François Noël, Teresa Gracchi and Emmanuel Wyser of the Risk Analysis Group (UNIL) went to Barcelonnette (France) from the 23rd to the 27th of September for an amazing experimental work in the field dealing with rock fall trajectories and associated topics (e.g. impact response, energy transfer, etc.), amongst other French researchers from Active Deformation Group of the University of Strasbourg (EOST, leaded by Jean-Philippe Malet) and the IRSTEA Institute of Grenoble (leaded by Franck Bourrier).
Several (30) rocks were thrown down into a short but steep gully while seismic signals (EOST) and high-speed imaging (IRSTEA & UNIL) were acquired. High resolution 3D imagings were acquired thanks to TLS and SfM.
Accelerometers (ISTE & EOST) were also included in few rocky blocks to monitor and acquire data to better understand impact response, angular velocity changes and other exciting data.
The 3rd Virtual Geosciences Conference took place in Kingston (Ontario) on 22-24 August 2018. This conference is at the intersection of geomatics, visualization, computer vision, graphics and gaming, as well as virtual and augmented reality with applications to a range of geoscience subfields, such as geological mapping, geomorphology, geohazards, glaciology, volcanology, tunnelling, and mining. It was organized at Queen’s University, by Ryan Kromer, a former PhD student of Lausanne and Queen’s universities.
MH Derron, S. Buckley, J. Chandler, M. Jaboyedoff and R. Kromer (Chairman of the 3rd VGC)
The first VGC conference was in Lausanne in 2014 and then in Bergen in 2016. These events are fantastic opportunities to learn how new technologies can be used in geosciences, gathering together people from different horizons.
Optimizing the use of 3D point clouds data for a better analysis and communication of 3D results. François Noël, Marc-Henri Derron, Michel Jaboyedoff, Catherine Cloutier Jacques Locat Infrared Thermal Imaging for Rock Slope Investigation – Potential and Issues. Marc-Henri Derron, Antoine Guérin, Michel Jaboyedoff
On contrary to hazards which have defined return time for establishing natural hazard maps (for example rock falls or floods), there is no similar methodology for shallow and spontaneous landslides. One way to improve the current methodology is proposed by Cedric Meier, Marc-Henri Derron, Michel Jaboyedoff from RISK-UNIL and Christian Gerber, Veronica Artigue and Melanie Pigeon from the Vaud county administration. It includes the definition of 7 pilots zones based in Jura, Plateau and Alps, on riverbanks or mountain slopes. Based on the new airborne LiDAR acquisition, a former inventory from 1889 to 2013 and basics documents such as geological and topographical maps, air photos, about 110 landslides were registered.
Shallow landslide in the area of Ollon in 2018
The parameters of the source zone of the landslide, like length, width, estimated depth, area, slope angle and propagation angle (Farböschung) were recorded. For each landslide, 3 different volumes (with half-ellipsoid method, elliptical paraboloid method and Sloping Local Base Level or SLBL method, method developed and applied currently at the Institute of Earth Sciences, ISTE – UNIL) were calculated. A volume-frequency distribution, approximated by the Power Law site specific, but also depending on the slope type was developed. Figures showing the probability of the estimated depth or the volume depending on the area of the source zone were also prepared. For the propagation, only 4 % of the landslide have a propagation angle greater than 13°.
Probability of max depth in function of the surface area of the landslide
Jaboyedoff M., & Derron M.-H. 2005: A new method to estimate the infilling of alluvial sediment of glacial valleys using a Sloping Local Base Level, Geogr.Fis.Dinam. Quat., 28, 37-46. VD (2017) : http://www.geo.vd.ch/theme/dangers_nat_thm
The field trip on gravitational slope movements for master students took place for the fifth year at Barcelonnette (French Southern Alps) at the beginning of June. During two weeks, the students had the opportunity to study the landslide of Lavalette, rockfalls around Meolans and debris flows in the Riou Bourdoux catchment. The quite intensive program was composed of mapping and terrestrial LiDAR in the field during day times, data analysis and numerical modelling the evening.
Once again we benefited from all the facilities provided by the Seolane center (center dedicated to host scientific stays at Barcelonnette), and we had the opportunity of a visit guided by Hugo Collomb of the French Office of Forest (ONF-RTM).
