Radar system monitors Pizzo Cengalo, Bondo

Sep 6, 2017News, Rock

On 23 August 2017, a large rockfall occurred at Pizzo Cengalo in the Bregaglia region at the Swiss-Italian Border. Around 3 million m³ of rock broke off the unstable North face of the mountain and formed a large debris flow that reached the riverside village of Bondo (National GeographicNew York Times, BBC). The debris flow triggered our alarm system at Bondasca river and automatically closed roads in Bondo and informed the responsible authorities. Since a main rockfall in 2011, the mountain has been closely monitored and preventative measures have been taken. The authorities invested in a large catch basin for the river as well as our alarm system to detect a potential debris flow before it reaches the village. Considering the vast extent of the event, the resulting damage in the village was relatively small. The preventative efforts clearly paid off.

However, the event on 23 August 2017 did not release all unstable material. Further instabilities in the mountain’s North face were identified but clean-up operations had to go on. Therefore, an extended monitoring and alarm system was required to guarantee safety for the workers and the village.

Consequently, we installed two more stations in addition to the already existing alarm system. At Sciora hut, an interferometric georadar was set up that serves as warning system for further rockfall at Pizzo Cengalo. The radar continuously monitors the break-off zone and detects sub-mm deformations in all-weather as well as at any time of the day. The system allows to predict imminent break-offs and to implement according measures if necessary (e.g. interrupt clean-up operations).

Further down valley and at the Bondasca river, the alarm system was extended by a second station with a longer warning time. The system now consists of the following detection stations:

  • Prä Alp (existing since 2012)
    Two gauge radars and two live cameras.
    Warning time: 2 min
  • Lera Alp (new)
    Two gauge radars, three seismometers, one live camera
    Warning time: 4 min

Several redundancy levels provide fail-safe energy supply for the stations. Data and alarm transfer is carried out by several redundant communication means, such as radio, WLAN, GSM, DSL and fibre. In case the alarm system detects a debris flow, it automatically informs the authorities, the workers in the catch basin and switches the traffic lights to red at the bypass road.

Several smaller rockfall and debris flow events have occurred since the system was extended. Thanks to the monitoring it was possible to predict an imminent rockfall of about 400’000 m³ and the alarm system successfully detected the debris flows (swissinfo). Detailed information about this comprehensive system at Bondasca valley is provided here.

Geopraevent is a technology company based in Zurich focussing on developing, installing and operating customized alarm and monitoring systems for natural hazards. Learn more about Geopraevent here.

Transportation of the radar system to the optimal monitoring location. Read here more on how to find the optimal location.