The Avalanche Terrain Exposure Scale (ATES)

ATES is the Avalanche Terrain Exposure Scale. ATES was developed in Canada by Parks Canada and the Canadian Avalanche Association. It is designed to give users information on the level of exposure to avalanche hazard when they go into uncontrolled avalanche terrain. ATES has been adopted in New Zealand by the Mountain Safety Council and the Department of Conservation (DOC).

It is important to note that ATES is independent of snowpack stability. The terrain class remains the same no matter what the snowpack stability is. By using ATES, you can begin to measure your skills, experience, and risk tolerance against the terrain you plan to travel in. Reading both ATES (where available) and the NZAA forecast helps you to decide on suitable trip objectives.

When the avalanche advisory is rated 'moderate' or above, it is advised to select terrain more conservatively. Alternatively, when the avalanche advisory is rated ‘low’, this might be an opportunity to consider more challenging terrain you have been contemplating while keeping in mind the specific snowpack concerns at the time. The two scales can be used together to appropriately manage your risk in the backcountry.

ATES ratings are intended as a supplement to your pre-trip planning material. When planning your trip, read the guidebook, study maps and photos, talk to friends, check weather and NZAA forecasts, and refer to the ATES ratings if they are available. This combination will give you a better sense of the route you are choosing.

Avalanche Terrain Exposure Scale (ATES)

Description	Class	Terrain criteria
Simple	1	Exposure to low-angle or primarily forested terrain. Some forest or bush openings may involve the run-out 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 route finding. 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.

Description

Class

Terrain criteria

Simple

1 Exposure to low-angle or primarily forested terrain. Some forest or bush openings may involve the run-out 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 route finding.

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.

ATES can be applied to:

a fixed feature such as a track or marked route
an unmarked route
to parts of catchments or ranges
entire catchments or ranges

It is important to be clear about what scale it is applied to because this could affect how you interpret the rating. When an ATES assessment is done of a catchment or mountain range it is likely that the area has within it a mixture of simple, challenging, and complex terrain. The finer the scale used, the more definite things will be.

As an example, a mountain range may generally be ‘challenging’ but contain areas of ‘complex’. It still meets the definition of ‘challenging’ because there are options for avoiding avalanche paths. If there's a particular valley in the range where there is no option for avoiding avalanche terrain then that place is ‘complex’.