1. Understanding long-term slope deformation for
stability assessment of rock slopes: The case of
the Oppstadhornet rockslide, Norway
Reginald L. Hermanns
Thierry Oppikofer, Halgeir Dahle, Trond Eiken,
Susan Ivy-Ochs, Lars Harald Blikra
Vajont conference, Padova, October 8th -10th, 2013
2. Content
• Characterisation of fjord lands
• Systematic mapping program for unstable rock slopes in Norway
• Oppstadhornet rockslide in western Norway
• Unstable rock slopes and deglaciation in Norway
10. Certain fjellskred events
Name
Tjelle
Tafjordulykka
Skafjellet
Lausneset
Loenulykke 1
Loenulykke 3
Pollfjellet
County
Møre og Romsdal
Møre og Romsdal
Møre og Romsdal
Møre og Romsdal
Sogn og Fjordane
Sogn og Fjordane
Troms
Municipality
Nesset
Norddal
Stranda
Stranda
Stryn
Stryn
Lyngen
Year
1756
1934
1731
1300
1905
1936
1810
Municipality
Sande
Stranda
Stranda
Norddal
Gaular
Årdal
Year
1700
1749
1938
1811
1786
1983
Volume
Displaceme
[Mm3]
Lives
nt wave
15.0
32
Yes
3.0
40
Yes
6.0
17
Yes
0
Yes
0.4
61
Yes
1.0
74
Yes
14
Yes
Uncertain fjellskred events
Name
Storefonna
Geirangerfjorden
Skafjellet
Arnafjord
Hestadfjorden
Årdalsfjorden
County
Møre og Romsdal
Møre og Romsdal
Møre og Romsdal
Sogn og Fjordane
Sogn og Fjordane
Sogn og Fjordane
Volume
[Mm3]
0.1
0.4
0.2
Lives
0
0
0
45
0
0
Displaceme
nt wave
Yes
Yes
Yes
Yes
Yes
Yes
11. Systematic mapping program for unstable rock slopes in Norway
Tafjord 1934
Assumption:
• Slow deformation indicating slope instability
• Acceleration phase prior to collapse
12. Systematic mapping program for unstable rock slopes in Norway
Task:
•
•
•
•
Tafjord 1934
Find all unstable rock slopes which may collapse catastrophically
Understand geologic condition of each unstable slope
Rank all slopes based upon their hazard and risk
24/7 monitoring and early warning
Mapping approach:
• Risk based
21. Oppstadhornet rockslide in western Norway
10Be
exposure age
4.50 m
4
5
6600
4.00 m
3200 a
0.1 mm/a
2.05 m
10300
2.20 m
1.1
3
0.4 mm/a
2.10 m
1.6
2
1700 a
2.2 mm/a
12500
2.85 m
3.2
1
700 a
22. Oppstadhornet rockslide in western Norway
10Be
exposure age Slip rate
2.10 m
3
2.05 m
10300
2.20 m
4
5
6600
4.00 m
2.2 mm/a
2
1700 a
3.2
1
12500
2.85 m
3200 a
700 a
Start of sliding: 14.2 ka ago (16.6 ka)
4.50 m
23. Why did the Oppstadhornet slope did not failed
during a seismic event in the geological history?
28. Conclusion
• In fjord lands is the area of impact of rock slides often larger than in normal
mountain settings
• Norwegian fjord land is densely settled and systematic mapping is
necessary in order to be able to prepare for future events
• Oppstadhornet rockslide is a typical rockslide in western Norway that has
large consequences
• Oppstadhornet has moved constantly with low rate and is still moving
• Movement started 14 ka ago when the top came out of the ice
• Other landslides have been moving since the location melted out of the ice
sheet with low rate
• Long term slip rates are important information to detect acceleration
29. Thank you for your attention
Reginald.Hermanns@NGU.NO