Item: Sawlem: slab and weak layer evolution model
Title: Sawlem: slab and weak layer evolution model
Proceedings: Proceedings of the 2006 International Snow Science Workshop, Telluride, Colorado
Authors: Antonia Zeidler, Bruce Jamieson, Thomas Chalmers, Greg Johnson, Integrated Environmental Consultants Namibia, Windhoek, Namibia, Dept. of Civil Engineering / Dept. of Geology and Geophysics, University of Calgary, Golden, BC, Canadian Avalanche Cente
Abstract: Snowpack evolution models developed in Europe require meteorological and radiation instrumentation rarely used in North America. In contrast, SAWLEM uses a spreadsheet to model the evolution of persistent weak layers and the overlying dry slabs using weekly manual snow profiles in a study plot and daily measurements or long-term average values of snowfall. The shear strength of a persistent weak layer, dependent on the grain type, is estimated based on parameters such as slab load, grain size, thickness of the weak layer, thickness of the slab, snowpack height and temperature just below the weak layer from a detailed manual profile in a study plot. The calculated shear strength is adjusted daily based on the most recently measured snow profile parameters and recent snowfall rates or average long-term snowfall values in the area according to previously published empirical models. Slab load, ski penetration and skier stress at the base of the slab and subsequently skier stability indices based on the ratio of shear strength to shear stress such as Sk38 are calculated. For daily calculations of Sk38 the slab settles according to the long-term average and the 24 hour snowfall is added to the slab thickness in order to calculate the slab load on days without snowprofile observations. We summarize comparisons of the estimated and measured shear strength as well as correlations of Sk38 with skier triggered avalanche activity in the Columbia Mountains.
Keywords: slab avalanches, avalanche forecasting, snowpack stratigraphy, persistent weak layers
Digital Abstract Not Available