Coupled Snow Cover and Avalanche Dynamics Simulations to Evaluate Wet Snow Avalanche Activity

Abstract

We present physics‐based snowpack simulations for four snow seasons with detailed wet snow avalanche activity records. The distributed, spatially explicit simulations using the Alpine3D and SNOWPACK model show that the simulated snowpack in the release areas of documented wet snow avalanches often exhibits its first wetting of the season on the release day. This first wetting is accompanied in the simulations by liquid water accumulating on capillary barriers, often formed by depth hoar layers. The strongest water accumulations and largest increases in percolation depth are found on the day of avalanche release. For individual avalanche paths, however, this only holds in 25%–30% of the cases. Assuming that the depth of the strongest water accumulation corresponds to the avalanche fracture depth, the avalanche dynamics model RAMMS‐Extended was run using simulated snowpack properties as initial conditions in the release area and boundary conditions along the avalanche path. On average, the simulated affected area by the avalanche and runout distance for the release day are statistically significant in closer agreement with the observations than two days before the release. This does not hold for the simulations of 1 day before and 1 and 2 days after the release. This suggests that fracture depths and the temporal evolution of percolation depths are adequately simulated within a ±1‐day period. The results show a large potential for distributed snow cover and avalanche dynamics simulations to assess wet snow avalanche hazards, although predictions for individual avalanche paths remain challenging.

Mapping avalanches with satellites – evaluation of performance and completeness

“…for validation of the avalanche forecast, as input to model wet-snow avalanche occurrence and run-out distance, or to derive terrain characteristics describing potential release areas (e.g. Schweizer et al, 2003;Wever et al, 2018;Bühler et al, 2018;Harvey et al, 2018;. The properties of this data set make it a potential candidate to validate avalanches detected e.g.…”

Wet‐Snow Metamorphism Drives the Transition From Preferential to Matrix Flow in Snow

“…On the other hand, one‐dimensional geometries overestimate grain size when applied to conditions that are more representative of natural snow (Avanzi et al, ) than the homogeneous conditions of, for example, Colbeck (). Since 1‐D approaches are still the most popular choice for firn meltwater retention studies (e.g., Marchenko et al, ; Reijmer et al, ; Steger, Reijmer, van den Broeke, Wever, et al, ), wet‐snow avalanche assessments (Wever et al, ; Wever, Vera Valero, et al, ), and snowmelt forecasting (e.g., DeWalle & Rango, ; Markstrom et al, ; Wever et al, ), we suggest that future modeling improvements in this regard should focus on increasing model dimensionality to improve predictions of the structural evolution of wet snow (Verjans et al, ).…”

“…Water flow through snow dictates snowpack runoff generation (Hirashima et al, ; Wever et al, ), wet‐snow microstructure metamorphism (Avanzi et al, ; Brun, ), albedo evolution (Dietz et al, ), and settling (Marshall et al, ). Correctly simulating this process is thus a key toward better quantifying impacts of rain‐on‐snow events (Würzer et al, , ), wet‐snow avalanches (Baggi & Schweizer, ; Mitterer et al, ; Wever, Vera Valero, et al, ; Wever et al, ), and sea level rise (Forster et al, ; Harper et al, ; Machguth et al, ; Steger, Reijmer, van den Broeke, Wever, et al, ), all risks that are predicted to increase in a warming climate (e.g., Pielmeier et al, ; Steger, Reijmer, & Broeke, ).…”

Mass wasting susceptibility assessment of snow avalanches using machine learning models

“…The complexity of avalanche models has been discussed in many studies 27 – 31 . The snowpack, meteorology, terrain, and slope characteristics are the predominant contributing factors initiating the avalanche movement and propagation, and the debris deposition 2 , 32 , 33 . Based on the interaction of these factors, the motion and run out of snow and eventually, the avalanche formation and propagation can be modeled 2 , 32 , 34 – 36 .…”