Symbole d'avalanche

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The Avalanche Terrain Exposure Scale (ATES) is a new development from Parks Canada, which offers an avalanche classification system based on the landscape – not the snow. The system presents two models: technical, and public communication.

The technical model has been designed for users trained and skilled in the subtle nuances of avalanche terrain. The public communication model is designed for communicating technical concepts to the public, who is largely unable to comprehend the technical details. Both scales represent the same thing – spoken in two languages.

The ATES can be applied at whatever scale is appropriate. Parks Canada has chosen to link with popular guidebooks, and apply ATES ratings to backcountry trips, which are well described in these books. This classification could however, be applied to any given piece of terrain – it is all a question of scale.

Avalanche Terrain Exposure Scale defined
Technical Model (v.1-04)
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
(events:years)
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.

Mount Revelstoke and Glacier terrain

Avalanche Terrain Ratings for backcountry touring in the Mountain National Parks
Name Park Class
2km & 5km Loop trails Mount Revelstoke National Park Simple - Class 1
3 Pass Traverse Glacier National Park Complex - Class 3
8812 Bowl Glacier National Park Complex - Class 3
Asulkan Hut/Tree Triangle Glacier National Park Complex - Class 3
Asulkan Pass Glacier National Park Complex - Class 3
Asulkan Valley Practice Slopes Glacier National Park Complex - Class 3
Avalanche Crest - to treeline Glacier National Park Challenging - Class 2
Avalanche Crest bowl/slidepath Glacier National Park Complex - Class 3
Balsam Lake to Eva & Miller Lakes Mount Revelstoke National Park Challenging - Class 2
Balsam Lake to Mt Revelstoke Summit Mount Revelstoke National Park Challenging - Class 2
Balu Pass Glacier National Park Complex - Class 3
Beaver River Glacier National Park Simple - Class 1
Bonney Glacier Glacier National Park Complex - Class 3
Bruins Pass Glacier National Park Complex - Class 3
Cheops Glades Glacier National Park Challenging - Class 2
Clachnacudain Creek Mount Revelstoke National Park Complex - Class 3
Clachnacudain Creek east fork Mount Revelstoke National Park Complex - Class 3
Clachnacudain Glacier-Inverness Peaks Mount Revelstoke National Park Complex - Class 3
Cougar Valley Glacier National Park Complex - Class 3
Coursier Creek Mount Revelstoke National Park Complex - Class 3
Dome Glacier Glacier National Park Complex - Class 3
Flat Creek slidepaths Glacier National Park Complex - Class 3
Flat Creek valley trail Glacier National Park Challenging - Class 2
Fortitude Glacier National Park Complex - Class 3
Glacier Circle Glacier National Park Complex - Class 3
Grizzly Shoulder Glacier National Park Challenging - Class 2
Grizzly/Little Sifton Traverse Glacier National Park Complex - Class 3
Hamilton Creek Upper Meadows Mount Revelstoke National Park Complex - Class 3
Hermit Meadows Glacier National Park Challenging - Class 2
Illecillewaet Neve access Glacier National Park Complex - Class 3
Illecillewaet Practice Slopes Glacier National Park Complex - Class 3
Inspiration Woods Mount Revelstoke National Park Simple - Class 1
Lily Glacier Glacier National Park Complex - Class 3
Lindmark Trail above Parkway Intersection Mount Revelstoke National Park Challenging - Class 2
Lindmark trail to Parkway Intersection Mount Revelstoke National Park Simple - Class 1
Lizards Tail Glacier National Park Complex - Class 3
Lookout Col Glacier National Park Complex - Class 3
Maunder Creek Mount Revelstoke National Park Complex - Class 3
McGill Bowl - McGill Pass Glacier National Park Complex - Class 3
McGill Shoulder Glacier National Park Challenging - Class 2
Meadows in the Sky Parkway Summit Trail to 8 Mile Crossing Mount Revelstoke National Park Simple - Class 1
Mount Klotz above treeline Mount Revelstoke National Park Complex - Class 3
Mt. Rogers Glacier National Park Complex - Class 3
Mt. Swanzy Glacier National Park Complex - Class 3
Mt. Tupper Traverse Glacier National Park Complex - Class 3
NRC Gullies Glacier National Park Complex - Class 3
Perley Rock Glacier National Park Complex - Class 3
Rogers Pass Ski Hill (forest cuts behind hotel) Glacier National Park Simple - Class 1
Saint Syr Creek Mount Revelstoke National Park Complex - Class 3
Sapphire Col Glacier National Park Complex - Class 3
Sifton Col Glacier National Park Challenging - Class 2
Smart Ridge Glacier National Park Complex - Class 3
Steps of Paradise - Youngs Pk Glacier National Park Complex - Class 3
Summit Trail above 8 Mile Crossing Mount Revelstoke National Park Challenging - Class 2
Terminal Peak Glacier National Park Complex - Class 3
The Cone Glacier National Park Complex - Class 3
The Hourglass Glacier National Park Challenging - Class 2
The Mouse Trap Glacier National Park Complex - Class 3
The Ravens Glacier National Park Complex - Class 3
Ursus Major Glacier National Park Complex - Class 3
Ursus Trees Glacier National Park Complex - Class 3
Vaux Moraines/Sir Donald/Uto Col Glacier National Park Complex - Class 3
Vent Shaft slopes Glacier National Park Complex - Class 3
Video Peak Glacier National Park Complex - Class 3
West Woolsey Creek Mount Revelstoke National Park Complex - Class 3
Wheeler Hut approach and vicinity Glacier National Park Simple - Class 1
Woolsey Creek Road Mount Revelstoke National Park Challenging - Class 2
Woolsey Glacier-Coursier Peak Mount Revelstoke National Park Complex - Class 3
Youngs Pk via Illecillewaet Glacier National Park Complex - Class 3