11 November 2016
St-Luc-de-Vincennes: a spectacular quick clay (?) slide in Quebec
Posted by Dave Petley
St-Luc-de-Vincennes: a spectacular quick clay (?) slide in Quebec
A spectacular landslide occurred yesterday (Thursday) morning at the village of St-Luc-de-Vincennes in Quebec, Canada. Reports suggest that an area about 200 m wide was affected, and as a result several houses have had to be evacuated.
The best image of this landslide that I have seen is on Twitter, courtesy of Elizabeth Laplante, a journalist at YVA Nouvelles:-
The landslide at St-Luc-de-Vincennes in Quebec, Canada courtesy of Elizabeth Laplante on Twitter
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That is an impressive slide. Xania News has this less good in terms of resolution but incredibly interesting image too:
The landslide at St-Luc-de-Vincennes in Quebec, Canada via Xania News
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And this is the debris trail, via Mireille Roberge on Twitter:
The debris trail of the landslide at St-Luc-de-Vincennes via Mireille Roberge on Twitter
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The shape of the landslide, with the narrow outlet and large bowl, plus the high mobility of the very wet, muddy debris, suggests to me that this might be a classic quick clay landslide. It would be interesting to know whether works had been undertaken on the slope to cause destabilisation. This is a Google Earth image of the site from 2013:
Google Earth image from 2013 showing the site of the quick clay landslide at St-Luc-de-Vincennes
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There is no sign of instability in the field, but note right at the toe of the failure, where the debris has entered the stream, there is an active landslide in the imagery:
Google Earth image of the toe of St-Luc-de-Vincennes landslide in Quebec
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It is possible that this landslide retrogressed, and then triggered the runaway quick clay (?) landslide.
Previous posts about quick clay landslides
- Possible pre-failure ground deformation at the St-Jude quick clay landslide in Canada
- Possible flowslide (not a sinkhole) in St Jude, Canada
- Norwegian landslide – is this a quick clay slide?
- Vestfold in Norway – an unusual landslide takes out a major highway bridge
- The Rissa landslide – new (old) video available online
Dave Petley is the Vice-Chancellor of the University of Hull in the United Kingdom. His blog provides commentary and analysis of landslide events occurring worldwide, including the landslides themselves, latest research, and conferences and meetings.
According to the authorities, they intervened a few hours prior to the large landslide for a smaller slide on the bank of the river but saw no risk for the inhabitants… In the last few days, this area prone to quick clay landslides had heavy rain. Other quick clay landslides such as Nicolet (1955) and Saint-Jude (2010) are all within 100 km of this one.
It absolutely is a quick clay landslide. The Leda clay (actually a mix of clay fine, clay-size rock flour that settled out in glaciomarine Lake Champlain) is widespread throughout much of southeastern Ontario and southwestern Quebec in the St. Lawrence River valley.
There have been dozens of landslides virtually identical to this one, some causing loss of life. The failure would not necessarily have involved human ground disturbance but a natural slope failure of the bank of the small river which then propagated backwards as a growing series of listric normal faults and slumps.
An oblique view from the north on google earth winter imagery from december 2014 hints at the active history of movements along this section of the river. Quebec should be getting better at predicting greater risk of highly regressive slides using these data – G