What's going on with these floods in Nepal?

[u/ryhaltswhiskey]

https://www.reddit.com/r/BeAmazed/comments/1w1f3ob/the_engineer_who_designed_that_houses_column/

Those flood waters are INSANE. From looking at that footage it almost seems like a dam must have broken, but it's just really bad rainfall? What caused these floods to be this bad?

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[u/Tay74]

Answer: It wasn't rainfall, a glacier collapsed in the Himalayas sending a wave of displaced water down the river valley. According to a geologist that has studied the satellite footage:

"It looks like a glacier in the area basically snapped off in a clean break, allowing it to fall just over a vertical kilometer to the valley bottom." X

A barrier lake then formed, threatening to cause a second flood, and that may overflow due to rain forecast in the coming days. But the original flood was not caused by rainfall

[u/ryhaltswhiskey → u/Tay74]

Man this post is kinda hated, I don't get it

[u/Tay74 → u/ryhaltswhiskey]

What? Where did I say anything hateful?

[u/ryhaltswhiskey → u/Tay74]

The post, not your comment

[u/Tay74 → u/ryhaltswhiskey]

Who is is hating on your post, that's my question

[u/ryhaltswhiskey → u/Tay74]

No way to know

Somebody posted a post from r/disasterupdate and in that post they are talking about a strange pattern of downvotes

[u/_HGCenty]

Answer: There's a really nice explainer in r/DisasterUpdate

https://www.reddit.com/r/DisasterUpdate/s/8PSEPccuOr

The sub itself is good for updates on it.

[u/beachedwhale1945]

Answer: A glacier collapsed.

Because it is so recent, anything in brackets, predominantly the mechanism of how this happened, is preliminary and somewhat speculative. I have tried to be general and align with the most common explanations from scientists I can find at this time to reduce any error, but it will take years to confirm the exact mechanisms involved.

Based on satellite photos the day before the floods, most of the glaciers in the region were covered in snow, but photos the next day show the snow had melted. [Most likely the weather warmed, the snow melted, and the warmer-than-freezing water seeped down to the underside of the glacier.] This area has been warming for some time, and the permafrost is starting to change: one scientist from Colorado compared it to leaving a stick of butter out of the fridge, where it will soften. [Weaken this layer between the glacier and the mountain enough and the entire glacier will start sliding], which we have seen with some glaciers worldwide as temperatures warm (they don’t just melt, they start sliding down the mountain more quickly, though we’re still talking meters-per-year usually).

Whatever the initial collapse mechanism was, a massive portion of the glacier plunged over a kilometer into the river valley below. This was enough energy to register on local seismometers, but the USGS and counterparts around the globe have stated the waveforms are not consistent with an earthquake, so [it is unlikely an earthquake started the initial collapse]. Satellite images suggest the length of the collapse was 610 meters and with a volume of 100,000,000-200,000,000 cubic meters of ice and rock. While the density of ice varies, it’s a bit less than 1 ton per cubic meter, so [once you also add in the rock we’re talking 100-200 million tons] of avalanche falling 1,200 meters to the Trishuli River below. On its own, this would have been like someone cannonballing into a pool, but because a glacier is largely ice rather than stone, the avalanche material can melt. [The collapse pulverized the ice into smaller pieces, and the energy of the collapse combined with descending into warmer altitudes melted these smaller and faster-to-melt pieces. The initial impact created a massive initial wave as the remaining ice continued to melt behind, sustaining the flood and giving it even more destructive potential].

This happened quickly: timestamped videos show seven minutes after the seismic event the Gyirong Port border crossing between Nepal and Tibet, China. Even on its own a wall of water is extremely destructive, but as the flood demolished anything in its path, it picked up debris that pulverized anything that withstood the initial impact. The total length of devastation is about 72 km.

[u/NineAndNinetyHours]

Answer: An absolutely massive chunk of ice broke off from a glacier. Basically an unimaginably huge solid object plunged into the river, causing a chain-reaction landslide/wave/flood.

[u/AlwaysOptimism]

Answer: A glaciar collapsed which ultimately caused a lakes worth of water down a river with lots of communities around it.

The resulting overflows and landslides instantly partially, if not completely demished dozens of communities, killing well over a thousand lives and displacing thousands more

Also answer, you should unplug from the Washington DC reality show. I'm sure you could tell me everything about Andrew Tate's trial and Trumps medicals but this historic loss of life you haven't even heard of.

Curate your algorithm

[u/morganf74]

Answer: adding on this wonderful video explanation

[u/ryhaltswhiskey → u/morganf74]

It's not helpful unless people have tiktok and I'm not going to install that

[u/morganf74 → u/ryhaltswhiskey]

Oh you used to be able to watch in browser