18 December 2018

Loch Quoich landslide: an interesting and disruptive failure in the Highlands of Scotland

Posted by Dave Petley

Loch Quoich landslide: an interesting and disruptive failure in the Highlands of Scotland

On 10th November a significant landslide occurred at Loch Quoich near Kinloch Hourn in the Highlands of western Scotland.  The Highland Council has a really good update on this landslide on their webpages, which includes this image:-

Loch Quioch

The landslide at Loch Quoich in the Highlands of Scotland. Image via the Highland Council.

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This landslide, which has a reported mass of about 9,000 tonnes, extends over a distance of about 1 m.  The slip has blocked the road across the slope and also caused operations at the dam to be shut down as a result of debris accumulation in the spillway.  The landslide destroyed a pylon, cutting the electricity supply to 20,000 homes, as well as destroying telephone cables. Services have now been restored, but the road remains closed and will not reopen prior to mid 2019.

The best images of the landslide can be found in a drone video that has been posted online to Vimeo by the power company SSEN.  The quality of the imagery is fantastic.  You may or may not be able to view it below; if not then follow this link:

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This video gives an amazing view of the structure of the landslide.  So, starting from the top, this is the source area:-

Loch Quoich

The source area of the Loch Quoich landslide in Scotland. Still from a drone video posted by SSEN.

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The landslide appears to have initiated through a toppling failure of the rock bluff.  Note the very obvious fault running through the middle of the outcrop.  The initial failure has entrained a large volume of material from the upper part of the slope to generate a substantial failure.  The upper portion of this entrainment zone can be seen below:

Loch Quoich

The entrainment zone of the Loch Quoich landslide in Scotland. Still from a drone video posted by SSEN.

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Further down the slope the mechanism changes to deposition (with some erosion in the channels):-

Loch Quoich

The transition from the entrainment zone to the deposition of the Loch Quoich landslide in Scotland. Still from a drone video posted by SSEN.

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Below this the landslide has deposited a comparatively thin mass over a large area.  Note the destroyed pylon.  It is interesting that the deposit was able to cross the spillway:-

Loch Quoich

The lower part of the of the Loch Quoich landslide in Scotland. Still from a drone video posted by SSEN.

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