Measuring spatial variations of weak layer and slab properties with regard to snow slope stability

Bellaire, Sascha; Schweizer, Jürg

doi:10.1016/j.coldregions.2010.08.013

Cited by 25 publications

(43 citation statements)

References 21 publications

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“…They pointed out the importance of signal quality control and showed the improvement in classification accuracy that can be obtained when several SMP measurements within an area of a few m 2 are performed. Lutz et al (2009) and Bellaire and Schweizer (2011) also found the micro-structural strength of the weak layer to be related to stability. Floyer and Jamieson (2009) predicted the fracture character of compression tests (CT) from adjacent SABRE penetrometer profiles (Mackenzie and Payten, 2002), whereas van Herwijnen et al (2009) found snow stratigraphy derived from microstructural properties of the SMP to be related to the fracture type in CTs.…”

Section: Introductionmentioning

confidence: 99%

“…However, relating spatial variations as derived from point measurements to slope stability has so far not been successful. For example, Bellaire and Schweizer (2011) stated that firm conclusions on the dependence of slope stability on spatial variations were not possible due to the limited range of snow conditions in the data set and the fact that the definition of slope stability is partly intangible. From a theoretical point of view, as supported by numerical modeling (e.g., Fyffe and Zaiser, 2004;Gaume et al, 2014;Kronholm and Birkeland, 2005), it seems clear that stability variations at the slope scale can either promote or hinder slope failure.…”

Section: Introductionmentioning

confidence: 99%

“…We will present a first attempt to directly derive an index of snow stability from the SMP signal and compare it to results of numerous small-scale stability tests (CT). The index will then be applied to the gridded SMP measurements collected on 11 slopes by Bellaire and Schweizer (2011) to explore the spatial structure of stability on these slopes and possibly relate it to slope stability. The index will at best be an estimate of the probability of initiating a failure in a weak layer, but it will not provide any information on the propensity of crack propagation.…”

Section: Introductionmentioning

confidence: 99%

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

Schweizer¹,

Reuter²

2015

Nat. Hazards Earth Syst. Sci.

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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.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Schweizer¹,

Reuter²

2015

Nat. Hazards Earth Syst. Sci.

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“…The investigation into the spatial variability of snow ablation was performed in an Alpine catchment, located in the Wannengrat area (Fig. 1b), where several studies on snow depth variability, snowpack stability and snow-hydrology have been completed in recent years Grünewald et al, 2010;Bellaire and Schweizer, 2011;Grünewald and Lehning, 2011;Groot Zwaaftink et al, 2011;Schirmer et al, 2011; Egli et al, 2011). The elevation ranges from 1940 to 2658 m a.s.l.…”

Section: Study Sitementioning

confidence: 99%

Micrometeorological processes driving snow ablation in an Alpine catchment

Mott¹,

Egli²,

Grünewald³

et al. 2011

The Cryosphere

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Abstract. Mountain snow covers typically become patchy over the course of a melting season. The snow pattern during melt is mainly governed by the end of winter snow depth distribution and the local energy balance. The objective of this study is to investigate micro-meteorological processes driving snow ablation in an Alpine catchment. For this purpose we combine a meteorological boundary-layer model (Advanced Regional Prediction System) with a fully distributed energy balance model (Alpine3D). Turbulent fluxes above melting snow are further investigated by using data from eddy-correlation systems. We compare modeled snow ablation to measured ablation rates as obtained from a series of Terrestrial Laser Scanning campaigns covering a complete ablation season. The measured ablation rates indicate that the advection of sensible heat causes locally increased ablation rates at the upwind edges of the snow patches. The effect, however, appears to be active over rather short distances of about 4-6 m. Measurements suggest that mean wind velocities of about 5 m s −1 are required for advective heat transport to increase snow ablation over a long fetch distance of about 20 m. Neglecting this effect, the model is able to capture the mean ablation rates for early ablation periods but strongly overestimates snow ablation once the fraction of snow coverage is below a critical value of approximately 0.6. While radiation dominates snow ablation early in the season, the turbulent flux contribution becomes important late in the season. Simulation results indicate that the air temperatures appear to overestimate the local air temperature above snow patches once the snow coverage is low. Measured turbulent fluxes support these findings by suggesting a stable internal boundary layer close to the snow surface causing a strong decrease of the sensible heat flux towards the snow cover.Correspondence to: R. Mott (mott@slf.ch) Thus, the existence of a stable internal boundary layer above a patchy snow cover exerts a dominant control on the timing and magnitude of snow ablation for patchy snow covers.

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“…More recently, it was recognized that these spatial variations play an important role in the fracture processes of failure initiation and crack propagation in the weak layer leading to dry snow slab avalanche release [Schweizer et al, 2008]. However, the link between snowpack spatial variability and slope stability has still not been fully established [Bellaire and Schweizer, 2011] and is currently still a topic of active research [Reuter and Schweizer, 2013].…”

Section: Introductionmentioning

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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Measuring spatial variations of weak layer and slab properties with regard to snow slope stability

Cited by 25 publications

References 21 publications

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

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

Micrometeorological processes driving snow ablation in an Alpine catchment

Evaluation of slope stability with respect to snowpack spatial variability

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