Regional Mountain Conference

The Simplon pass culminates at 2006 m over sea and is one of the principal alpine roads crossing the Alps in the North-South direction. It is extremely important for intra-European goods transportation, because it is open all year round. As it is only protected by avalanche galleries and does not cross a tunnel, dangerous goods like chemicals can be transported safely on this road, making this road even more important.

On the 29th of June 2025 at about 4.30 PM, following a few days of high intensity precipitation, several massive debris flows originating from the region of the Hübschhorn rock glacier entered the Engi gallery that is normally protecting the road from avalanches in winter.  More than one meter of debris was deposited inside the gallery, causing the closure of the road. The Hübschhorn rock glacier had been melting substantially over the last decade so that a combination of high temperature and important cumulative precipitation could mobilize the debris. The road had to be reopened as rapidly as possible. To do so, the debris flow channel had to be raised to avoid new damage to the road in case of new events, but this meant performing construction works in a region with frequent rockfall and high debris flow risk. Therefore, the Federal Roads Office mandated Geoprevent to rapidly install both a monitoring system, to provide information about the state of the rock glacier, as well as a multi-component alarming system to detect debris flows and rockfall. The alarming system could close the road and trigger a local alarm on the construction site in case of detections.

This work introduces the different components of these complex monitoring and alarming systems and presents some insights into the challenges faced during their installation and operation.