Item: Rapid Assessment of a Large-Magnitude Snow Avalanche Event in Colorado
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Title: Rapid Assessment of a Large-Magnitude Snow Avalanche Event in Colorado
Proceedings: Proceedings, 2012 International Snow Science Workshop, Anchorage, Alaska
Authors:
- Sara E. Simonson [ Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, CO 80523 ] [ Earth Sciences Watershed Program, Colorado State University, Fort Collins, CO 80523 ]
- Scott Toepfer [ Colorado Avalanche Information Center, Boulder, CO 80305 ]
- Ethan M. Greene [ Colorado Avalanche Information Center, Boulder, CO 80305 ]
- Steven R. Fassnacht [ Earth Sciences Watershed Program, Colorado State University, Fort Collins, CO 80523 ]
- Thomas J. Stohlgren [ U.S. Geological Survey, Fort Collins Science Center, Fort Collins, CO 80526 ]
- Hal Hartman [ Hal Hartman, SPH Works, LLC , CO 81654 ]
Date: 2012
Abstract: The winter of 2010-2011 set records for snowfall and snowpack depth for many mountain areas in Colorado. Large, destructive avalanches were reported from locations across the state. On April 29, 2011, an impressive slide damaged high voltage power lines along Peru Creek, near Montezuma, CO. The avalanche destroyed a power line tower that had been in place since the 1970s, and deposited massive piles of snow, rocks, and woody debris in the runout zone. The slide created fresh trimlines, widening the existing avalanche path by uprooting, stripping, and breaking trees. The disturbance event left behind many mature downed trees and extensive areas of vegetation damage, providing a unique opportunity to improve our knowledge of local avalanche frequency and magnitude. Initially, we gathered historical records of avalanche incidents and observations, and used repeat photography to track changes in the avalanche path vegetation over time. Next, we used field measurements to survey the vegetation damage, assess relative tree ages, and estimate maximum runout distances. We collected discs and cores from downed trees to detect past avalanche impacts recorded in woody plant tissue. Initial cross section samples from the downed trees avalanche signals included direct impact scars and development of reaction wood in response to tilting. To provide insight on the avalanche dynamics, we used terrain features and local snowpack observations as inputs in a one-dimensional model to estimate the avalanche velocity, height of flowing snow, impact pressures, and mass of the debris. For Colorado, and perhaps elsewhere, we conclude that several vegetation ecology approaches can be used to characterize local avalanche frequency and magnitude.
Object ID: issw-2012-666-673.pdf
Language of Article: English
Presenter(s): unknown
Keywords: large-magnitude avalanche, avalanche path vegetation, tree-ring analyses, disturbance assessment
Page Number(s): 666-673
Subjects: avalanche damage vegetation historical avalanche data
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