23 August 2014

Dariali Gorge: another very large landslide from the Devdoraki glacier

Posted by Dave Petley

Dariali Gorge landslide number 2

In May this year a very large landslide occurred at Devdoraki in Georgia, blocking the strategically-important Dariali Gorge.  This transpired to be a large rockslope failure from directly below the glacier, which turned into a high speed, long runout flow.  I was lucky enough to be able to feature some images of the landslide.

On 20th August, another landslide occurred at the same site, once again blocking the Dariali Gorge.  This landslide, which is reported to have originated at the glacier, is reported to have been larger.  The trigger was reportedly heavy rainfall.  The landslide, and the resulting damage, are sufficiently serious to have needed a visit to the site by the President of Georgia.  Two people lost their lives in the landslide, both workers from the nearby HEP project.

There are some images on the internet of the landslide.  The best that I have found are on this Georgian news website.  At times it is not entirely clear what they are showing, but they are interesting nonetheless.  I suspect that these two images show the landslide deposit itself – it appears that the landslide blocked the river, which has then breached the dam to create an outburst flood(?):



An interesting aspect of this is the landslide deposit marks on the valley walls, which suggest that a very substantial volume of material has been eroded away.  It is not clear to me whether this is from the May or the August landslide events.

This image seems to show downstream damage from the outburst flood:



In many ways this image is the most interesting.  It is possible that it shows the channel through which the landslide travelled to reach the Dariali Valley, although this is speculation at best:


It would be fascinating to see a set of images of the source and track of this landslide – to have two very mobile, long runout landslides in the same valley in a short period is both unusual and intriguing.  Does anyone know if such a set of images has been posted online?