Its been 12 years since the last time avalanche researchers at the Norwegian Geotechnical Institute (NGI) conducted a successful full-scale avalanche experiment. On Sunday, April 11th, with massive pieces of instrumentation in place, the conditions were prime and they triggered a slide with a 200 meter crown that sent between 10,000-20,000 cubic meters of snow downhill at a whopping 180 km/h (111mph). With the data collected scientists can better understand avalanche dynamics and forces which in turn can be used to make safer building and roadways. One thing is for sure, snow science can be ultra rad. Fire in the hole!
PRESS RELEASE: A perfect slide for learning
Between 10,000 – 20,000 cubic meters of snow began to rumble down the avalanche at Ryggfonn, NGI’s full-scale test field at Strynefjellet, and tore the snow along the course. It has been ten years since new measuring instruments were installed. Since then, researchers have had to be patient in anticipation of finding the perfect conditions for the perfect landslide test.
– The experiment exceeded expectations, and we are very pleased with the results. We consider that the landslide had a breaking edge with a length of over 200 meters. On a scale from 1-5, the landslide had a size of 4. In other words, this was a large landslide – exactly what we want for these experiments. The radar measurements indicate that the landslide had a speed of up to 50 meters per second, ie 180 km / h, says project engineer Henrik Langeland, NGI’s landslide expert in Stryn.
NGIs unique role
Ryggfonn is one of two avalanche tracks in the world that can perform this type of instrumented large-scale experiment. The second landslide is in Switzerland.
The avalanche track, from the loosening area to the avalanche embankment and the latest measuring instruments, has a height difference of 900 meters and a distance of over 1.5 kilometers. We are thus dependent on the snow conditions being suitable for the landslide to be large enough, says Langeland.
The results from these landslide experiments will provide a better basis for planning security measures in connection with the development of infrastructure and buildings. With the help of successful experiments, the researchers will be able to develop improved calculation models for avalanche loads, which includes very advanced physics.
An avalanche must be planned
Much must be in place before a landslide can be triggered manually, and the researchers have only a small time window where the experiment can be carried out with optimal conditions. The snow must be unstable enough, and there must be sufficient visibility and light to be able to see and film the avalanche, and ensure safety.
– This is not a cordoned off area, so before each blasting operation we must fly over the area to ensure that there are no people or animals nearby. Strynefjellet is a widely used hiking terrain and for example reindeer can in some conditions go into this area, Langeland explains.
When the landslide is triggered, speed and pressure are measured at several robust installations down the landslide, among other things. Before the operation, a drone survey is carried out to create a surface model of the terrain, and the same drone survey is carried out after the landslide has been triggered and stopped at the bottom of the valley. The difference between the models gives a detailed landslide volume and affected area of the landslide, ie outlet length and landslide width.
– After the landslide has been triggered and data secured, a major job begins to analyze the data collected. The analyzes can be compared with previous landslide data from Ryggfonn and will be systematized to provide learning about the phenomenon through, for example, improved models for hazard assessments for buildings and infrastructure, says Langeland.
NGI was assigned responsibility for avalanche research in Norway in 1972
Until the 1970s, the organization of landslide prevention work in Norway was deficient. Several committees were set up to map out how such an organization could best be implemented. This resulted in NGI in 1972 in Report to the Storting no. 9 being given responsibility for avalanche research in Norway, a role that NGI still has. Today, avalanche research is funded through a direct grant from the Storting, which is managed by NVE – the Norwegian Water Resources and Energy Directorate.