Author(s):
Kathy Hansen - Montana State University
Birkeland, K. - Montana State University and USDA Forest Service National Avalanche Center, Bozeman, Montana
Kalle Kronholm - Montana State University
Eric Lutz - Montana State University
Spencer Logan - Montana State University and Colorado Avalanche Information Center, Boulder
Abstract:
Snow stability varies across slopes and changes through time. These variations can result in the potential for avalanches being triggered from one point on a slope, while other parts can be safely traversed. Avalanches may occur today but not tomorrow. In order to better forecast avalanches, we are studying where, when, and why this occurs. Our approach is unique by using intesive field samplling with standard methods and the high-resolution SwissMicroPen, signal-analyses techniques, and a cellular automaton model. The field areas are within the Madison and Bridger Ranges of southwestern Montana. We suggest that variations in the stability are non-linear and dynamic. As a snowpack stabilizes there should be an increase in variability, decreasing the likelihood of fracture propagation. Precise locations of weak layers from the SwissMicroPen data have been identified by using moving-window regression analyses. Shear frame test data, analyzed geostatistically, showed little spatial structure. Fracture initiation and propagation has been mimicked using our shear strength data with a cellular automaton. Results from our study are being shared with students, snow professionals, avalanche forecasters, and the public.
