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here to see some field pictures of this project Avalanches are one of the most deadly natural hazards in the Western United States. Physical avalanche models and geographic data advance avalanche forecasting by evaluating avalanche factors over space.. Snow avalanches occur when a portion of the snowpack becomes unstable, breaks loose, and proceeds to move rapidly down slope. Determining when and where snowpack instabilities occur will save lives, save money, and speed transportation networks. The Snow Slope Stability model (SNOSS) developed by Conway and Wilbur (1999), is a one-dimensional physical avalanche model that has been shown to work well at in the maritime snowpacks of the Northwestern, United States. This model creates a stability index by dividing the snow strength by the stress applied. When the stability index is less than one an avalanche is predicted. The SNOSS model was combined with data from geographical information systems (GIS) to create the GISSNOSS model. GISSNOSS is a user friendly, spatially distributed model of slope stability. GISSNOSS outputs an easy to read map of slope stability at each time step. The figure below show and example of the avalanche potiental maps the GISSNOSS model creates.
Figure 1 : Time evolution of GISSNOSS run 1 and run 2 at East Shed avalanche path on Snoqualmie Pass, Washington for the March 1, 1997 avalanche cycle. When the slope stability, index shown by the scale bar, is less than 1 (red colors) the slope is considered unstable and an avalanche is expected. The differences between run 1 and run 2 are caused by the difference in precipitation fields applied to the model. Small scale precipitation data is needed to constrain the model. As shown in figure 1 small scale precipitation patters, as well as, small scale temperature patterns are important when modeling avalanches on small scales using GISSNOSS. A problem arises that field data on precipitation and temperature is not available on small scales. Data is expensive to monitor on small scales. This projects investigates the use of small, inexpensive and rugged micro sensors that can be used in avalanche prone areas. We are investigating the the use of Ibutton temperature sensors and Ping depths sensors to gather temperature and snow depth measurements, respectively, at multiple locations on an avalanche path. Steven Domonokos, University of Washington Department of Atmospheric Sciences, designed and built temperature encloses for the ibuttons that were deployed first in the winter of 2006.
Figure 2: The ibutton sensor and temperature enclosure The ibutton temperature sensors have proven to be a good, reliable method for taking temperature measurements. During the 2007 field seasons the ping sensors will be evaluated for their abilities to determine snow depth. Some References Conway, H. and W. Carran. (in press), Forecasting direct-action avalanches during storms. Marshall, H.P., H. Conway and L.A. Rasmussen (1999). Snow desification during rain. Cold Regions Science and Technology 30, 35-41. McClung, D. and P. Schaerer (1993), The Avalanche Handbook. The Mountaineers, Seattle. Northwest Avalanche Center (NWAC) (2005), Washington Fatality by Natural Hazard.http://www.nwac.noaa.gov/accidents.htm. Acessed June 1, 2005. Perla, R.I. (1980) Dynamics of Snow and Ice Masses CH 7 Avalanche Release, Motion and Impact. Pages 397-462.
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