Articles | Volume 15, issue 1
Nat. Hazards Earth Syst. Sci., 15, 109–118, 2015
Nat. Hazards Earth Syst. Sci., 15, 109–118, 2015

Research article 13 Jan 2015

Research article | 13 Jan 2015

A new index combining weak layer and slab properties for snow instability prediction

J. Schweizer and B. Reuter J. Schweizer and B. Reuter
  • WSL Institute for Snow and Avalanche Research SLF, Flüelastrasse 11, 7260 Davos Dorf, Switzerland

Abstract. Snow slope stability evaluation requires considering weak layer as well as slab properties – and in particular their interaction. We developed a stability index from snow micro-penetrometer (SMP) measurements and compared it to 129 concurrent point observations with the compression test (CT). The index considers the SMP-derived micro-structural strength and the additional load, which depends on the hardness of the surface layers. The new quantitative measure of stability discriminated well between point observations rated as either "poor" or "fair" (CT < 19) and those rated as "good" (CT ≥ 19). However, discrimination power within the intermediate range was low. We then applied the index to gridded snow micro-penetrometer measurements from 11 snow slopes to explore the spatial structure and possibly relate it to slope stability. Stability index distributions on the 11 slopes reflected various possible strength and load (stress) distributions that can naturally occur. Their relation to slope stability was poor, possibly because the index does not consider crack propagation. Hence, the relation between spatial patterns of point stability and slope stability remains elusive. Whereas this is the first attempt of a truly quantitative measure of stability, future developments should consider a better reference of stability and incorporate a measure of crack propagation.

Final-revised paper