DEBRIS FLOWS: IN COURMAYEUR (ITALIAN ALPS) A VIRTUOUS EXAMPLE OF RISK MANAGEMENT

One of the two traffic lights, installed in 2017

On the 5th of August 2022, a debris flow occurred at the Rochefort stream in the hamlet of La Palud, Courmayeur (Italy). This event invaded with mud and large boulders the carriageway of the road leading to Val Ferret valley, significantly damaging the bridge crossing the Rochefort stream. The debris flow did not significantly affect people and vehicles that were about to pass also thanks to the automatic switching on of two special traffic lights. This landslide also damaged the aqueduct that serves Courmayeur, generating a few days of disruption during the holiday period, as also reported by the national media.

In 2017, by the will of the Valle d’Aosta region environmental office, a monitoring and alarm system was installed, on an experimental basis, in the event of a debris flow would affect the Rochefort steam, to promptly interrupt traffic in both directions using a traffic light system. The system, called ALMOND-F (ALarm and MONitoring system for Debris-Flow), was installed along the stream a few tens of meters upstream of the road bridge. Starting from 2019, after the experimental phase, the system has been taken over at the administrative level by the Municipality of Courmayeur.
The ALMOND-F system is an excellent example of fruitful collaboration between public research, local administrations and private companies as its implementation demonstrates the synergy between the Research Institute for Hydrological Protection (CNR-IRPI), developer of the EAGLE-DFO algorithm (EArly Ground-vibration Learning of Debris-Flow Occurrence), capable of recognizing debris flows on the basis of ground vibrations (seismic waves) produced by the moving material, detected by geophones, and Siap+Micros S.p.A. who oversaw the development of the system starting from electronic design and implementation up to installation, configuration, remote surveillance and maintenance.

On August 5th, 2022, the ALMOND-F alarm system worked regularly and effectively, activating the traffic lights and interrupting traffic a few (2 ÷ 3) minutes before the debris flow invaded the bridge and roadway. The system also reported the occurrence of the event via e-mail and SMS to local authorities in real time, also taking a sequence of photographs of the bridge before and after the arrival of the flow, thus showing the debris deposited and the conditions of the road after the event, before any field inspection.
It should be noted that, in the previous five years of operation, the system has always been found to be operating correctly, without ever producing false alarms.

The bridge a moment before and after the arrival of the debris flow