An expert report shows that two houses in Lauenen are potentially at risk from a boulder that could break loose. As a protective measure, a rock underpinning will be carried out next spring.

At the end of September 2020, when a farmer was herding his cows along the Wolfegg road, a rock came loose in the steep terrain above the road. It fell onto the road and knocked off a cow’s horn. Alarmed by this incident, an initial inspection was carried out on 1 October of the same year with the district forester and the Cantonal Office for Forests and Natural Hazards.

It turned out that there were other loose rocks in the steep terrain where the stone had come from. And not only that: “By chance, during this inspection, we became aware of a boulder a little further away that poses a much greater danger,” explained municipal councilor Andreas Reichenbach.

The boulder has a visible length of about four metres, a width of two and a height of one and a half metres. “However, we don’t know how deep this boulder still reaches into the ground,” Reichenbach said. A second inspection with a geologist took place on 10 August 2021.

Simulation reveals threat
A three-dimensional rockfall simulation showed that two residential buildings on Wolfeggstrasse and Lauenenseestrasse could be in the danger zone if the boulder comes down. In order to secure the boulder, the project partner Emch+Berger AG Bern proposes to fix it by means of a concrete underpinning, which itelfs will be fastened to the ground by four anchoring bolts. Reichenbach emphasises that the planned work is a prophylactic measure and that the boulder is currently stuck. There is no acute danger.

These measures will cost around CHF 62,800 and are to be subsidised by the canton. According to the Lauenen municipal administration, a corresponding application has already been submitted, but the decision is still pending.

Further measures
But back to the rockfall that hit a cow in the first place. According to Reichenbach, this area also needs securing. Protective measures such as reforestation, a h ig h-per for ma nce catch fence, and a maintenance concept shall protect the access road and the residential building at Wolfeggstrasse 4 in the future. The corresponding costs are estimated at just under CHF 7,000.

BASED ON AVS/KEREM S MAURER