Quantification of basal friction for glide-snow avalanche mitigation measures in forested and non-forested terrain

T. Feistl, P. Bebi, L. Dreier, M. Hanewinkel, P. Bartelt
2014 NHESSD  
A long-standing problem in avalanche engineering is to design defense structures and manage forest stands such that they can withstand the forces of the natural snow cover. In this way glide-snow avalanches can be prevented. Ground friction plays a crucial role in this process. To verify existing guidelines, we collected data on the vegetation cover and terrain characteristics of 101 glide-snow release areas in Davos, Switzerland. We quantified the Coulomb friction parameter μ by applying a
more » ... μ by applying a physical model that accounts for the dynamic forces of the moving snow on the stauchzone. We investigated the role of glide length, slope steepness and friction on avalanche release. Our calculations revealed that the slope angle and slab length for smooth slopes corresponds to the technical guidelines for defense structure distances in Switzerland. Artificial defense structures, built in accordance with guidelines, prevent glide-snow avalanche releases, even when the terrain is smooth. Slopes over 40 m length and 45° steepness require a ground friction of μ = 0.7 corresponding to stumps or tree regeneration to assure protection. Forest management guidelines which define maximum forest gap sizes to prevent glide-snow avalanche release neglect the role of surface roughness and therefore underestimate the danger on smooth slopes.
doi:10.5194/nhessd-2-2947-2014 fatcat:qef6eucd2rdf3dutiteqhiif4m