Use of LIDAR in landslide investigations: a review

This paper presents a short history of the appraisal of laser scanner technologies in geosciences used for imaging relief by high-resolution digital elevation models (HRDEMs) or 3D models. A general overview of light detection and ranging (LIDAR) techniques applied to landslides is given, followed by a review of different applications of LIDAR for landslide, rockfall and debris-flow. These applications are classified as: (1) Detection and characterization of mass movements; (2) Hazard assessment and susceptibility mapping; (3) Modelling; (4) Monitoring. This review emphasizes how LIDAR-derived HRDEMs can be used to investigate any type of landslides. It is clear that such HRDEMs are not yet a common tool for landslides investigations, but this technique has opened new domains of applications that still have to be develope

Overvåking ved akutte skredhendelser

Statens vegvesen (SVV), Norges vassdrags- og energidirektorat (NVE) og Jernbaneverket (JBV) har, gjennom etatssatsningsprosjektet Naturfare - Infrastruktur, Flom og Skred (NIFS) et delprosjekt (DP4) som omhandler overvåking og varsling av naturfarer. Høsten 2012 vart det utført en øvelse på Sunndalsøra sammen med Åknes/Tafjord Beredskap IKS (ÅTB) og Norges geologiske undersøkelse (NGU). Øvelsens mål var å teste nytten av bakkebasert InSAR (ÅTB) og bakkebasert laserskanning (NGU) ved en akutt steinspranghendelse. Rapporten beskriver hva som ble gjort i forbindelse med øvelsen og hvordan ÅTB og NGU tenker seg at bakkebasert InSAR og laserskanning kan benyttes ved skredhendelser for å dokumentere bevegelse/stabilitet i skredområdet. Rapporten konkluderer med at dette ville være nyttige data for å gjøre en best mulig geologisk analyse av stabilitetssituasjonen. Det kan da inngå i en vurdering om opprettholdelse/avvikling av veistengning, evakuering osv

Evolution of a highly vulnerable ice-cored moraine: Col des Gentianes, Swiss Alps.

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Evolution of a highly vulnerable ice-cored moraine: Col des Gentianes, Swiss Alps.

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Semi-empirical prediction of dam height and stability of dams formed by rock slope failures in Norway

Based on an inventory of 69 dams formed by rock slope failures in southwestern Norway and published inventories from other parts of the world, we developed semi-empirical relationships linking the maximum dam height (HD.max in metres) to dam volume (VD in 106 m3) and other relevant parameters such as valley width (WV in metres) or dam area (AD in square kilometres). Power laws are obtained for HD.max=f(VD) and HD.max=f(VD, WV), while a linear relationship links HD.max to the ratio VD∕AD. For dams in southwestern Norway, the linear relationship HD.max=1.75×VD/AD has the least uncertainties and provides the best results when comparing predicted dam heights with a validation dataset composed of existing dams in northern Norway and numerically modelled dams for possible rock slope failures. To assess the stability of future dams, we use the predicted dam heights in the dimensionless blockage index (DBI) and relating this index to the probability of dam failure derived from our dataset and other published databases on landslide dams. This study underlines the potential of semi-empirical relationships for assessing dam height and stability that needs to be included in preliminary hazard and risk assessment for unstable rock slopes, because damming of a river is an important secondary effect of landslides due to upstream flooding and possible outburst floods in the case of dam failure

Mapping of Unstable and Potentially Unstable Slopes in Sogne og Fjordane

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 app lied 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 out on the slope east of Flåm in the Aurland valley, and results have been reported separately (NGU 20 11 .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. The largest movements with 1.5 cm horizontal and 1.5 cm vertical displacement were measured on the instability with a volume of approx. 1 Mm3 in Ovris valley. Opening of cracks has been measured at that site also in the 1960’s, 1970’s and 1980’s. Our data suggest a slight acceleration of this instability. Acceleration was also documented for a 100.000 m3 large instability called Lifjellet, although velocity of that site is less than half of the velocity of the block in Ovris valley. However at that site a collapse of a rockslope with a volume of 25.000 to 30.000 m3 occurred only 19 years ago. Installation of continuous monitoring and early-warning systems should be considered at both of those sites as well as at similar sites where relatively small instabilities that might fail without a long acceleration phase are positioned above settlements (Gråberget in Høyanger municipality). Similarly all other monitored instabilities in Sogn og Fjordane are in the order of mm/yr and not considered to be critical on a short term. However, periodic monitoring has to be continued. Cosmogenic nuclide dating (CN) has been applied to determine ages of rockslide deposits in Fjærlandfjord (Sogne municipality) and at the slope E of Flåm (Aurland community), resulting in Late Pleistocene and Holocene ages. CN dating has also applied to the sliding planes at Skjeringahaugane (Luste municipality). The results indicate that the movement initiated at the beginning of the Holocene and is progressive. Long term slip rates are in the same order of slip rates measured by dGPS