21 June 2015

Tbilisi, Georgia:- a landslide dam-break flood killed 19 people

Posted by Dave Petley

Tbilisi flood – 14th June 2015

A week ago, on Sunday 14th June, a flash flood ripped through a part of Tbilisi, the capital city of Georgia, causing a very significant amount of damage:


The floods are known to have killed 19 people and to have injured a further 457 people.  Three people remain missing.  The flood inundated Tbilisi Zoo, killing large numbers of animals and releasing many more:


Earlier this week it was reported that a tiger that escaped from the zoo killed a man before being shot.  Another tiger was thought to be on the on the loose, but I am unsure as to whether it has been recaptured.  News reports also suggest that one of the penguins in the zoo made a bid for freedom.  In an effort that is somewhat reminiscent of a scene from The Great Escape it was finally recaptured 60 km downstream.

Understandably, the flood has been very controversial in Georgia.  Whilst I am not really able to comment on the factors that underlie the event, it is clear that the flood itself was caused by the collapse of a landslide dam created on the Vere River near to the village of Akhaldaba.  The Georgian Government has produced a video animation of the landslide and flood.  Unfortunately due to a hosting problem associated with upgrading the software that hosts this site, I cannot embed videos at present.  However, you can access it via the Youtube website. Although it is not in English, the sequence of events is clear, representing a classic cascading sequence of heavy rainfall, slope failure, valley-blockage, lake formation, dam collapse and catastrophic flood / debris flow.

The landslide is estimated to have had a volume of about 1 million cubic metres.  This still from the video above shows the slide:

Tbilisi landslide.

The landslide appears to be a shallow failure for the post part, possibly with a rotational component in the headscarp area.  There appears to be a lot of water on the shear surface.  Interestingly, Tbilisi also suffered devastating floods on a number of previous occasions, and the zoo has been destroyed by floods on the Vere River at least once before.  It would be interesting to know if these earlier events were also due to landslide dams on the Vere River .