Glide-snow avalanches: insights from combining field monitoring, time-lapse photography and SNOWPACK simulations

Glide-snow avalanches release due to a loss of friction at the snow-soil interface, which can result in large avalanches that endanger infrastructure in alpine regions. It is hypothesized that glide-snow avalanche release is linked to the presence of liquid water at the snow-soil interface, but the driving physical processes are poorly understood and prediction remains difficult. To better understand these driving physical processes, we monitored soil (water content, matric potential, temperature) and snow properties (water content, temperature, weekly snow profiles) across a small slope (40 m x 70 m) at the Dorfberg field site above Davos, Switzerland for the winter seasons 2021/22 and 2022/23. These observations were supplemented with SNOWPACK simulations for 10 release zones across Dorfberg. In addition, SNOWPACK simulations were used to supplement a dataset of more than 900 glide-snow avalanches that were previously (seasons 2009-2023) recorded on Dorfberg using time-lapse photography. Analyses of both SNOWPACK and monitoring data show high spatial variability of soil and snow properties across the monitored slope and across Dorfberg. Spatial variability in soil water content across the monitoring slope was higher during early winter than during spring when melt-freeze cycles and subsequent water infiltration in the soil cause a spatial homogenization. Transferring findings from the field monitoring to the large dataset allowed for the identification of several temporal patterns. For example, we see a positive correlation between mean snowpack density and the number of melt-freeze cycles prior to avalanche release in spring. We see a similar correlation with snow height. Overall, our measurements show that on Dorfberg several diurnal melt-freeze cycles are necessary before glide-snow avalanche release in spring.