Item: Glide avalanche forecasting
Title: Glide avalanche forecasting
Proceedings: Proceedings of the 1996 International Snow Science Workshop, Banff, Canada
Authors: A. Wilson, G. Statham, R. Bilak, B. Allen, The University of Calgary, 3Selkirk District Office, Ministry of Transportation and Highways, Revelstoke, British Columbia, Canada
Abstract: The forecasting of glide avalanches is particularly important when human life or structures are threatened. The best way to reduce the impact of such avalanches is by suitable controls. Control requires that closures are in effect during unstable periods and/or explosives are used to minimize any risks. However, gliding, and the stability of a glide slabs are not easy to predict rendering the control process a challenging task. Until recently it was thought that water had to be present for gliding to occur [McClung 1987]. However, a two year study showed that in 88% of the cases of gliding water was present at the snow ground interface; the other 12% were during cold periods [McClung 1990]. This, along with the fact that glide avalanches do not necessarily occur during storm cycles, leads to the conclusion that forecasters require more information if they are to make accurate forecasts. It is generally agreed that rapid displacement of the snow pack occurs before glide avalanches [McClung 1987]. The physical measurement of displacements in the snow pack has been attempted in the field [Akitaya 1988, In der Gand 1966, Lackinger 1986] but all of these methods can only measure one avalanche cycle. Thus, unfortunately, the technology to provide forecasters with continuous glide monitoring throughout the a glide cycle season has not as yet been developed. This paper presents a new approach which has the potential to measure snow motion throughout the winter season. The avalanche starting zone chosen was path #3.7 at Galena'Pass, British Columbia. Path 3.7 is a southeast aspect with a vertical fall to the highway of 700 meters. The instrumentation was a sprung probe which tilts as the snow moves. Once the slope has avalanched the probe returns to an upright position ready to monitor the next avalanche cycle.
Keywords: avalanche forecasting, snow gliding, avalanche release, snow pack
Digital Abstract Not Available