Talus buttressing controlled the final creep phase of a rockslide, threatening the village Brienz/Brinzauls, Switzerland

In this study, we present indicators suggesting a significant influence of a talus buttress on the displacement velocities of a rockslide during its tertiary creep phase. The event analyzed is the collapse of the’Insel’ compartment of the Brienz/Brinzauls landslide complex in 2023. This rockslide entered the tertiary creep phase after its toppling foot failed and began to slide. The subsequent acceleration was characterized by exponential phases alternating with returns to a linear velocity increase. This behavior deviated significantly from the predictions of the applied creep model. No external influences could be identified to explain these deviations. At its eastern foot, the rockslide was buttressed by a talus slope. We analyzed the displacements of the talus and found clear indications of a compressional regime, including the formation of sequential thrusts. During thrusting, the overall resistive strength of the talus buttress fluctuates depending on the activity cycles of individual thrusts. Thus, the talus buttress was an effective limiting and disturbing factor for the acceleration of the rockslide. Additionally, it caused internal shear stress in the rockslide, ultimately leading to the decoupling of its buttressed eastern part and the subsequent collapse of the remaining instability. This significant influence of the talus buttress on the failure process highlights the importance of considering talus mechanics in comparable slope instabilities.