Item: Bridal veil falls avalanche 1996
Title: Bridal veil falls avalanche 1996
Proceedings: Proceedings of the 1996 International Snow Science Workshop, Banff, Canada
Authors: Kevin Griffith, Utah Department of Transportation, Region Three Avalanche Forecaster, P.O. Box 993, Park City, Utah 84060 USA
Abstract: Bridal Veil Falls avalanche path released January 31, 1996.The resulting avalanche ran down to and across the floor of Provo Canyon. It continued up the opposite side of the canyon, crossed US Highway 189 and destroyed the power lines beyond the highway. It also blew two railroad cars about fifty meters and severely damaged the base terminal of the four passenger tram. This was part of a much larger avalanche that included two more drainages south of Bridal Veil. Located in the Wasatch Mountains of Utah, Provo Canyon is at 400 21' north latitude, 1110 36' west longitude. Provo Canyon has the three largest slidepaths that threaten a highway in the state of Utah. They are Bridal Veil Falls, Lost Creek, and Slide Canyon. The starting zone and track of Bridal Veil have an area of approximately 160 hectares and a vertical drop of 1626 meters. An interesting feature of the track is a cliff just above the runout zone. About 120 meters in height, the cliff has a perennial waterfall that the slidepath is named after. The storm cycle that produced the Bridal Veil Falls avalanche began January 16, and by the 31st had dropped 239 centimeters of snow (H20 equivalent 181 millimeters) on the Utah Department of Transportation (UDOT) snow study plot at Aspen Grove (see precipitation table). Total snow depth at Aspen Grove (elevation 2100 meters) was 18 centimeters on January 16 and 122 centimeters on the 31st. The ten days before the storm cycle was clear with no precipitation. Before the storm cycle the snowpack was 76 centimeters deep at the Sundance study plot at 2438 meters, and was weak recrystallized snow. On January 31 the total depth at the Sundance study plot was 254 centimeters. UDOT did avalanche control (with positive results) on the north side of Provo Canyon on the 18th and the 28th. Avalanche control work by UDOT on February 1 triggered avalanche in Slide Canyon that ran to within about runety meters ofUS 189. Slide Canyon drains into Provo canyon from the north, about two kilometers northeast of Bridal Veil Falls (see map). UDOT does not do avalanche control in any of the avalanche paths on the south Side ofProvo Canyon with the exception of the Deer Creek Dam Chute.
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Keywords: airblast, crown face, dry slab avalanche, highway, slidepath
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