delprosjekt 4 overvåkning og varsling

NIFS-programmet har vært en felles satsing mellom Jernbaneverket, Norges vassdrags- og energi­direktorat og Statens vegvesen. Etatene har store felles utfordringer, og et godt samarbeid er kostnadseffektivt og kompetanseoppbyggende for organisasjonene. Programmet er gjennomført i perioden 2012–2015, med sluttseminar i april 2016. NIFS har hatt som mål å utvikle kunnskap og gode, effektive og fremtidsrettede løsninger for å håndtere ulike naturfarer og bidra til økt samfunnssikkerhet. Gjennom FoU-programmet er det utredet og doku­mentert ulike problemstillinger knyttet til flom og skred. Resultatene har verdi for utøvelse av etatenes samfunnsoppdrag. Implementering av resultat og konkrete anbefalinger tilligger de respektive etatene.Fem testområder er målt gjentatte ganger med bakkebasert laserscanner for å avdekke terrengendringer, og for å illustrere metodens bruksområder. I prosjektet er det avdekt steinsprang, løsmasseskred og deformasjoner av større fjellparti. Rapporten belyser bakkebasert laserscanning som en mangesidig metode for skredovervåking og metodens fordeler og begrensninger kommer godt fre

Guidelines for the selection of appropriate remote sensing technologies for landslide detection, monitoring and rapid mapping: the experience of the SafeLand European Project.

New earth observation satellites, innovative airborne platforms and sensors, high precision laser scanners, and enhanced ground-based geophysical investigation tools are a few examples of the increasing diversity of remote sensing technologies used in landslide analysis. The use of advanced sensors and analysis methods can help to significantly increase our understanding of potentially hazardous areas and helps to reduce associated risk. However, the choice of the optimal technology, analysis method and observation strategy requires careful considerations of the landslide process in the local and regional context, and the advantages and limitations of each technique. Guidelines for the selection of the most suitable remote sensing technologies according to different landslide types, displacement velocities, observational scales and risk management strategies have been proposed. The guidelines are meant to aid operational decision making, and include information such as spatial resolution and coverage, data and processing costs, and maturity of the method. The guidelines target scientists and end-users in charge of risk management, from the detection to the monitoring and the rapid mapping of landslides. They are illustrated by recent innovative methodologies developed for the creation and updating of landslide inventory maps, for the construction of landslide deformation maps and for the quantification of hazard. The guidelines were compiled with contributions from experts on landslide remote sensing from 13 European institutions coming from 8 different countries. This work is presented within the framework of the SafeLand project funded by the European Commission’s FP7 Programme.JRC.H.7-Climate Risk Managemen

Automatic Mapping of Discontinuity Persistence on Rock Masses Using 3D Point Clouds

Finding new ways to quantify discontinuity persistence values in rock masses in an automatic or semi-automatic manner is a considerable challenge, as an alternative to the use of traditional methods based on measuring patches or traces with tapes. Remote sensing techniques potentially provide new ways of analysing visible data from the rock mass. This work presents a methodology for the automatic mapping of discontinuity persistence on rock masses, using 3D point clouds. The method proposed herein starts by clustering points that belong to patches of a given discontinuity. Coplanar clusters are then merged into a single group of points. Persistence is measured in the directions of the dip and strike for each coplanar set of points, resulting in the extraction of the length of the maximum chord and the area of the convex hull. The proposed approach is implemented in a graphic interface with open source software. Three case studies are utilized to illustrate the methodology: (1) small-scale laboratory setup consisting of a regular distribution of cubes with similar dimensions, (2) more complex geometry consisting of a real rock mass surface in an excavated cavern and (3) slope with persistent sub-vertical discontinuities. Results presented good agreement with field measurements, validating the methodology. Complexities and difficulties related to the method (e.g. natural discontinuity waviness) are reported and discussed. An assessment on the applicability of the method to the 3D point cloud is also presented. Utilization of remote sensing data for a more objective characterization of the persistence of planar discontinuities affecting rock masses is highlighted herein

Characterization and monitoring of the Åknes landslide using terrestrial laser scanning

Terrestrial laser scanning (TLS) provides high-resolution point clouds of the topography and new TLS instruments with ranges exceeding 300 m or even 1000 m are powerful tools for characterizing and monitoring slope movements. This study focuses on the 35 million m3 Åknes rockslide in Western Norway, which is one of the most investigated and monitored rockslides in the world. The TLS point clouds are used for the structural analysis of the steep, inaccessible main scarp of the rockslide, including an assessment of the discontinuity sets and fold axes. TLS acquisitions in 2006, 2007 and 2008 provide information on 3-D displacements for the entire scanned area and are not restricted like conventional survey instruments to single measurement points. The affine transformation matrix between two TLS acquisitions precisely describes the rockslide displacements and enables their separation into translational components, such as the displacement velocity and direction, and rotational components, like toppling. This study shows the ability of TLS to obtain reliable 3-D displacement information over a large, unstable area. Finally, a possible instability model for the upper part of Åknes rockslide explains the measured translational and rotational displacements by a combination of southward planar sliding along the gneiss foliation, gravitational vertical settlement along the complex, stepped basal sliding surface and northward toppling toward the opened graben structure

Terrestrial Lidar investigation of the 2004 rockslide along Petit Champlain Street, Québec City (Quebec, Canada)

Au cours des 240 dernières années, 53 mouvements de versant se sont produits le long du promontoire de Québec, causant la mort de 88 personnes principalement lors de chutes de blocs. En octobre 2004, un petit éboulement a atteint la route dans une zone proche de l'éboulement de 1889 qui a tué 35 personnes et blessé 30 autres. Une image 3D a été créée par l'utilisation d'un scanner Lidar terrestre (SLT). Les sept familles de joints identifiées sont en accord avec les mesures effectuées dans de précédentes études. L'imagerie SLT a aussi permit d'estimer les volumes des instabilités passées et d'en analyser le mécanisme : un glissement rocheux qui affecte des blocs débités en parallélépipèdes par d'autres familles de joints. De plus la zone étudiée montre qu'elle est favorable aux chutes de blocs

Detection of millimetric deformation using a terrestrial laser scanner: experiment and application to a rockfall event

Terrestrial laser scanning (TLS) is one of the most promising surveying techniques for rockslope characterization and monitoring. Landslide and rockfall movements can be detected by means of comparison of sequential scans. One of the most pressing challenges of natural hazards is combined temporal and spatial prediction of rockfall. An outdoor experiment was performed to ascertain whether the TLS instrumental error is small enough to enable detection of precursory displacements of millimetric magnitude. This consists of a known displacement of three objects relative to a stable surface. Results show that millimetric changes cannot be detected by the analysis of the unprocessed datasets. Displacement measurement are improved considerably by applying Nearest Neighbour (NN) averaging, which reduces the error (1¿) up to a factor of 6. This technique was applied to displacements prior to the April 2007 rockfall event at Castellfollit de la Roca, Spain. The maximum precursory displacement measured was 45 mm, approximately 2.5 times the standard deviation of the model comparison, hampering the distinction between actual displacement and instrumental error using conventional methodologies. Encouragingly, the precursory displacement was clearly detected by applying the NN averaging method. These results show that millimetric displacements prior to failure can be detected using TLS