Luzia Fischer

Systematic Mapping of Large Unstable Rock Slopes in Norway

Historically, large rock slope failures impacting into a fjord and causing a several tens of metre high displacement wave have been one of the natural hazards in Norway claiming most lives. In the last 7 years, the Geological Survey of Norway has implemented a systematic mapping approach to characterize unstable rock slopes prone to catastrophic failures, so that future events can be recognized beforehand and society can adapt to the hazard. Systematic mapping has been carried out in three countries and more than 285 unstable slopes have been found. Of these sites, 62 are monitored periodically and 4 have been characterized as high risk objects with continuous monitoring systems installed. In order to classify the likelihood of a future event, rock slope mapping of each object includes the analyses of slide kinematic, velocity of the slide accompanied with other indicators of slide activity and an analysis of recurrence of previous events along the slope.

Hazard and Risk Classification for Large Unstable Rock Slopes in Norway

We present a classification system for hazard and risk that is posed by unstable rock slopes in Norway that might undergo catastrophic failure in future and can cause loss of life. The system is scenario-based as the intensity and rate of displacement, as well as the geological structures activated by the sliding rock mass vary significantly on the slopes. In addition, for each scenario the secondary effects, such as genera- tion of displacement waves or landslide damming of valleys with the potential of later outburst floods, are evaluated. The hazard analysis is based on two types of criteria: 1) Structural site investigations including analysis of the development of a back-scarp, lateral boundaries and basal sliding surface. This includes a kinematic analysis for sliding and toppling based on slope orientation, persistence of main structures and morphologic expressions of the sliding surface. 2) Analysis of slope activity primarily based on slide velocity, change of deformation rates, observation of rockfall activity, and historic or prehistoric events. The analysis of consequences focuses on the potential fatalities to the rock slide scenarios and secondary ef- fects. Based on the hazard and consequence analysis each scenario is classified in a risk matrix into cat - egory low, medium or high risk.

Detecting Potential Climate Signals in Large Slope Failures in Cold Mountain Regions

Concern and interest are rising that climate change may have an adverse impact on slope stability in mountain regions. Rock slopes in high mountain areas with glaciers and permafrost are particularly sensitive to atmospheric warming. In fact, several large rock slope failures have been observed in high mountain areas around the world in recent years. However, the detection of changes in the frequency or magnitude of such slope failures is fraught with a number of difficulties and has only recently been addressed. Here we outline several approaches that could be used to detect a change in high mountain slope failure activity. Rather than present research results, we provide a conceptual design of how research in this field could be strengthened.

Database of Unstable Rock Slopes of Norway

The Geological Survey of Norway is currently developing a database for unstable rock slopes in Norway. The database is intended to serve three main purposes: (1) to serve as a national archive for potential unstable slopes for use in hazard and risk analysis, aerial planning and mitigation work as well as research; (2) to serve as a robust and easy to use database during field mapping of unstable rock slopes; (3) provide a public available database accessible through an online web map service. The database structure contains several feature classes storing both raw and processed data, including structures, lineaments, displacement measurements, run-out areas and other observations. All feature classes are linked to one main point which holds a general summary for each unstable slope.