Avalanches are part of life in the mountains. They can occur in any season, but are more common in winter and spring. Anytime that snow and steep slopes are combined there is potential for an avalanche.
You are taking a risk
If you travel through backcountry terrain exposed to avalanches, you must accept that you are taking a risk. You need to understand these risks before setting out.
Avalanche Terrain Exposure Scale (ATES)
ATES is independent of stability. The terrain class remains the same no matter what the snow stability is.
Terrain does not change with the weather. The angle and shape of the ground or the number of established avalanche paths do not vary. By using the ATES you can begin to measure your skills, experience and risk tolerance against the terrain you plan to travel in.
Avalanche Terrain Exposure Scale (ATES)
|Description ||Class ||Terrain criteria
||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.
||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 straight forward, but crevasse hazards may exist.
||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.
New Zealand Avalanche Advisory (NZAA)
New Zealand Avalanche Advisory
The traditional model for rating avalanche danger in New Zealand is the NZAA which is based on the stability of snow. The advisory may be updated on a daily basis as stability changes regularly through weather changes and storms.
The NZAA is provided by the Mountain Safety Council, and is available on the New Zealand Avalanche Advisory website and at DOC visitor centres.
You need both ATES and NZAA
Reading both ATES and NZAA helps you to decide if your trip is worth the risk.
When the avalanche advisory is rated 'moderate' or above, you should select very conservative terrain. Alternatively, when the avalanche advisory is rated ‘low’, it might be appropriate to consider that next level of terrain you have been contemplating.
The two scales must be used together to appropriately manage your risk in the backcountry.
These ratings are intended as a supplement to your pretrip planning material. When planning your trip, read the guidebook, study maps and photos, talk to friends, check weather and avalanche conditions, and refer to the ATES ratings. This combination will give you a better sense of the route you are choosing.
Experience you need for your trip
- Simple (Class 1) terrain requires common sense, proper equipment, first aid skills, and the discipline to respect avalanche warnings. Simple terrain is usually low-avalanche risk, ideal for people gaining backcountry experience.
- These trips may not be entirely free from avalanche hazards. On days when the NZAA is rated "considerable" or higher, you may want to re-think any backcountry travel that has exposure to avalanches, e.g. stay within the boundaries of a ski area.
- If there is no advisory, you or someone in your group should have done an avalanche-awareness course.
- Challenging (Class 2) terrain requires skills to recognize and avoid avalanche-prone terrain - big slopes exist on these trips. You must also know how to understand avalanche advisories, perform avalanche self rescue, basic first aid, and be confident in your route-finding skills.
- In places where an avalanche advisory exists, you should take an avalanche course prior to travelling in this type of terrain.
- If there is no advisory you or someone in your group should have done a four-day avalanche course.
- If you are unsure of your own, or your group’s ability to navigate through avalanche terrain - consider hiring a professional guide, normally an NZMGA qualified guide.
- Complex (Class 3) terrain demands a strong group with years of critical decision-making experience in avalanche terrain. There can be no safe options on these trips,
forcing exposure to big slopes.
- A recommended minimum is that you, or someone in your group, should have taken a four-day avalanche course and have several years of backcountry experience. Be prepared! Check the avalanche advisory regularly, and ensure everyone in your group is up for the task and aware of the risk.
- If there is no advisory, then it is recommended that everyone in the group has done the four-day course. This is serious country – not a place to consider unless you’re
confident in the skills of your group.
- If you are uncertain, hiring a professional NZMGA qualified guide is recommended.
Be avalanche aware!
If you are going into places avalanches could occur, make sure you:
- have checked the ATES class for where you want to go and the NZAA for the avalanche rating
- have the skills for the ATES class you are going into
- take an avalanche transceiver, a snow shovel and a probe. Know how to use these tools.