1 March 2016

Darjeeling day 1: Landslides on National Highway 10

Posted by dr-dave

Darjeeling day 1: Landslides on NH10

For five days I am in Darjeeling in northern India on a visit organised under the UKIERI programme. We are staying in Kalimpong, a hill town with a serious landslide problem, working alongside Praful Rao and colleagues of the wonderful Save the Hills NGO.  It has long been an ambition of mine to visit this area, and it is a great pleasure to meet Wing Commander Rao, who has long been a hero of mine.  I can think of no NGO that has done more to raise awareness of landslides in their local area than Save the Hills.

Yesterday (Monday) we drove from Bagdogra Airport up to Kalimpong via National Highway 10.  Along the way were met by the officers from the Border Roads Organisation (BRO), the part of the Indian Army responsible for maintaining the roads in the Himalayas, who were keen to show us a serious landslide problem on this strategically vital highway.  This landslide activated in heavy rainfall in the early part of the 2015 monsoon, and during the major movement period it blocked the highway for five days.  The BRO had a backhoe buried in the landslide, although fortunately the operator escaped uninjured.

This is the landslide as it is now.  As you can see, our visit was in rapidly failing light, sadly.

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Darjeeling landslide

The major landslide on NH10 in Darjeeling, India

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There is clearly a great deal of loose material on the surface of this slide, and the threat that this will pose in the 2016 monsoon in three months is clear. I wonder though if the major issue here may be a deeper seated movement in the block that is directly above the silver car in the image above.  That is the section of the slope shown below.  My view would be that this section of the landslide needs to be monitored to understand what is happening here.

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Darjeeling landslide

Detail of the major landslide on NH10 in Darjeeling, India

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Viewed from the other side, it is also clear that there is another major block on the margin of the existing landslide that is potentially unstable. It appears that a tension crack has opened at the back of the block (note the fresh rock that has been exposed in the upper right portion of the image). Again, it is hard not to believe that this will cause problems in the future:

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Darjeeling landslide

Potential new areas of instability on the flank of the major landslide on NH10 in Darjeeling, India

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