Item: Five years experience with avalanche-, mudflow- and rockfall- alarm systems in switzerland
Title: Five years experience with avalanche-, mudflow- and rockfall- alarm systems in switzerland
Proceedings: Proceedings of the 2000 International Snow Science Workshop, October 1-6, Big Sky, Montana
Authors: Hansueli Gubler, AlpuG, Davos , Switzerland
Abstract: Alarm systems detect avalanche flows, mud-flows or the opening of cracks in rock walls and automatically close roads and railway lines with traffic lights in case a dangerous event occurs. Eight new detecting systems have been built in Switzerland during the last five years using technology similar to that used in the Swiss avalanche and natural disaster warning system, IMIS, that consists now of more than 120 remote stations throughout the Swiss Alps. The alarm systems protect two narrow gauge railway lines and four access roads. To detect avalanche flow, three different types of sensors are used in combination: a medium range Doppler radar to detect avalanches already uphill from the detection station, force measurements in steel cables tied across the avalanche track equipped with vertical detecting cables reaching into the dense flow cross section, and geophones to measure vibrations in cables or seismic signals caused by avalanches. Crack openings are measured with special extensometers, mudflow, sediment- and boulder flow using a combined acoustic, force and vibration sensor. All systems are solar powered and radio controlled. Alarm conditions are transmitted as a specially coded short message from the detecting systems to the traffic light control systems. In several cases the traffic light systems are also solar powered. All systems are connected to control centres by radio - phone links. As well as the causes of alarms, system performance is continuously self checked and indicated at the control centres. These setups, based on Campbell loggers, guarantee very high reliability. So far the systems never failed to close traffic lines in cases of avalanches or mud-flows that blocked the road or track.
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Keywords: crack openings, mudflow, rockfall, alarm systems
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