Rock slope instabilities in Norway: First systematic hazard and risk classification of 22 unstable rock slopes from northern, western and southern Norway

Abstract. Permafrost in steep rock slopes has been increasingly studied since the early 2000s in conjunction with a growing number of rock slope failures, which likely resulted from permafrost degradation. In Norway, rock slope destabilization is a widespread phenomenon and a major source of risk for the population and infrastructure. However, a lack of precise knowledge of the permafrost distribution in steep slopes hinders the assessment of its role in these destabilizations. This study proposes the first nationwide permafrost probability map for the steep slopes of Norway (CryoWall map). It is based on a multiple linear regression model fitted with multi-annual rock surface temperature (RST) measurements, collected at 25 rock slope sites, spread across a latitudinal transect (59–69∘ N) over mainland Norway. The CryoWall map suggests that discontinuous permafrost widely occurs above 1300–1400 and 1600–1700 m a.s.l. in the north and south rock faces of southern Norway (59∘ N), respectively. This lower altitudinal limit decreases in northern Norway (70∘ N) by about 500±50 m, with a more pronounced decrease for south faces, as a result of the insolation patterns largely driven by midnight sun in summer and polar night in winter. Similarly, the mean annual RST differences between north and south faces of similar elevation range around 1.5 ∘C in northern Norway and 3.5 ∘C in southern Norway. The CryoWall map is evaluated against direct ice observations in steep slopes and discussed in the context of former permafrost studies in various types of terrain in Norway. We show that permafrost can occur at much lower elevations in steep rock slopes than in other terrains, especially in north faces. We demonstrate that the CryoWall map is a valuable basis for further investigations related to permafrost in steep slopes in terms of both practical concerns and fundamental science.

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A decision analysis framework for the assessment of likely post-failure velocity of translational and compound natural rock slope landslides

Canadian Geotechnical Journal ◽

10.1139/t07-082 ◽

2008 ◽

Vol 45 (3) ◽

pp. 329-350 ◽

Cited By ~ 12

Author(s):

James Glastonbury ◽

Robin Fell

Keyword(s):

Decision Analysis ◽

Decision Trees ◽

Rock Slope ◽

Safety Management ◽

Rock Slopes ◽

Analysis Framework ◽

Slide Mass ◽

Critical Areas ◽

Natural Rock ◽

Hazard And Risk

An integral component of the assessment of hazard and risk for landslides from large natural rock slopes is the examination of the likely consequences associated with failure. This in turn is inherently related to the post-failure velocity of the slide mass. This paper presents a decision analysis framework for assessment of the post-failure velocity of such slopes. The paper includes discussion of characteristics that influence the post-failure velocity and presents decision trees and supporting matrices to allow assessment of the likely post-failure velocity of translational and internally sheared compound landslides. These represent the most common classes of large rock landslides. The framework is based on data gathered from a large number of landslides from natural rock slopes and incorporates information from a study of excavated rock slopes. These landslides have been studied to determine the factors and characteristics of rock slope failures that influence the post-failure velocity. The framework provides an ability to semiquantitatively assess the uncertainty in prediction of the likely post-failure velocity and identify critical areas of investigation, which would allow for reduction of this uncertainty. The method is expected to be of most use in a quantitative or qualitative risk-based analysis for landslide safety management.

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Evolution of events before and after the 17 June 2017 rock avalanche at Karrat Fjord, West Greenland – a multidisciplinary approach to detecting and locating unstable rock slopes in a remote Arctic area

Earth Surface Dynamics ◽

10.5194/esurf-8-1021-2020 ◽

2020 ◽

Vol 8 (4) ◽

pp. 1021-1038

Author(s):

Kristian Svennevig ◽

Trine Dahl-Jensen ◽

Marie Keiding ◽

John Peter Merryman Boncori ◽

Tine B. Larsen ◽

...

