Landslide in Langtang

Landslide in Langtang Valley, Nepal

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Posted by The Watcher on May 05, 2015 in categories Editors’ picks, Landslide

The small village of Langtang, which was located along a popular trekking route near the base of Mount Langtang, was completely buried by ice and rocks shaken loose by devastating earthquake that struck Nepal on April 25, 2015. At least 200 people died in this disaster. 

The village was located below a very steep ridge and above the ridge there is a glacier towards the north-west and large snow field right above the village, MountainHydrology writes.

“There has been a lot of snow fall this year and at the moment of the earthquake there were considerable amounts of snow at higher altitudes. From a preliminary investigation we think it is most likely that either a snow avalanche from directly north of Langtang village or a debris/ice avalanche from the north-west has caused this disaster.”

These are marked by red arrows in the map:

Image courtesy of MountainHydrology

While cloudy conditions have hampered satellite observations of Nepal since the earthquake, the Operational Land Imager (OLI) on Landsat 8 captured a clear view on April 30, 2015.

A mixture of snow, ice, and debris – which originated in snowfields on the slopes above Langtang – slid toward the Langtang River and buried the village.

Image acquired on April 30, 2015. Credit: USGS/NASA Landsat 8.

Walter Immerzeel and Philip Kraaijenbrink, members of a group of volunteer scientists (Mountain Hydrology) with expertise in remote sensing, were the first to identify and analyze the landslide using Landsat 8.

“The Langtang River was completely covered by the deposit that buried Langtang Village, but there is no evidence yet of a lake forming behind the blockage,” the scientists noted.

This may indicate that the water has found its way through the debris, snow, and ice which is significant because rivers damned with landslide debris can back up and lead to destructive downstream floods if the natural dam fails.

Image credit: Universiteit Utrecht.

• PDF version of this map is available on MountainHydrology as well as KMZ file for interactive data analysis.

A video uploaded by YouTube user Shaky on May 4, 2015 shows the start of the avalanche. Its description says:

“We were somewhere between Godatabela and Langtang. After the quake large boulders destroyed the forest on the opposite side of the river. Then rocks started rolling on our side and finally the huge avalanche and landslide that destroyed Langtang village created a cloud of snow and mud that came over us and covered everything.”

Nepal Earthquake News

The 2015 Nepal earthquake (also known as the Gorkha earthquake), which killed more than 7,000 people and injured more than twice as many, occurred at 11:56 NST on 25 April, with a moment magnitude (Mw) of 7.8Mw or 8.1Ms and a maximum Mercalli Intensity of IX (Violent). Its epicenter was the village of Barpak, Gorkha district, and its hypocenter was at a depth of approximately 15 km (9.3 mi).

It was the most powerful disaster to strike Nepal since the 1934 Nepal-Bihar earthquake. Some casualties were also reported in the adjoining areas of India, China, and Bangladesh.

The earthquake triggered an avalanche on Mount Everest, killing at least 19 making it the deadliest day on the mountain in history. It triggered another huge avalanche in Langtang valley, where 250 were reported missing.

Hundreds of thousands of people were made homeless with entire villages flattened, across many districts of the country. Centuries-old buildings were destroyed at UNESCO World Heritage sites in the Kathmandu Valley, including some at the Kathmandu Durbar Square, the Patan Durbar Square and the Bhaktapur Durbar Square. Geophysicists and other experts had warned for decades that Nepal was vulnerable to a deadly earthquake, particularly because of its geology, urbanization, and architecture.

Continued aftershocks occurred throughout Nepal within 15-20 minute intervals, with one shock reaching a magnitude of 6.7 on 26 April at 12:54:08 NST. The country also had a continued risk of landslides.