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Chilkoot Trail National Historic Site of Canada

 Log Cabin Mountain ATES

Log Cabin ATES
 Log Cabin Mountain ATES
© Parks Canada

ATES Ratings

Description   Class  Terrain Criteria
 Simple  1  Exposure to low angle or primarily forested terrain. Some forest openings may involve the runout zones of infrequent avalanches. Many options to reduce or eliminate exposure. No glacier travel.
 Challenging  2  Exposure to well defined avalanche paths, starting zones or terrain traps; options exist to reduce or eliminate exposure with careful routefinding. Glacier travel is straightforward but crevasse hazards may exist.
 Complex  3  Exposure to multiple overlapping avalanche paths or large expanses of steep, open terrain; multiple avalanche starting zones and terrain traps below; minimal options to reduce exposure. Complicated glacier travel with extensive crevasse bands or icefalls.

Technical Model (v.1- 04)

The technical model has been designed for users trained and skilled in the subtle nuances of avalanche terrain.

   1 - Simple  2 - Challenging  3 - Complex
 Slope angle  Angles generally < 30º  Mostly low angle, isolated slopes >35º  Variable with large % >35º
 Slope shape    Uniform  Some convexities  Convoluted
 Forest density    Primarily treed with some forest openings  Mixed trees and open terrain  Large expanses of open terrain. Isolated tree bands
 Terrain traps  Minimal, some creek slopes or cutbanks  Some depressions, gullies and/or overhead avalanche terrain  Many depressions, gullies, cliffs, hidden slopes above gullies, cornices
 Avalanche frequency
 1:30 ≥ size 2  1:1 for < size 2
1:3 for ≥ size 2
 1:1 < size 3
1:1 ≥ size 3
Start zone density  Limited open terrain  Some open terrain. Isolated avalanche paths leading to valley bottom  Large expanses of open terrain. Multiple avalanche paths leading to valley bottom
 Runout zone characteristics  Solitary, well defined areas, smooth transitions, spread deposits  Abrupt transitions or depressions with deep deposits  Multiple converging runout zones, confined deposition area, steep tracks overhead
 Interaction with avalanche paths  Runout zones only  Single path or paths with separation  Numerous and overlapping paths
 Route options  Numerous, terrain allows multiple choices  A selection of choices of varying exposure, options to avoid avalanche paths  Limited chances to reduce exposure, avoidance not possible
 Exposure time  None, or limited exposure crossing runouts only  Isolated exposure to start zones and tracks  Frequent exposure to start zones and tracks
 Glaciation  None  Generally smooth with isolated bands of crevasses  Broken or steep sections of crevasses, icefalls or serac exposure

Using this scale

 Any given piece of mountain terrain may have elements that will fit into multiple classes. Applying a terrain exposure rating involves considering all of the variables described above, with some default priorities:

  • Terrain that qualifies under an italicized descriptor automatically defaults into that or a higher terrain class. 
  • Non-italicized descriptors carry less weight and will not trigger a default, but must be considered in combination with the other factors.