An Early Warning System for Debris Flows and Snow Avalanches

To protect a mountain road against debris flows and snow avalanches that occur periodically along a gully, an innovative monitoring and early warning system (EWS) was designed, installed and tested. The system is based on a detection section equipped with 3 inclinometers suspended above the gully located at approximately 120 m upstream from the road, by two traffic lights, a weather station and two cameras. A wireless sensor network is used to manage the system so that all sensors and equipment can communicate through radio signal, without the need of cables. This solution was also chosen to reduce the overall environmental impact of the installation which took place in the Gran Paradiso National Park, in the North Western Italian Alps. In the case of an event, the detection section is triggered directly by the passage of the debris or the avalanche. An alarm data package is generated and transmitted to turn to red two traffic lights on the road thus stopping traffic. The paper will describe the monitoring and early warning system. Moreover, it will show how data collected by the weather station are used to manage in real time the attention and alarm thresholds allowing for limiting human intervention on the system and anticipating the increased probability of occurrence of events. Finally, a snow avalanche event occurred on the 8th January 2018 and detected by the early warning system will be illustrated.