How to Assess Terrain for Avalanche Danger

Learning about terrain evaluation is an important aspect of backcountry travel. In some cases, there will be a large difference in snowpack stability within only a few yards. Being familiar with hazardous terrain allows you to address other concerns, such as snowpack stability, weather patterns and route choice.

Instructions

Difficulty: Moderate

Things You’ll Need:

• Winter Outerwear
• Avalanche Beacon
• Avalanche Probe
• Backcountry Snow Shovel
• Backpacks

1. Measure the slope angle (see "How to Assess Slope Inclination for Avalanche Danger," under Related eHows). A slope that's between 25 and 60 degrees is capable of producing a slab avalanche. The most dangerous angles are between 35 and 45 degrees. Keep in mind that even a mild slope can be dangerous if it's connected to steeper terrain above you.
2. Be aware of the slope's orientation related to solar radiation. The areas that receive moderate amounts of sunlight tend to be stabler than those completely shaded or those that end up in the sun for great lengths of the day.
3. Notice the aspect of terrain in relation to wind. A leeward slope is the side of a ridge where the wind deposits snow and most cornices form. The snowpack on a leeward slope is less stable than surrounding terrain because of the extra weight or "load" from the additional snow. Conversely, the windward slope, where snow has been removed by wind, is stabler because the snowpack has less of a load affecting it.
4. Look for evidence of slope anchors. A snowpack sitting on a smooth surface such as grass or a rock slab is much more likely to slide than an area with logs, trees and large boulders.
5. Notice the shape of the slope. The fractures where avalanches start are often convex in shape, like the back side of a spoon. A mild pitched slope, such as the top of a ridge, dropping into steeper terrain is an example of a convex slope.
6. Watch for avalanche clues from past months and seasons. Areas with broken tree limbs, small trees in the midst of a forest, and open slots on steep terrain are all signs of previous avalanches.

Tips & Warnings

• When you happen upon evidence of a recent avalanche, inspect the slide path to see what sort of terrain factors had a role in causing it. This is a good way to play snow detective and increase your eye for unstable conditions. Be certain to remain a safe distance from the slide area if conditions might produce additional avalanches.
• The risks of avalanches are extremely high in many backcountry situations across the country. The eHows on avalanche assessment are designed to increase your awareness and help you make safe decisions. However, a class on the subject or traveling with a guide is recommended for those new to the backcountry experience.