowpack conditions, as well as travel advice and current alpine activity that should be watched. These avalanche advisories, or avalanche forecasts, include danger ratings on a five-leve, international avalanche danger scale. The five danger levels are: low, moderate, considerable, high, and extreme. Each level includes a description of probably avalanche activity, as well as a description of probability, distribution, and possible triggers.

At the low level of threat, natural and human-triggered avalanches are unlikely, so travel is considered to be generally safe. At the considerably level, natural and human-triggered avalanches are possible, and as a result, caution is emphasized in these areas. On the far end of the scale, at the extreme danger level, widespread avalanches are certain to happen, and therefore travel in this area of terrain is to be avoided at all costs.

Resources For Avalanche Danger Levels

Information from the National Academies Press

Assessing Avalanche Threat on the Ground

While the danger scale is widely used, it essentially only provides an overall guide that should be supplemented by real-time evaluation of the conditions experienced on the ground. Other factors should be assessed in order to measure the risk of an avalanche. The first is the steepness of the slope, or the slop angles. Most avalanches occur on intermediate slops of approximately 35 to 45 degrees. This is the steepness that is frequented by skiers and snowboarders. However, even mild slopes can pose a danger if they are connected to steeper terrain above.

The second consideration is the tender spots, or stress-concentrated areas. These include sudden increases in the angle of the slop, windy areas, spots with thin snow cover, and rollovers. Slope anchors can improve some of these areas and include fallen branches, logs and rocks that protrude from the snow. These elements help hold snowpacks in place, making it less likely to slide.

Conditions can also change depending on the geographical location. Shady, north-facing slopes produce more avalanches in the winter. But south, sun-facing slopes produce wet avalanches in the spring. Areas that receive only a moderate amount of sunshine tend to be more stable overall.

The Munter Reduction Method and 3×3 Filter Method for Avalanche Threat

In Europe, alternative ways to measure an avalanche were created by Werner Munter. Munter’s Elementary Reduction Method is geared toward facilitating quick decision making, and entails avoiding certain slope angles based on the avalanche forecast. For example, a moderate danger level means that one should not travel on slopes angles that are steeper than 40 degrees. A considerable danger level means that travel should be avoided on slopes steeper than 35 degrees, and so on.

Munter is best known for his 3×3 Filter and Reduction Method. This method calculates whether a forecasted danger level can be reasonably reduced by evaluating it from three vantage points: regional, local and slope. The actual formula is: Danger/Reduction = Risk.

Lastly, those who enjoy alpine recreation can use the Red/Green Light method to assess the likelihood of an avalanche hazard. This process takes into consideration the interrelationship between terrain, weather, snowpack, and the human factor. Each factor is thought of as a red, green, or yellow light, according to the hazard level symbols. G, for green, means that it go. Yellow, or Y, means that there is potential danger and caution should be exercised. And R, for red, means that one should stop, as danger is certain.

Resources About Avalanches and Avalanche Threat Assessment

Avalanche Measurement, US Deaths, and Resources
Avalanche Risk Assessment Information from Harvard and NASA
Information in a PDF from the State of Montana About Avalanche Weather and Threat Assessment

Resource by AnnaBelle

Annalise Kaylor is a freelance writer, editor, and consultant specializing in search engine optimized content for the web. As a writer, her work has appeared across the United States in print ads for Whirlpool, Maytag, Home Depot, and Lowe's, among others. As a consultant, she has worked primarily in the education sector, helping universities increase their web visibility and construct and implement social media strategy. Annalise is an avid reader, knitter, organic gardener and baker, as well as the author of the popular baking blog, Knead To Be Loaved. Annalise enjoys fly fishing, camping, and hiking.

Related Research For Teachers, Students, and Kids