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A flood of floods

Saturday, August 2nd, 2014
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As a young cub reporter, I was just starting out in journalism in 1981. This was the time before Twitter and smartphones, and when we heard that there had been a flood on the Bhote Kosi two of us packed our bags and hit the Arniko Highway in our trusty VW Beetle.

We crested the ridge past Dolalghat to be confronted with an angry dark river with ocean-like waves carrying tree trunks and other debris downstream.  We could see the high-water mark on the banks, and knew that the flood had been much higher at night.

By the time we got to Lamosangu and approached the Sun Kosi intake barrage, the road abruptly vanished at almost the exact spot near Jure where Saturday morning’s deadly landslide occurredThe small bazar is now under tons of rocks and mud, the landslide blocked the Bhote Kosi and dammed a lake that stretches 3km upstream.

In 1981, nearly 20 km of the Arniko Highway and all its bridges were washed away, the Sun Kosi power house was seriously damaged and there was loss of life and property all the way down the valley. Everyone thought it was a monsoon flood, but the event was later traced to a glacial lake high up on the northern side of the Himalaya in Tibet. Like other rivers in Nepal, the Bhote Kosi is prone to glacial lake outburst floods, and geologists have found evidence of previous events in 1935 and 1964. 

This time, it was a massive slope failure tumbling down and blocking a major trans-Himalayan river. The landslide started at 3AM on a steep slope about 1,000 m above the river near to where there had been a smaller landslide four years previously. The residents of Jure had no warning and most of them were asleep when the whole side of a mountain fell on their homes. Some 15 injured were rescued, eight bodies have been recovered, but dozens of others are believed to entombed under rock.

Pic: Saroj Dong

Pic: Saroj Dong

The landslide covers a swathe 500m across and filled the river with rocks and mud 100m thick. Such was the energy of the impact, that the landslide scoured a heavily forested slope on the opposite bank. Dust from the pulverised rocks have turned the forest brown right up the mountain on the other side.

A section of the Arniko Highway joining Nepal and China has been destroyed again, transmission lines from the 46MW Bhote Kosi plant has been cut, the powerhouse of the 2MW Sanima project has been submerged.

“I am shocked by the size of the bishyari,” says water expert Dipak Gyawali, using the Nepali term for landslide blockage of a river. “I hope the Nepal Army can release the water before the lake upstream gets any bigger and more dangerous.”

All day Saturday, the government warned citizens downstream to evacuate to higher ground. And there was alert even 250km downstream at the Kosi Barrage and across the border in Bihar. By 2PM, the impounded lake started to find a small channel around the debris, and Nepal Army engineers set off controlled explosions to widen it. As night fell, the water level was down by 2m and falling. Experts, however, warn that there is still a danger that heavy rains in the catchment or erosion of the natural dam could cause overtopping.  There is an estimated 6 million cubic metres of water backed up which could cause catastrophic floods downstream.

International landslide expert Dave Petley of Durham University has researched the Bhote Kosi Valley, and writes in his blog that a major landslide in the area was not a surprise. ‘The images suggest that there is no reason to be confident that the dam will not breach … which could generate a very large flood; when full the effects could be very serious,’ he writes.

Petley advises action on three priority areas: Evacuate people downstream, put a warning system in place, excavate a channel with heavy machinery. The government, police and Nepal Army seem to be following this advice to the letter. An army unit is at the site monitoring the water level overnight, and will widen the channel if levels rise again.

Unlike previous floods where downstream settlements were caught off guard, on Saturday most people knew through mobile phone calls or the radio that the river had been blocked upstream. In some places like Lamosangu there were stampedes in the morning as panic spread.

Saturday’s flood also saw social networking sites breaking the news, posting photographs and videos which the tv channels and others used. Kapil Dhital , an engineer with the Mid-Bhote Kosi Hydropower Project, was the first on twitter (@bewitchkapil) with a post at 5:50 AM from Barabise, saying ‘a whole mountain has fallen into the river, Barabise in danger’. All day, Dhital posted dramatic photographs of the lake level rising and submerging the Sanima powerhouse, and of the landslide debris from various angles:

Bhote Koshi landslide 2

Bhote Koshi landslide 4

Bhote Koshi landslide 5

The most unique photograph is one of the river from above the point where the landslide originated and posted on which shows the width of the river blockage, the scouring on the opposite bank and the lake starting to back up.

Bhote Koshi landslide 1


The crisis is not over on the Bhote Kosi and Sun Kosi Valleys, but it is yet another reminder that Himalayan rivers can be unpredictable due to monsoon floods, landslide and glacial lake outburst floods. Human settlements and infrastructure have to take this risk into account.

Kunda Dixit

Photos from Nepal Army: 

Nepal Army mobilized for rescue operations

Nepal Army mobilized for rescue operations  2

Nepal Army mobilized for rescue operations 3

Nepal Army mobilized for rescue operations 4

Nepal Army mobilized for rescue operations 5

 

 

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