Monthly Archives: October 2018

Visit in Taiwan in October 2018

Jaboyedoff was invited to participate to the Technical Exchange Workshop on Large-scale Landslide Prevention and Mitigation (10-12 October 2018) in Taipei organized by Soil and Water Conservation Bureau. His contribution was entitled:

Assessing hazard of large slope mass movements and associated geohazards

This was followed by a two days field trip in central north Taiwan.

It was also the opportunity to present a conference at the Taiwan geological Survey on 9.10.2018:

Why do we need conceptual models for landslides? A point of view!

Coming back from Australia MJ spent two more days (20 and 21 October 2018) on a field trip in Central Taiwan led by Professors C.W. Lin and R.F. Chen. The visits were very interesting. It showed the high activity of landsliding in Taiwan Mountain leading to disasters such as Chi Chi earthquakes (1999) and Morakot Typhoon (2009).

Landslide and mitigation work central north Taiwan.

Toppling indicating a large slope mass movement in central north Taiwan.

3rd Virtual Geosciences Conference

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. 

http://virtualoutcrop.com/vgc2018

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

Inventory of shallow and spontaneous landslides and improvement of the methodology to establish hazard and risk maps for the Canton of Vaud

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

REFERENCES

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

Prof. Chigira visit to Risk-Group (September 2018)

Prof. Chigira stayed at Lausanne in September 2018. The purpose of this collaboration was to compare the deep-seated landslide types between Japan and the Alps. The first two weeks Prof. Chigira was able to familiarize himself with the geology of the Alps with the help of the remarkable Swiss geological maps 1: 25’000, but also and especially thanks to the DEM which reveals the instabilities in a remarkable way. During this period, we had a lot of discussion about the mechanisms of destabilization of the slopes. He was also able to give advice to our PhD students during this period.

We were also able to work on a submitted article that is now published:

Jaboyedoff, M., Chigira, M., Arai, N., Derron, M.-H., Rudaz, B., and Tsou, C.-Y. 2019. Testing a surface area prediction and deposit reconstruction method for a landslide cluster that occurred during Typhoon Talas (Japan), Earth Surf. Dynam., 7, 439-458.

His visit personally pushed me to visit sites that I had not yet been able to study, so we realized 3 field trips.

  • The landslide of Yvorne and Tour d’Aï region
  • Visit of the intability of Moosfluh (Riederalp, VS)
  • Visit of the Simano site (Val di Blennio, TI) and the Bedretto valley

Left: View of a depression at the top of Moosfluh whose origin and still under discussion. Right: Crack showing great rock instability under the tours d’Aï.

But above all it allowed us to continue the collaboration with the Prof. Chigira, who will return in September 2019 to the field in Ticino, where M. Jaboyedoff will work with him.