Keyword(s):

Multidisciplinary Approach ◽

Rock Slope ◽

Rock Avalanche ◽

Rock Slopes ◽

Slope Failures ◽

West Greenland ◽

Arctic Regions ◽

Rock Avalanches ◽

Dip Slope ◽

Unstable Rock

Abstract. The 17 June 2017 rock avalanche in the Karrat Fjord, West Greenland, caused a tsunami that flooded the nearby village of Nuugaatsiaq and killed four people. The disaster was entirely unexpected since no previous records of large rock slope failures were known in the region, and it highlighted the need for better knowledge of potentially hazardous rock slopes in remote Arctic regions. The aim of the paper is to explore our ability to detect and locate unstable rock slopes in remote Arctic regions with difficult access. We test this by examining the case of the 17 June 2017 Karrat rock avalanche. The workflow we apply is based on a multidisciplinary analysis of freely available data comprising seismological records, Sentinel-1 spaceborne synthetic-aperture radar (SAR) data, and Landsat and Sentinel-2 optical satellite imagery, ground-truthed with limited fieldwork. Using this workflow enables us to reconstruct a timeline of rock slope failures on the coastal slope here collectively termed the Karrat Landslide Complex. Our analyses show that at least three recent rock avalanches occurred in the Karrat Landslide Complex: Karrat 2009, Karrat 2016, and Karrat 2017. The latter is the source of the abovementioned tsunami, whereas the first two are described here in detail for the first time. All three are interpreted as having initiated as dip-slope failures. In addition to the recent rock avalanches, older rock avalanche deposits are observed, demonstrating older (Holocene) periods of activity. Furthermore, three larger unstable rock slopes that may pose a future hazard are described. A number of non-tectonic seismic events confined to the area are interpreted as recording rock slope failures. The structural setting of the Karrat Landslide Complex, namely dip slope, is probably the main conditioning factor for the past and present activity, and, based on the temporal distribution of events in the area, we speculate that the possible trigger for rock slope failures is permafrost degradation caused by climate warming. The results of the present work highlight the benefits of a multidisciplinary approach, based on freely available data, to studying unstable rock slopes in remote Arctic areas under difficult logistical field conditions and demonstrate the importance of identifying minor precursor events to identify areas of future hazard.

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Monitoring Rock Slope Instabilities Using Frequency Domain Decomposition Modal Analysis

10.5194/egusphere-egu21-6390 ◽

2021 ◽

Author(s):

Mauro Häusler ◽

Clotaire Michel ◽

Jan Burjánek ◽

Donat Fäh

Keyword(s):

Domain Decomposition ◽

Resonance Frequency ◽

Modal Analysis ◽

Frequency Domain ◽

Normal Mode ◽

Rock Slope ◽

Damping Ratio ◽

Slope Instabilities ◽

Frequency Domain Decomposition ◽

Unstable Rock

Measuring ambient seismic vibration provides a promising tool to monitor unstable rock slopes due to its independence from actual surface deformations. It is generally observed that the seismic wavefield, arising from ambient vibrations, polarizes perpendicular to open fractures and that unstable slopes exhibit strong wavefield amplifications compared to stable reference sites. Rock slope instabilities dominated by deep persistent fracture sets exhibit normal mode behaviour due to standing wave phenomena within individual compartments of the unstable volume. Techniques to assess such behavior are well established in mechanical and civil engineering to assess the dynamic response and possibly the structural integrity of the structure studied.&#160;We performed enhanced frequency domain decomposition modal analysis on ambient vibration data acquired in real-time on an unstable rock site with a volume larger than 150,000&#160;m3 near Preonzo, Switzerland. We tracked the resonance frequency and normal mode polarization of the first two modes over a period of four years. In addition, we show the development of the modal damping ratio of the fundental mode over time, which is a measure of energy dissipation within and out of the system. We found that the dynamic properties of the rock structure experienced annual variations and that they are primarily controlled by temperature and only secondarily by the exension and closure of large-scale fractures. Even though no large slope failure was observed during the monitoring period, the dataset provides a reference model for ongoing slope monitoring, as the resonance frequency and damping ratio is expected to change significantly prior to failure.

