Radar monitors avalanches on Strynefjell

Many people have travelled by car from Lom over Strynefjell, onto the tourist road with road number 63 at Stavbrekka and down to Geiranger. The road is closed throughout the winter. The reason is large avalanches.

It's always uncertain when an avalanche will occur, but it's absolutely certain that it will. Since 2015, the snow masses that are guaranteed to thunder down the tourist route and into Lake Langevatnet have been monitored by radar as research and studies to see if it is possible to keep the road open. This presupposes that it must be possible to warn of the avalanche in advance.

Norwegian Cautus Geo AS specialises in monitoring and warning of natural hazards. They have developed various measurement systems for warning of avalanches. Since March this year, the latest radar system has been used by the Norwegian Public Roads Administration on Strynefjellet.

- Radar monitoring is a new way of managing avalanche risk and increasing the safety of those travelling on the roads. At Strynefjellet, we are monitoring a large area of snow with millimetre accuracy. How fast the snowpack moves determines how close in time we are to this year's major avalanche at Stavbrekka," says Lars Krangnes.

The radar Cautus Geo has established at Stavbrekka is the latest generation.

- "It measures with greater accuracy than the radars we've had before. We're talking about a new generation," says Atle Gerhardsen.

Cautus Geo has developed an entire system of monitoring and alerting.

- The data is fed into our own developed web system. The data is analysed continuously and is always available. The system shows exactly what is happening on the mountain. All abnormal changes are automatically signalled," says Lars Krangnes.

Many roads are closed in winter due to the high risk of avalanches. The solution for a safe winter road is often to build a tunnel. This is both time-consuming and expensive.

- Measuring equipment monitors and warns, and are reasonable measures to ensure that landslides do not harm road users," says Lars Krangnes.

Snow avalanches are dangerous. Avalanches like the one we're talking about at Stavbrekka on Strynefjellet are of the most dangerous type.
Over the past ten years, 79 people have lost their lives in avalanche accidents. This winter alone, NGI, which has been researching avalanches since 1972, has registered 11 avalanche deaths in its database.

Also monitoring in Sogn and Telemark

Cautus Geo has also established systems for monitoring and warning of avalanches in Sogn and Telemark.

In Utladøla in Sogn, radar monitoring and avalanche warning has been established. The system has been in operation there since 2016.

- "A major advantage of radar is that it is not affected by light or precipitation. We see that the system is reliable," says Lars Krangnes.

In Telemark, Cautus Geo has delivered a different system. It is geophone-based and is located at Tinnsjøen. It measures landslides based on vibrations in the ground.

- The tremors show when landslides occur and how big they are," says Lars Krangnes.

FACTS: New generation of radar technology

• A new generation of ground-based InSAR radar is used at Stavbrekka. It moves back and forth on a three-metre rail and takes radar images at close intervals. Each measurement round generates a 2D analysis. Measurement accuracy is less than 1 mm for each measurement cell.
• The radar is not affected by weather conditions, heavy snow drifts or light conditions. It measures and generates 2D analyses around the clock.
• The radar is located 1,000 metres from the measurement area, up on the mountainside on the opposite side of Langevatnet on national road 15 towards Stryn.

FACTS: When is the Stavbrekka landslide triggered?

• 2014: 22 April.
• 2015: 6 May.
• 2016: 7 May.
• 2017: 16 May.
• 2018: 20 April