Analysis of the Durrand Glacier Avalanche Accident

More documents

Recommendations

Info

Durrand Avalanche Report page 17 N. Size of the fatal avalanche 1. If the area of snow that became mobilized is used, the volume of snow involved in the avalanche would be about 52 500 cubic metres (125 m wide on average x 280 m long x 1.5 metres deep). If a typical avalanche snow density of 0.4 tonnes per cubic metre is used, the mass of snow in the slide by this calculation would have been about 21 000 tonnes. 2. The Canadian avalanche size classification system uses mass, typical path length, and typical impact pressures to define size. Size Description Typical Mass (tonnes) 1 Relatively harmless to people 2 3 4 5 Could bury, injure or kill a person Could bury a car, destroy a small building, or break a few trees Could destroy a large truck, several buildings, or a forest with an area up to 4 hectares Largest snow avalanches known. Could destroy a village or a 40 ha forest Typical Path Length
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. Copyright: no part of this report may be reproduced without the written permission of the author.
Page 1 and 2: Analysis of the Durrand Glacier Ava
Page 3 and 4: Executive Summary page 2 The destin
Page 5 and 6: Executive Summary page 4 (e) There
Page 7 and 8: Table of Contents page 2 Figure 14
Page 9 and 10: Durrand Avalanche Report page 2 Dan
Page 11 and 12: Durrand Avalanche Report page 4 6.
Page 15 and 16: Durrand Avalanche Report page 8 G.
Page 21 and 22: Durrand Avalanche Report page 14 K.
Page 23: Durrand Avalanche Report page 16 2.
Page 27 and 28: Durrand Avalanche Report page 20 10
Page 29 and 30: Durrand Avalanche Report page 22 (h
Page 33 and 34: Durrand Avalanche Report page 26 X.
Page 39 and 40: Durrand Avalanche Report page 32 Re
Page 41 and 42: Durrand Avalanche Report page 34 Re

Analysis of the Durrand Glacier Avalanche Accident

Create successful ePaper yourself

Delete template?

Save as template?