Rockfall alarm system in Vissoie, Val d’Anniviers

Summary

Abstract

The Val d’Anniviers is one of the major valleys of the canton of Valais in Switzerland. Well known for its winter sports opportunities and for the villages of Grimentz and Zinal, the valley is accessible by a vertiginous road exposed to a wide range of gravitational hazards. Though the Route d’Anniviers is protected by multiple galleries, severe events can still impact the road. In March 2024, a series of rockfall led to heavy accumulation of debris atop a road gallery at the entrance of the valley. A week later, on the 29th of March, bigger blocks hit the road and perforated the gallery. To avoid complete isolation, an alternative route was opened from the other side of the valley. An alarm system needed to be installed to increase the safety of workers during the gallery renovation as well as part of a long-term mitigation plan. Geoprevent was mandated on the 10th of April by the local authorities and installed a rockfall Doppler radar on the 22nd of April. This high-end technology permits to detect rockfalls in real-time. In addition, the rockfall Doppler radar was coupled with traffic lights and alarm horns permitting to close the road and alarm of incoming rockfalls in real-time. SMS and email alarms are also sent in case of events, and both the radar data and live footage from the added pan-tilt-zoom remotely controllable camera are visible from Geoprevent’s online dataportal . This paper looks into the different technologies involved in the alarming system in Vissoie and investigates the main challenges faced during its operation.