Mapping of unstable and potentially unstable rock slopes in Sogn og Fjordane (work report 2008-20 10)

Abstract

For the past three years NGU has worked on 25 unstable and potentially unstable rock slopes in Sogn og Fjordane. In addition Fjærlandsfjord, Hyenfjord and Årdalsvatnet were systematically mapped for deposits of prehistoric and historic rock slope failures onshore and with help of a bathymetry. Mapping on land included structural mapping of ten sites by on-site field mapping and nine sites by remote structural mapping using terrestrial laser scanning technology (TLS). Field work also included periodic monitoring of 14 sites using differential Global Positioning Systems (dGPS) and TLS at 4 sites. Synthetic Aperture Radar was applied for the entire county but slide velocities could only be mapped out at one locality at Osmundneset (Gloppen municipality). A large amount of work was carried nut on the slope east of Flåm in the Aurland valley, and results have been reported separately (NGU 2011.025). Three large instabilities have been discovered or taken into the monitoring program. These are Osmundneset in Gloppen municipality, Skrednipa in Sogndal municipality, and the Ovris valley in Vik municipality.