DEALING WITH GEOLOGICAL HAZARDS
nate frictionless sliding planes due to the high-water content. The study and surveys will include new boreholes and instruments and focus on how the water flows in the mountainside and whether it is possible to drain the water or not. Let us hope that the project gives good results.5,6
Places to study rock mass slides and geohazards in Norway
There are many places to study rockslides and related geohazards in Norway. Amongst the most common places are: The Norwegian University of Science and Technology, the University of Oslo, The Arctic University of Norway, Western Norway University of Applied Sciences and the University of Bergen, all of which offer international courses at different levels, as well as various field courses.
Epilogue
rest of the unstable area. The high corre- lation between precipitation and move- ment lead to an attempt to trigger the rock slide by adding a massive volume of water in the autumn of 2017, when there once again was a red danger signal. Despite the increased movement during the addition of the water, the experiment did not trigger the rockslide. The experi- ment failed and was not continued due to bad weather, and the task used a lot of resources but contributed valuable information about water content and movement.3
Monitoring the Man
The Man is continuously monitored with multiple types of instruments. A GPS-network with 8 antennas is placed all over the rock masses. A laser sys- tem is monitoring movements in the upper part, there are extensometers, geophones, cameras, tiltmeter, 2 ground based InSAR-radars, 2 boreholes with instruments and a weather station. The instruments measuring the surface movements and the deep boreholes make it possible to cover different parts of the mountainside. The infrastructure is robust and is designed to transmit con- tinuously, including when parts of the monitoring instruments are broken due to a rock mass slide. In addition to the monitoring system, there is also a focus on the timing of warnings. The discus- sion amongst the responsible geologists about when to warn depends for the most
www.aipg.org
part on threshold values, experiences from other cases worldwide, and good expertise. The advice from the geologists may have major consequences for those who are affected.4,5
Åknes Norway is known for its steep moun-
tains and deep fjords. Along with this spectacular nature comes a somber real- ity. The Man is but one out of seven unstable mountainsides in Norway that is considered as a high-risk object and is under continuous monitoring. Åknes is located by Sunnylvsfjorden and is another monitored mountain side. The estimated volume of the rock mass from a rock mass slide will create a tsunami which will destroy several settlements along the fjord. The tsunami will become amplified due to the depth of the fjord and the tall and narrow mountainsides, and it is estimated that the wave may reach as high as 85 meters. The people living by these fjords will have only a few minutes to evacuate. This sce- nario is dramatized in the movie “The Wave”. Therefore, monitoring and warn- ing routines are vital for the affected people. The monitoring consists of seis- mographs, georadar, lasers and reflec- tors, geophones, cameras, metrological instruments, extensometers, electrical resistivity surveys, GPS, boreholes and video inspections of the boreholes. There is also an ongoing project concerning drainage. The aim is to try to stabilize the mountainside by draining it to elimi-
Back in the Romsdalen valley in the late spring of 2015, the bus finally makes a stop and we step off to check if The Man had fallen or not. He hadn’t and he hasn’t yet!
References
1. Skrede, I., Kristiansen, L. & Hole, J. (2015). Geologisk evaluering av Veslemannen -eit mindre fjellskred i utvikling. Norges vassdrags- og ener- gidirektorat (NVE), 1-34 pp. [http://
publikasjoner.nve.no/rapport/2015/ rapport2015_41.pdf]
2. Dahle, H., Anda, E., Saintot, A. & Sætre, S. (2008). Faren for fjellskred fra
fjellet Mannen i Romsdalen.
Norges geologiske undersøkelse, 1-21 pp. [
http://aps.ngu.no/pls/oradb/ rf.Visdok?c_dokid=0000054578]
3. NVE (2018). Vanntiltak Veslemannen: Effekt av forsøk med ekstra vanntil- førsel i 2017 og vurdering av fremti- dige tiltak. Faktaark nr. [01/2018], 1-5 pp. [
http://publikasjoner.nve.no/ faktaark/2018/faktaark2018_01.pdf]
4. NVE (2015). Mannen – fjellskre- dovervakning. [
https://www.nve.no/ flaum-og-skred/fjellskredovervaking/ mannen/]
5. Personal correspondence with Lars Harald Blikra, Head of Section for Rockslides at The Norwegian Water Resources and Energy Directorate (NVE) (February 2019).
6. NVE (2016). Åknes – fjellskredover- vakning. [
https://www.nve.no/flaum- og-skred/fjellskredovervaking/%C3% A5knes/]
Jul.Aug.Sep 2019 • TPG 13
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