Melamchi: a landslide dam break flood in Nepal last week

I was away on leave in London last week; as both the South Asia monsoon and the northern hemisphere mountain rockfall season are now underway, there is much to discuss.  So, to start, on 14 June 2021 a large flood struck the Melamchi area of Nepal following an early monsoon downpour.  The flooding caused high levels of damage.  Three people are confirmed to have died, whilst 17 more remain missing.  Many houses were destroyed:-

The aftermath of the Melamchi landslide dam break flood in Nepal. Image from the Kathmandu Post.

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It is now clear that this event resulted from the breach of a landslide dam upstream, releasing a torrential debris flow and flood that struck the settlements.  On Twitter there is a short video that has captured some of the landsliding:

‘पहिरोले थुनिएको खोला फुट्दा मेलम्चीमा बाढी’

– हेलिकोप्टरबाट मेलम्ची क्षेत्र निरीक्षणपछि स्वास्थ्यमन्त्री शेरबहादुर तामाङले भने– हेलम्बु गाउँपालिकाको चोक्पुभन्दा ५०० मिटरमाथि पहिरो गएर खोला थुनिएका कारण मेलम्चीमा बाढी आएको हो ।#Melamchi #Landslide #Flood #nayapatrika pic.twitter.com/GZNwwUjVB2

— Naya Patrika (@NAYA_PATRIKA) June 16, 2021

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The translation of the text is:

‘Melamchi floods due to landslide’ – After inspecting the Melamchi area from a helicopter, Health Minister Sher Bahadur Tamang said that the Melamchi was flooded due to a landslide 500 meters above the Chokpu of Helambu village.

NP News has this graphic of the site:-

Graphic illustrating the landslide at Melamchi in Nepal, created by NP News.

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If this is correct then the location is about 28.109, 85.46, but this is unconfirmed.  Unfortunately there is too much cloud to get a good satellite image.  There are better versions of the inset image on the left above, but these seem to sit on insecure sites so I am not providing a link.  They appear to show a very large, valley blocking landslide just above the area with the white circle on this image above.

There also appears to be substantial damage to the critically important Melamchi Water Supply Project.  I note once again that major infrastructure projects are being built in the Himalayas without a proper understanding of the risks from these devastating landslides, as we noted in our recent paper in Science.

Interestingly, there are also reports of another valley blocking landslide threatening communities in Nepal, this time along the banks of the Tamakoshi River – this valley blocking landslide is in Tibet.  Works are apparently underway to try to unblock the channel.  We will watch with interest to see what happens there.  Thanks to John Reynolds for highlighting this one to me.