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Ambient vibration classification of unstable rock slopes: A systematic approach

Engineering Geology ◽

10.1016/j.enggeo.2018.12.012 ◽

2019 ◽

Vol 249 ◽

pp. 198-217 ◽

Cited By ~ 15

Author(s):

Ulrike Kleinbrod ◽

Jan Burjánek ◽

Donat Fäh

Keyword(s):

Systematic Approach ◽

Ambient Vibration ◽

Rock Slopes ◽

Unstable Rock

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Improvements of safety conditions of unstable rock slopes through the use of explosives

Natural Hazards and Earth System Science ◽

10.5194/nhess-8-473-2008 ◽

2008 ◽

Vol 8 (3) ◽

pp. 473-481 ◽

Cited By ~ 1

Author(s):

M. Casale ◽

C. Oggeri ◽

D. Peila

Keyword(s):

Detailed Analysis ◽

Rock Slope ◽

Rock Slopes ◽

Advantages And Disadvantages ◽

Unstable Rock

Abstract. The paper discusses operations aimed at creating a safer natural or man made rock slope by artificially inducing the displacement of unstable elements by blasting. A detailed analysis of the problems with the use of explosives present when conducting these activities is carried out focusing on the advantages and disadvantages of this technology. The results of two examples of demolition of instable rock elements are presented and discussed thus providing suggestions for future blasting designs.

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Use of Satellite and Ground Based InSAR in Hazard Classification of Unstable Rock Slopes

Landslide Science for a Safer Geoenvironment ◽

10.1007/978-3-319-05050-8_60 ◽

2014 ◽

pp. 389-392 ◽

Cited By ~ 2

Author(s):

John F. Dehls ◽

Tom Rune Lauknes ◽

Reginald L. Hermanns ◽

Halvor Bunkholt ◽

Tom Grydeland ◽

...

Keyword(s):

Rock Slopes ◽

Hazard Classification ◽

Unstable Rock

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Semi-automated regional classification of the style of activity of slow rock-slope deformations using PS InSAR and SqueeSAR velocity data

Landslides ◽

10.1007/s10346-021-01654-0 ◽

2021 ◽

Author(s):

Chiara Crippa ◽

Elena Valbuzzi ◽

Paolo Frattini ◽

Giovanni B. Crosta ◽

Margherita C. Spreafico ◽

...

Keyword(s):

Rock Slope ◽

Progressive Failure ◽

Principal Component ◽

Cost Effective ◽

Displacement Rate ◽

Machine Learning Classification ◽

Management Perspective ◽

Alpine Environments

AbstractLarge slow rock-slope deformations, including deep-seated gravitational slope deformations and large landslides, are widespread in alpine environments. They develop over thousands of years by progressive failure, resulting in slow movements that impact infrastructures and can eventually evolve into catastrophic rockslides. A robust characterization of their style of activity is thus required in a risk management perspective. We combine an original inventory of slow rock-slope deformations with different PS-InSAR and SqueeSAR datasets to develop a novel, semi-automated approach to characterize and classify 208 slow rock-slope deformations in Lombardia (Italian Central Alps) based on their displacement rate, kinematics, heterogeneity and morphometric expression. Through a peak analysis of displacement rate distributions, we characterize the segmentation of mapped landslides and highlight the occurrence of nested sectors with differential activity and displacement rates. Combining 2D decomposition of InSAR velocity vectors and machine learning classification, we develop an automatic approach to characterize the kinematics of each landslide. Then, we sequentially combine principal component and K-medoids cluster analyses to identify groups of slow rock-slope deformations with consistent styles of activity. Our methodology is readily applicable to different landslide datasets and provides an objective and cost-effective support to land planning and the prioritization of local-scale studies aimed at granting safety and infrastructure integrity.

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