Why did the glaciers collapse and cause devastating flash floods in central Nepal along with the Lhende Khola and Trishuli rivers? The initial reports identified the seismic impact as a 4.4 magnitude earthquake as a primary cause of Nepal's flash floods.
But the US Geological Survey confirmed that roughly 0.2 square kilometers of glacial ice and bedrock broke away at 5200 meters altitude.
The falling mass resulted in flash floods in the Tibet valley. The floodwater created a high velocity surge that rushed 170 kilometers downstream to cause hundreds of fatalities and destroying main border infrastructure between Nepal and Tibet.
Why did the Himalayan Ice Mass Shear Off So Violently?
Planet Labs satellite imagery indicates that the hanging terminus of a glacier located near Langtang Lirung separated from the parent body and fell over 1200 meters down to the valley below.
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Central Nepal Glacier Collapse Parameter
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Official Data Point
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Initial Collapse Altitude
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5 200 meters
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Vertical Fall Distance
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About 1.2 kilometers
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Seismic Signal Equivalence
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5.2 magnitude event (USGS)
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Water Level Rise Rate
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Up to 9 meters in 30 minutes
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Primary River Corridors
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Lhende Khola,
Bhote Koshi,
Trishuli
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But it did not take long for the barrier created by the fallen debris to be breached. And when this happened, a wave of mud and rocks was unleashed which razed multi storied buildings and demolished the Gyirong Port border crossing.
How Climate Change Increases High Altitude Flash Floods
Temperatures across the Hindu Kush Himalaya are rising twice as fast as the global average. This accelerated warming degrades high-altitude permafrost. The natural glue holding mountain rock faces and heavy glaciers together.
UN environmental reports indicate Nepal has lost nearly one-third of its total glacial ice volume over the past thirty years.
When these high altitude ice shelves collapse they release trapped meltwater and scour riverbeds.
The melted water generates dense debris torrents with the destructive density of liquid concrete.
Which Areas Face Ongoing Flood Threat During Emergency Operations?
Search teams face major hurdles clearing thick mud and restoring severed communications in the Rasuwa and Nuwakot districts.
There is a new barrier lake located on the Nepal and China borders that has grown to more than 2.5 million cubic meters, resulting in an emergency warning of floods. People living near the River Trishuli and River Narayani are advised to be highly vigilant.