26 May 2015
Kali Gandaki: an interesting landslide dam and breach
Early on Sunday a landslide occurred at Ranche in Myagdi District of Nepal, blocking the large Kali Gandaki river. The area affected by the landslide was affected by the earthquake of exactly a month ago, but interestingly there appears to have been no trigger. In this case the response of the authorities appears to have been exemplary, with downstream settlements, most notably the town of Beni, being evacuated and an assessment team being flown by helicopter to the site. The dam breached about 15 hours later, releasing a significant flood that caused damage but no loss of life.
The best source of information throughout was the twitter account of @gocoolchhetri, even though it is in Nepali (and Google translate does not do a good job on Nepali to English). But from the start he tweeted a series of photographs of the blockage on the Kali Gandaki, including this one of the landslide dam itself:
Note the large amounts of dust from ongoing landslide activity. This one showed the lake as it filled:
This one showed the top pf the landslide dam as the water level rose. Note the fine grained material mantling the top of the blockage:
And the dam from above:
And then the overtopping initiating:
And then developing rapidly:
Ekantipur has an article today on the aftermath of the landslide, which states that:
A 2km long and 100 metre deep lake was formed after the landslide dammed the river. The site is about 9km north of Beni, the district headquarters of Myagdi. Massive rocks started falling past Saturday midnight, damaging 27 houses in Bhagawati and Ramche VDCs. Bhimsen KC, a local of the landslide-buried Baisari, said the dam is about 40 metres high from the riverbed. He believes there is no possibility of an outburst of the lake as the dam is about 100 metres wide.
And it includes this image of the aftermath of the landslide that blocked the Kali Gandaki:
This interesting event serves once again to highlight the challenges that face Nepal in the months ahead.