Analysis of the Durrand Glacier Avalanche Accident

Durrand Avalanche Report page 18
2. Dry slab avalanches rarely move beyond a 25° avalanche shadow zone (that is, they rarely
have less than a 25° alpha angle). This means that ski tourers can stay reasonably safe by
staying outside of this shadow zone. In this case, much of the uphill track was within the
25° avalanche shadow zone below the west ridge of Tumbledown Mountain, which would
explain why all the avalanches that occurred crossed the skier’s uphill track.
P. Nature of the underlying ground in the La Traviata couloir
1. From limited exposures observed during a site visit in June, 2003, it appears that the
underlying ground in the La Traviata couloir is covered with colluvium, derived from the
rocks above. Most of this material is relatively fine textured, suggesting that the surface
roughness depth would be less than 50 cm, and probably less than 20 cm. There are no
trees, bluffs, large rocks, or other features that would provide obstacles to the flow of snow
down the slope. A shallow draw running east down the slope (perpendicular to the fall line)
is located about 70 metres from the base of the slope. Some avalanche debris appears to
have cascaded into this draw, but most of it stopped just before it.
Q. Initial response to the avalanche
1. Ruedi Beglinger was above the La Traviata couloir, and some distance off to the east side
when the avalanche occurred. It was not possible to determine exactly where he was, but
most likely, it was about 70 metres north northeast of the slide scarp. One skier estimates
that he was about 20 metres from the next person in the track, and that person was about
50 metres up beyond the avalanche head scarp at the top of the couloir.
Crown at convex
roll-over
Fatal avalanche
Dominant wind direction
Guide’s
position
June 19, 2003
Fig. 18: Top portion of the La Traviata couloir, and lower angled ground at the top east.
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