Rockslide at the Ankenbälli

Around the Lower Grindelwald glacier rockslides, rockfalls, debris flows and landslides have occurred in recent years. They were caused on the one hand by the strong glacier retreat and on the other hand the thawing of the permafrost in the higher areas. Permafrost (permanently frozen soil) is ground material such as rocks or debris, frozen due to temperatures below 0 °C at least for one year. This has a stabilizing effect on rock and debris in the high mountains. When the ice melts, the mountain begins to crumble and rockslides occur. In addition, the thawing loose material is transported down to the valley during heavy rainfall events in the form of eroding debris flows. 
Block and rock slides in the Ankenbälli area, which are due to thawing of permafrost, were deposited at its bottom and at the end of the debris flow cone above the Stieregg. This led in 2000 to the redirection of the river from the Ankenbälli at the beginning of the debris flow cone. It started to deepen towards southeast, particularly due to debris flows. In this way a new trench emerged further south alongside the existing trench in the Stieregg. The eroded debris mass was estimated to be around 700.000 m3 between 2000 and 2005. Since the period of rockslide and debris flow activities, the use of the mountain trail to the Schreckhorn hut, which crosses the trench behind the Bäregg, got almost impossible. The path has to be reinstated continuously.