WATCHING THE RIFT
One of the most monitored mountains in the world is located in West Norway, in Åknes. Here is why.
In the commune of Stranda, there is a mountain in which there is a 80m thick and 500m wide crack. It is threatening to make 54 million cubicmeters of rocks falling down in Geirangerfjord, triggering a tsunami in it. In the worst case scenario, the wave would be between 50 and 84 meters high and travel in the fjord to Stranda, Geiranger, Hellesylt and surroundings.
The Norwegian Water Resources and Energy Directorate (NVE) is responsible for preventing risks of loss of life, damage to health, the environment and important infrastructures, etc. They work on safety against floods, erosion and landslides, giving advice and guidance to the municipalities and others in spatial planning matters. Their geologists are the ones observing the Åkerneset crack and trying to avoid a catastrophe to happen by draining the rain water that seeps in the rocks and makes the ground more unstable. They install a lot of equipment in field such as bunkers and different kinds of sensors (to insure redundancy, as some kind of sensors are very sensitive and do not always work depending on the extreme weather conditions) to be able to monitor the rift 24/7.
"Geological incidents are very slow"
Every year, the rift widens by 8-9 cm at the top part. It is a lot, but still slow enough to be able to observe unusual movements and warn people on time to evacuate.
Ahead of a landslide, the rocks' movements accelerate, typically over a few weeks/months. By monitoring these movements, landslides can be warned. There are usually three steps in the process to be prepared against lanslides: monitoring, notification and evacuation.
The two last steps change according to the danger zones in which people are. They are determined by NVE in collaboration with other geotechnical bodies, while the evacuation zone is determined by the police, in consultation with NVE, local authorities and affected residents and businesses. They can then decide the "safety margin" according to the vulnerability of people living there (if there are many in an area, the safety margin should be bigger to give them more time to evacuate).
According to the observed movements in the crack, different danger levels can be defined, as on the table.
The NVE is responsible for determining and notifying a changed danger level to the police and county governor who will then inform people in the area.
The information campains will be spread through mass media, but also through other systems if considered localy necessary. Each municipality must have a plan for population alert, based on the municipality's overall risk and vulnerability analysis.
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So, imagine you are in Hellesylt. Here is what would happen if the landslide falls.
Schematic representation of the expected development of a landslide.
Schematic representation of the expected development of a landslide.
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A webdocumentary made by Marica Hass, Louis Selfslagh, Cybil Delbrouck, Izar Martin & Leah Kerzbeck.
