The Landslide Blog is written by Dave Petley, who is widely recognized as a world leader in the study and management of landslides.
On Sunday 30 July 2023 a large rock slope collapse occurred close in the area of the village of Bisisthal in Switzerland. The collapse occurred in the Gwalpeten area in two phases, consisting of an initial fall of about 150,000 cubic metres, followed by a second collapse of about 300,000 cubic metres.
The failure occurred in an area that was known to be unstable and that was being monitored. Increased rates of movement had been noted in recent weeks.
There are some videos of the collapses on Youtube. There was a webcam mounted at the top of the slope, monitoring the rock pillar:-
Whilst an even better video was collected from within the valley. This video is worth a wait – the initial small event is not the main collapse:
This video beautifully captures the initial multiple collapses of the rock slope and the transition to a rock avalanche:-
There are other videos too – a Swiss news report presents a medley of them.
The location of the landslide near to Bisisthal is [46.8933, 8.8614]. At the time of writing there has been too much cloud since the collapse to allow the acquisition of good satellite images of the aftermath.
The rock avalanche occurred in an area of talus and mountain pasture, so there was no loss of life and no damage to key buildings or infrastructure, and the cattle that graze the area had been moved to a safe place. There is an interesting article on the website of Innet Monitoing AG about the work that it undertook at the site. Further rockfalls are possible.
Many thanks to Mauro Häusler for tipping me off about this major event.