Item: The broken river avalanche of august 1992; craigieburn range, new zealand
Title: The broken river avalanche of august 1992; craigieburn range, new zealand
Proceedings: Proceedings of the 1992 International Snow Science Workshop, Breckenridge, Colorado, USA
Authors: Dr. Ian Owens, Department of Geography, University of Canterbury, Private Bag, Christchurch, New Zealand, Peter Weir, Snow Avalanche Programs, Ministry of Transportation & Highways, Victoria, BC, Canada
Abstract: The Broken River avalanche resulted from a combination of factors typical of New Zealand weather conditions, especially in the intermontane areas - cold enough to develop depth hoar but maritime enough to allow rainfall to high elevations in midwinter. It occurred in one of several ski basins located above timberline in south-east facing former cirques. An overview of the starting zone shows that snow over almost the entire basin failed. The initial release was on the steeper shady aspects followed by propagation towards the sunny aspects, Approximately 40,000 t was involved. Avalanche speeds were relatively slow and most snow remained within the cirque basin deposited in depths up to 30 m. About one quarter of the debris flowed over the lip such that the total length of run-out was 1.2 km. The avalanche occurred at 1300 hr on a clear day. While the skifield was open, only the Rugby Tow was operating. Three people were clearing the rope on the Main Tow when the avalanche occurred. Two near the top clung to the rope while the avalanche moved out from under them but one person lower down was swept away and has not yet been recovered. A groomer working near the Rugby Tow was engulfed by the avalanche and may have been the trigger. Approximately 60 people were on the field; fortunately most were in Palmer Lodge when the avalanche occurred.
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Keywords: starting zone, triggering, wind speed, precipiation
Digital Abstract Not Available