Also: Chute, Gully, Couloir d’avalanche
A couloir is a steep and narrow vertical gully on a mountainside, typically with rocky sides to it. These are often used as climbing and steep skiing routes. They may be subject to cross loading in addition to windloading at the top, new snow, and other more typical factors. The energy balance at the surface may also be different from open slopes near by.
The safest season to climb or ski couloirs is spring. There is not a lot of opportunity to assess the snowpack conditions until the person or group is fully committed to the route. This is a common situation for climbers in spring and is the basis for our Climbers Avalanche Course. That course is specifically tailored to advance planning rather than assessing things enroute, which is often or usually not an option for climbers.
Advance planning is also essential since escape routes or other options to mitigate consequences are almost always limited or non-existent. Couloirs are a type of terrain trap.
Chute and couloir mean the same thing for all practical purposes. A gully is a somewhat more general term and some gullies are not steep enough to be called a couloir or chute.
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