Piz Scerscen
(Hero photo: copyright SLF)
The Scerscen avalanche event exhibits several hallmark features of a rock-ice avalanche, beginning with the release of a mixed mass of rock and glacial ice. The avalanche initiated on a snow-covered glacier surface, immediately entraining significant quantities of additional snow and ice. This added mass and energy to the flow, which reached high initial velocities as it accelerated down the steep initial slope.
The soil resistance is calculated with an upper bound solution. The approach is based on a bearing capacity problem of a strip foundation. The soil is homogeneous, isotropic, with a Mohr Coulomb plasticity model and associated flow rule $(\Psi=\phi)$.
As the avalanche moved onto a flatter section of terrain, it experienced a natural loss of momentum. However, upon encountering a steep ice cliff, the flow reaccelerated dramatically. During this phase, it aggressively scoured the glacier face, entraining a massive volume of ice and further amplifying the complexity and energy of the system.
Figure 1: Simulated flow velocities of the Scerscen rock-ice avalanche. The model shows high velocities immediately after release, driven by the steep initial slope and the combined rock–ice mass. A second acceleration phase occurs as the avalanche descends a glaciated cliff, entraining large volumes of snow and glacier ice, which increases the flow’s volume, reduces internal friction, and contributes to its long runout.
The combination of frictional heating and the mechanical disruption of snow and ice led to substantial meltwater production within the flow. As water content increased, the avalanche underwent a critical transition—from a regime dominated by capillary forces to one increasingly influenced by internal pore-water pressure. This evolution significantly reduced internal friction, ultimately resulting in an exceptionally long runout.
The RAMMS::RockIce simulation successfully captured both the physical extent of the powder cloud and the critical internal transition of the avalanche. The model accurately reproduced the transformation from a relatively dry rock-ice flow into a highly mobile, fluidized avalanche governed by pore-pressure dynamics – demonstrating the predictive power of RAMMS in simulating complex, multiphase mass movement events.
Figure 2: Modeled deposition pattern of the Scerscen rock-ice avalanche, highlighting its distinctive flow behavior. A substantial portion of the avalanche mass traversed the steep terrain and ultimately reached the valley floor, reflecting the high mobility of the event and the influence of meltwater-driven flow transformation.
Video 1: Simulated evolution of the Piz Scerscen rock-ice avalanche.
The RAMMS::RockIce simulation reveals that the Piz Scerscen avalanche unfolded in two distinct phases. Immediately following release, the avalanche surged downslope at extreme speeds – reaching peak velocities of up to 75 m/s – before impacting the glacier front. This initial phase was characterized by rapid motion and significant entrainment of glacial material. In the second phase, the flow gradually decelerated, eventually coming to rest as momentum was lost. Final deposit depths exceeded 20 meters in some areas (highlighted in red), consisting of a complex mixture: approximately 40 percent rock, 35 percent ice, and 25 percent soil and snow. This composition underscores the highly dynamic and multi-material nature of high-mountain avalanche events.
Video 2: Modeling entrainment processes in RAMMS::RockIce – Piz Scerscen case study.
To realistically simulate entrainment during the Piz Scerscen rock-ice avalanche, four distinct entrainment zones were defined within the RAMMS::RockIce model:
- a dense, early-spring snowpack,
- the compact and stable upper glacier,
- the fractured and unstable glacier front, and
- unconsolidated sediment deposits beneath the glacier.
This video visualizes the progressive removal of surface material across these zones. The erosion of the snowpack is shown by height reductions from positive values down to zero, while deeper entrainment—such as glacier ice and subglacial sediments—is represented by changes from zero to negative heights. Together, these processes demonstrate the powerful capacity of mixed avalanches to reshape the landscape through mass removal and material incorporation.
