13 August 2016

Dzongu: a worrying valley blocking landslide in Sikkim, India

Posted by dr-dave

Dzongu landslide, Sikkim

News has emerged in the last 24 hours of a major valley-blocking landslide at Dzongu in Sikkim, northern India.  The every-impressive and wonderful Save the Hills blog has a series of reports and images.  I won’t seek to replicate them here.  There is some confusion about the timing of the landslide, with suggestions that it occurred on 2nd August.  The landslide, which is large, has blocked the Kanaka River completely, and a lake has started to build behind it.

Suvrat Kar pointed out this Youtube video of the dust cloud generated by the landslide:

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These images, from Save the Hills, show the situation.  This is the landslide scar:

Dzongu landslide

The Dzongu landslide in Sikkim, via Save the Hills

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And this image shows the barrier lake that has developed:

Dzongu landslide

The barrier lake behind the Dzongu landslide, via Save the Hills

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The I Love Siliguri Twitter account has posted this image of the lower reaches of the landslide, which gives an idea of the scale of the mass:

Dzongu landslide

The lower part of the Dzongu landslide, via I love Siliguri twitter account

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Whilst the Darjeeling Chronicle has this before and after image of the river (I have some doubts as this is quiet all it seems, but replicate it here for imformation):

Dzongu Landslide

The dried up Kanaka River downstream of the Dzongu landslide, via the Dareeling Chronicle

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This is the site of the landslide, via Google Earth:

Dzongu landslide

A Google Earth image of the site of the Dzongu landslide in Sikkim

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If this is correct then that vertical extent of the landslide is about 900 metres. Suggestions are that the landslide dam is about 50 m high.

It is really hard to analyse the potential risk from this landslide dam without more information.  I hope that there is a rapid assessment underway.  In the meantime, there is the potential for a damaging outburst flood, meaning that communities downstream need to be extremely vigilant.