Major rock slope collapse in Bisisthal, Switzerland

A major rock slope collapse occurred near the village of Bisisthal in Switzerland on July 30, 2023. The collapse, which occurred in the Gwalpeten area, consisted of two phases totaling 450 000 m³ (15.8 million ft³) of rock, in a location that had been under scrutiny due to known instability.

The large rockfall, reported to have occurred in two distinct phases, was documented in the vicinity of the village of Bisisthal in Switzerland. The first wave of the landslide swept away about 150 000 m³ (5.3 million ft³) of rock, while a second, more impactful, wave dislodged approximately 300 000 m³ (10.6 million ft³).

The site of the landslide, located near Bisisthal, is an area known for its instability and has been under careful monitoring. Dr. Dave Petley of The Landslides Blog explained, “Increased rates of movement had been noted in recent weeks.” This early detection of heightened activity likely played a significant role in preventing any loss of life or damage to essential buildings or infrastructure.

Due to the event’s occurrence in an area characterized by talus and mountain pasture, no injuries or fatalities were reported. Furthermore, no damage was inflicted upon critical buildings or infrastructure, as the zone is largely unpopulated and devoid of such constructs.

The local cattle population, often seen grazing in the region, was relocated to a secure location before the landslide. This strategic relocation played a pivotal role in ensuring the safety of the cattle and mitigating potential economic losses.

At present, the post-event evaluation of the area is ongoing. Unfortunately, weather conditions have posed a challenge, as persistent cloud cover has inhibited the acquisition of high-quality satellite images for further study. Dr. Petley further warned that the site remains vulnerable to potential rockfalls.

Innet Monitoring AG, a renowned entity in the domain of monitoring geological activities, had undertaken notable work at the site. The significant landslide, while unfortunate, provided crucial data and observations that can aid in better understanding and managing such geological occurrences in the future.

References:

¹ Bisisthal: a one million tonne rock slope collapse in Switzerland – The Landslide Blog – August 2, 2023

Featured image credit: gerzgl (stillshot)