The field trip for bachelor students in environment took place at Les Diablerets mountain village in the Swiss Alps during the first week of May. The nearby Pont Bourquin landslide was the main object of study for 32 students during 3 days. Mapping, volumes and risks estimations were at the program.
The Risk Group participated in the European Geosciences Union (EGU) General Assembly in Vienna, Austria, on 08 April to 13 April 2018. This meeting was a great success, with 4,776 oral, 11,128 posters, and 1,419 PICO presentations. 15,075 scientists from 106 countries participated.
As usual, attending The European Geosciences Union (EGU) General Assembly in Vienna is an amazing opportunity for our group to be an interactive part with the huge platform of experts and scientific researchers from over the world and from different fields. The Risk Group people presented 10 contributions as first authors whose titles are below.
Optimizing rockfall simulations by combining high-resolution gridded digital terrain models with 3D point clouds. François Noël et al.
Using average velocities of deep-seated landslides to develop intensity-frequency scenarios. Michel Jaboyedoff et al.
Coupling 3D rockfall propagation to the spatio-temporal frequency for a realistic rockfall hazard mapping. Cécile D’Almeida et al.
SFM photogrammetry for rockfall hazard evaluation in a zero data site (acase study of a touristic area of northern Tunisia). Mariam Ben Hammouda et al.
Urbanized areas, natural hazard and risk in Rwanda. Emmanuel Nduwayezu et al.
Axisymmetric granular collapse: underlying invariance of granular dynamic? Emmanuel Wyser et al.
Inventory of shallow landslides in regard with their frequency in the Canton of Vaud (Switzerland). Cedric Meier et al.
Finding the best locations of monitoring devices based on visibility analysis with 3D point clouds. Teresa Gracchi et al.
Practical application of an open-source, web-GIS platform (RISKGIS) in learning risk management of geohazards. Zar Chi Aye et al
Assessment of potential pollution of an unconfined aquifer in Abidjan by hydrocarbons. Amenan Agnès Kouamé et al.
The Journées de la Géologie Tunisienne was organized by the office national des mines in Hammamet from 23 to 25 March. This year, this conference was dedicated to the mapping of georisks. Mariam Ben Hammouda and Marc-Henri Derron from the group Risk took part to this conference, presenting advances in point cloud processing. It was also the opportunity to visit the Cap Bon area where Mariam is doing her PhD thesis.
Beginning of March was a great opportunity for Marc-Henri Derron to visit sites and colleagues in Taiwan for the first time. Invited by Prof. C.W. Lin (National Cheng Kun Univ. in Tainan) and Prof. R.F. Chen (Chinese Culture Univ. in Taipei), Marc-Henri had the opportunity to visit large landslides in central Taiwan, as well as giving 3 presentations on various aspect of landslide investigation techniques.
Slope conditions, steep and weathered, are drastically different from those encountered in the Alps. This visit was the first one for a group Risk’s member and we are confident it will lead to further cooperation.
The Risk group participed in a study conducted by researchers at the University of Lausanne whose results where published in Nature Plants . Results reveal that the genome of oak Napoleon has evolved little during its first 234 years of existence.
The 3D modelling was carry out using a LiDAR. Terrestrial LiDAR scans were taken around the oak every 60°. The six scans were cleaned from background objects and aligned in order to generate a 1.2 million 3D-points cloud. The mesh from the 3D points cloud was colourized to produce the final 3D oak model.
The Risk Analysis Group (C. d’Almeida, F.Noël) spent a week in the principality of Andorra to carry out lidar survey. The city of Andorra-la-Vella, located in the hearth of the Pyrenees is a very dense city surrounded by landslides and active cliffs.
Lidar and photographs survey of 12 sites were performed. These sites were previously monitored by the Risk Analysis Group (Antonio Abellan) in 2009 and 2012. Exploiting the lidar scans will permit to quantify the erosion activity of the cliffs and detect potential instabilities. The Risk Analysis Group thanks the geo-hazard expert Joan Torrebadella from Georisk-international for his warm welcome, and accompanying during this week.