Set Limits
STEP 2: SET LIMITS ON THE GROUP'S EXPOSURE TO AVALANCHE TERRAIN.
As a part of Anticipating the Hazard, your group discussed your uncertainty regarding conditions and terrain options. The relationship between that uncertainty and your terrain travel is clear-cut: as uncertainty increases you want to reduce your exposure to avalanche terrain. Likewise, as the avalanche danger increases, you want to reduce your exposure to avalanche terrain.
To do this, choose a terrain mindset that helps place a limit on the acceptable exposure to avalanche terrain based on the danger and the uncertainty. Use the table below and in your fieldbook to designate one of three options:
Keep it simple and avoid avalanche terrain
Limit exposure
Step it out cautiously
When you Detail Your Terrain Plan in Step 3, you will apply these broad terrain limits to your specific terrain choices. The purpose of setting limits is two-fold: first, to improve your plan and second, to help you make more consistent choices about your exposure to avalanche terrain in the field. Constraining choices to within a range of appropriate limits before even heading outside will improve your group’s decision making and reduce the influence of difficult-to-manage biases.
Classifying avalanche terrain by exposure
Developed by Parks Canada and the Canadian Avalanche Association, the Avalanche Terrain Exposure Scale (ATES) is a tool that helps the user visualize the complexity of terrain and extent of exposure the user must manage when traveling in and around avalanche terrain. The ATES scale is presented in three broad, but overlapping categories; SIMPLE, CHALLENGING, and COMPLEX avalanche terrain.
These descriptors are included as a reference to use when describing the amount of exposure to avalanches a particular piece of terrain has. An initial approach to set limits to your group’s terrain use is to agree to not exceed a certain level of exposure for example, choosing to stick to “Simple” terrain for the day. Your discussion of the potential hazards should target where the hazard exists, assess your uncertainty with these conditions, and initiate the conversation of how your group can use terrain to reduce risk.
Some backcountry routes may have ATES ratings. In other areas you can reach out to local guides, forecasters, patrollers, or other avalanche experts to help you anticipate the level of exposure to avalanche terrain. Consider traveling with an expert capable of managing current conditions and more complex terrain as your group gains experience planning for and managing your exposure in the backcountry.
Descriptions and photos follow to provide an idea of broadly what Simple, Challenging and Complex terrain looks like. Visit this tutorial put together by Avalanche Canada to learn more.
An example of Simple terrain with areas of potential avalanche exposure marked.
SIMPLE TERRAIN features low angle or primarily forested terrain. Some forest openings may involve the runout zones of infrequent avalanches, but the terrain offers many options to eliminate or reduce exposure. When uncertainty is higher and group confidence is lower, the group should choose simple terrain in response. New partners, new riding area, and lack of familiarity with conditions, such as an unusual avalanche problem, all warrant opting for simple terrain.
An example of Challenging terrain with areas of potential avalanche exposure marked.
CHALLENGING TERRAIN will present your group with exposure to well defined avalanche paths, start zones, or terrain traps, but options exist to reduce or eliminate exposure with careful route finding.
As sources of uncertainty decrease, and conditions improve, your group may choose to increase your exposure to selected steeper terrain.
An example of Complex terrain with areas of potential avalanche exposure marked.
COMPLEX TERRAIN features steep slopes, few trees, and overlapping avalanche paths where your group will find that minimal options exist to reduce exposure. On days when everything aligns, and group confidence in conditions is high, stepping out cautiously into complex terrain can be an option.