Evaluating and improving the stability predictions of the snow cover model SNOWPACK

Schweizer, Jürg; Bellaire, Sascha; Fierz, Charles; Lehning, Michael; Pielmeier, Christine

doi:10.1016/j.coldregions.2006.05.007

Cited by 60 publications

(50 citation statements)

References 20 publications

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“…The 1-D snow cover model SNOWPACK (Bartelt and Lehning, 2002;Lehning et al, 2002a, b) was developed for this purpose and in addition to the snow cover stratigraphy provides information on snow stability (Lehning et al, 2004;Monti et al, 2014a;Schweizer et al, 2006). As the SK 38 is already calculated within SNOWPACK (Lehning et al, 2004), the proposed approach for the additional skier stress within a multilayered snowpack can easily be implemented.…”

Section: Applicability Of the Sk ML 38 To The 1-d Snow Cover Model Snmentioning

confidence: 99%

Snow instability evaluation: calculating the skier-induced stress in a multi-layered snowpack

Monti¹,

Gaume²,

Herwijnen³

et al. 2016

Nat. Hazards Earth Syst. Sci.

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Abstract. The process of dry-snow slab avalanche formation can be divided into two phases: failure initiation and crack propagation. Several approaches tried to quantify slab avalanche release probability in terms of failure initiation based on shear stress and strength. Though it is known that both the properties of the weak layer and the slab play a major role in avalanche release, most previous approaches only considered slab properties in terms of slab depth, average density and skier penetration. For example, for the skier stability index, the additional stress (e.g. due to a skier) at the depth of the weak layer is calculated by assuming that the snow cover can be considered a semi-infinite, elastic, half-space. We suggest a new approach based on a simplification of the multi-layered elasticity theory in order to easily compute the additional stress due to a skier at the depth of the weak layer, taking into account the layering of the snow slab and the substratum. We first tested the proposed approach on simplified snow profiles, then on manually observed snow profiles including a stability test and, finally, on simulated snow profiles. Our simple approach reproduced the additional stress obtained by finite element simulations for the simplified profiles well -except that the sequence of layering in the slab cannot be replicated. Once implemented into the classical skier stability index and applied to manually observed snow profiles classified into different stability classes, the classification accuracy improved with the new approach. Finally, we implemented the refined skier stability index into the 1-D snow cover model SNOWPACK. The two study cases presented in this paper showed promising results even though further verification is still needed. In the future, we intend to implement the proposed approach for describing skier-induced stress within a multi-layered snowpack into more complex models which take into account not only failure initiation but also crack propagation.

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Section: Applicability Of the Sk ML 38 To The 1-d Snow Cover Model Snmentioning

confidence: 99%

Snow instability evaluation: calculating the skier-induced stress in a multi-layered snowpack

Monti¹,

Gaume²,

Herwijnen³

et al. 2016

Nat. Hazards Earth Syst. Sci.

Self Cite

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“…In order to illustrate the knock-down effect and its importance for avalanche formation and forecasting, we compare the classical stability index, which is widely used for avalanche forecasting (in SAFRAN-Crocus-MEPRA in France [Brun et al, 1992;Giraud, 1992] and in SNOWPACK in Switzerland [Lehning et al, 2004;Schweizer et al, 2006]), with our modeled avalanche probability for the simple case of a virtual snow slope (Figure 6). The slope has a maximum angle of 45…”

Section: Illustration Of the Knock-down Effectmentioning

confidence: 99%

Evaluation of slope stability with respect to snowpack spatial variability

Gaume¹,

Schweizer²,

Herwijnen³

et al. 2014

JGR Earth Surface

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The evaluation of avalanche release conditions constitutes a great challenge for risk assessment in mountainous areas. The spatial variability of snowpack properties has an important impact on snow slope stability and thus on avalanche formation, since it strongly influences failure initiation and crack propagation in weak snow layers. Hence, the determination of the link between these spatial variations and slope stability is very important, in particular, for avalanche public forecasting. In this study, a statistical-mechanical model of the slab-weak layer (WL) system relying on stochastic finite element simulations is used to investigate snowpack stability and avalanche release probability for spontaneously releasing avalanches. This model accounts, in particular, for the spatial variations of WL shear strength and stress redistribution by elasticity of the slab. We show how avalanche release probability can be computed from release depth distributions, which allows us to study the influence of WL spatial variations and slab properties on slope stability. The importance of smoothing effects by slab elasticity is verified and the crucial impact of spatial variation characteristics on the so-called knock-down effect on slope stability is revisited using this model. Finally, critical length values are computed from the simulations as a function of the various model parameters and are compared to field data obtained with propagation saw tests.

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“…During the past decades, theoretical and experimental studies have gradually enhanced the knowledge of the fracture process in snow, allowing a better estimation of snowpack stability (McClung, 1979;Jamieson and Johnston, 1990;Föhn et al, 1998;Johnston, 1998, 2001;Schweizer et al, 2006;Sigrist and Schweizer, 2007). Despite these advances, the limited understanding of crack propagation and fracture arrest propensity still limits the evaluation of the avalanche size and thus impedes avalanche forecasting and hazard mapping.…”

Section: Introductionmentioning

confidence: 99%

Influence of weak layer heterogeneity and slab properties on slab tensile failure propensity and avalanche release area

Gaume¹,

Chambon

Eckert

et al. 2015

The Cryosphere

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Abstract. Dry-snow slab avalanches are generally caused by a sequence of fracture processes, including failure initiation in a weak snow layer underlying a cohesive slab followed by crack propagation within the weak layer (WL) and tensile fracture through the slab. During past decades, theoretical and experimental work has gradually increased our knowledge of the fracture process in snow. However, our limited understanding of crack propagation and fracture arrest propensity prevents the evaluation of avalanche release sizes and thus impedes hazard assessment. To address this issue, slab tensile failure propensity is examined using a mechanically based statistical model of the slab-WL system based on the finite element method. This model accounts for WL heterogeneity, stress redistribution by slab elasticity and possible tensile failure of the slab. Two types of avalanche release are distinguished in the simulations: (1) full-slope release if the heterogeneity is not sufficient to stop crack propagation and trigger a tensile failure within the slab; (2) partial-slope release if fracture arrest and slab tensile failure occur due to the WL heterogeneity. The probability of these two release types is presented as a function of the characteristics of WL heterogeneity and the slab. One of the main outcomes is that, for realistic values of the parameters, the tensile failure propensity is mainly influenced by slab properties. Hard and thick snow slabs are more prone to wide-scale crack propagation and thus lead to larger avalanches (full-slope release). In this case, the avalanche size is mainly influenced by topographical and morphological features such as rocks, trees, slope curvature and the spatial variability of the snow depth as often claimed in the literature.

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Evaluating and improving the stability predictions of the snow cover model SNOWPACK

Cited by 60 publications

References 20 publications

Snow instability evaluation: calculating the skier-induced stress in a multi-layered snowpack

Snow instability evaluation: calculating the skier-induced stress in a multi-layered snowpack

Evaluation of slope stability with respect to snowpack spatial variability

Influence of weak layer heterogeneity and slab properties on slab tensile failure propensity and avalanche release area

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