The population of Brienz in the Swiss canton of Graubunden were briefly allowed to return to the town this week after being evacuated on 12 May 2023, reported SRF.
Two 90-minute time slots were planned on Wednesday with limits of 30 people at a time, reported the broadcaster.
The visits were aimed at enabling the residents to get important things or personal items from their houses. Farmers were allowed back on Tuesday to cut grass and process it into hay or silage.
The town is exposed to a high risk of rock slides. Predicting exactly what will happen and when is difficult, but the risks were too high to leave people in the town.
For several years the risk was limited to rolling boulders. A sensor and traffic lights halting traffic on the road in and out of town were enough to keep residents safe. But more recently the nearby hillside has become more unstable. Rockfalls, a steady, sluggish flow of debris, or a large rockslide are all possibilities now.
A year ago the village itself was moving down the valley at a rate of 1.5 metres a year. But the steep slope behind the town was moving at 7-8 metres a year. The pace of movement has been accelerating rapidly recently. Geologist Stefan Schneider says something in the geological sub surface flipped like a switch. He is not sure why. But it may be related to heavy winter avalanches in 1999.
On 12 May 2023, the risks reached the point where it was too dangerous for residents to remain. A video by the BBC on the subject can be viewed here.
The YouTube channel GeologyHub (see video above) explains how an island of rock risks breaking away and falling rapidly, destroying the town of Brienz and how a previous rockslide occurred nearby in 1878. Rising temperatures are affecting the geology of the region, generating geological instability.
How and when the rock will fall and how much damage will occur to the town is hard to predict. Only time will tell.
SRF article (in German)