Full scale avalanche test
Ryggfonn in the Stryn Mountains in western Norway is the name of NGI's field laboratory for avalanche research. Experts can here closely examine and study avalanches in its natural environment and in full scale. Just before Easter 2007, a new "Ryggfonn field mission" was conducted.
After comprehensive preparations and a few uncertain factors concerning the weather and snow conditions, an avalanche was triggered on the 22dn of March at 3.55pm. Many excited researchers were on the site to study the results.
An International Project
Ryggfonn is one of the few large avalanche paths that are instrumented for full scale tests and experiments. These tests make up the field part of the project "Avalanche Studies and Model Validation in Europe". NGI is in charge of the project, which included researchers from; Institut für Lawinen- und Wildbachforschung, Innsbruck, Wildbach- und Lawinenverbauung/WLV Tirol, International Centre for Geohazards, Universitat de Barcelona, the Norwegian Armed Forces Winter School, as well as NGI.
Methods
The avalanche was triggered by 275 kg explosives placed on the top of the mountain in the avalanche release area. The snow topography had been thoroughly mapped in advance with a laser scanner. New measurements made right after the avalanche had settled gave very precise estimates about the change in volume between the release and the new deposition, and thereby also a quantification of the erosion along the avalanche path. The avalanche path is also equipped with pressure and vibration sensors.
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| The avalanche came to rest in front of the catching dam in end of the avalanche path. |
Finally, the avalanche was filmed and photographed from different angles and internal avalanche movement was measured with two Doppler radars in the valley below. A 16 m high catching dam on the valley floor has been constructed, with the ability to investigate the interaction between the avalanche and such constructions that are intended to stop or reduce the effects of the avalanche.
The artificial avalanche was of medium size and consisted of mixed forms of snow. In the upper part the snow was light and dry, but towards the bottom it became more moist and heavier. The data gathered from the experiment will be used to develop new dynamic avalanche models that are important tools for the improvement of avalanche maps and when developing methods to reduce the dangers of avalanches.
Happy project participants, Hedda Breien and Peter Gauer,
at one of the birds eye view spots to follow the avalanche.