Southannan: a major railway landslide in Scotland

The United Kingdom has seen a prolonged period of heavy rainfall and, at times, snowfall in recent weeks.  This has led to reports of landslides from around the country, including substantial numbers on coastal cliffs.  Perhaps the most significant event however has happened close to Southannan in Ayrshire, in SW Scotland.  This landslide, and another smaller event, have affected the railway line between Ardrossan and Largs.

Network Rail Scotland has tweeted out an image that provides a really good overview of the landslide:-

The landslide at Southannan in SW Scotland. Image tweeted by Network Rail Scotland.

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This is a classic translational slope failure, with a failure plain that is quite deep, in weathered soil and regolith.  It has reportedly blocked the line for a distance of about 50 metres.  Note the large amounts of water on the surface of the landslide.  I’m also interested by the surface water at the crown of the slide.  It appears that water has flowed down the track from the top of the image, and there is then a puddle right at the head of the landslide (alongside some inquisitive sheep).  Is it possible that water was being fed into the slope at this point, triggering the failure?

The Largs and Millport Weekly News website has a report about this landslide.

The other landslide has occurred on a slope below the railway line.  There is a video in a tweet by Network Rail Scotland:-

This is the other landslip we're dealing with, between Ardrossan and West Kilbride. You can see the signalling cable and the troughing which normally holds it suspended in the air.

We'll be speaking to the team who'll reopen the railway again at lunchtime for an update. pic.twitter.com/MAN8cgHBLz

— Network Rail Scotland (@NetworkRailSCOT) February 8, 2021

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Whilst the track itself has not been lost so far, the signalling cable is damaged and of course there is the possibility of retrogression.

The landslide at Southannan, and the second event shown above, are fixable of course, but they will represent large pieces of work.  I would expect that the railway line will be closed for some time.