r/CatastrophicFailure • u/Economy-Physics2358 • 5d ago
Natural Disaster Flash flood in Nepal on 11 October 2026
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u/3bugsdad 5d ago
Judging by how steep the terrain is and how wide the valley floor, I imagine these types of inundations are more common than we are used to seeing.
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u/tommyk1210 4d ago
Yes, this is absolutely awful for the people that live there.
But if you look at the river bed, there’s a very wide basin of silt there. The river, presumably, regularly reaches that width and flow on a regular basis.
I’m guessing we (people outside Nepal) just see it more now due to social media and the recent disaster there
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u/daiwilly 4d ago
Not really . Why would these people build so close if it happens regularly? it may happen on a small scale but these are catastrophic flows.
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u/PM_ME_FIRE_PICS 3d ago
“Regularly” relative to geologic time scales. Humans have terrible memories and forget quickly. If we did base decisions off of weather events on a geologic time scale, why would anyone ever choose to live in a mobile home in Miami after Hurricane Andrew in 1992 ever again? Yet, there are loads of trailer parks in South Florida.
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u/daiwilly 3d ago
My point being that if this was the same valley as the last one, these buildings below would not exist.
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u/PM_ME_FIRE_PICS 3d ago
This is not the same exact valley as the one in August. Nepal has thousands of valleys like this, and nearly all of them are susceptible to potential mudslides.
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u/sylvyrfyre 5d ago
To be honest, it looks more like mostly a mud and rock flow, mixed with water
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u/AI_moderated_failure 5d ago
Because it was triggered by a landslide not rainfall. It is mostly rock debris.
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u/Phyllostchys 5d ago
This is entirely climate change related. The mountains were previously frozen and they're begging to thaw, which is causing dams and structures to break apart.
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u/Fullertons 4d ago
In this case, it looks like a temporary dam was created and then breached. You can see that the river is typically much much wider.
I bet this was typically a wide, relatively lazy river that turned into this because of a temporary damn breaching. If my assumption is correct, the locals hopefully had plenty of warning to leave and move to high ground.
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u/ahorrribledrummer 4d ago
The riverbed this flash flood is flowing through has shown clear evidence of previous flooding on this exact same scale.
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u/mrb1ll 4d ago
Which dams are you referring to, that have failed due to thawing ground?
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u/timothy53 5d ago
How does this much water just show up
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u/sterrre 5d ago edited 5d ago
As a glacier melts the water can get trapped on top creating a glacial lake that's held in place by a ice dam.
As the glacier melts more and more the lake becomes deeper and the ice dam becomes weaker, eventually it bursts into a glacial outbreak flood.
That's what caused the last flood, not sure if the cause is the same here.
Some extra examples of ancient glacial floods
If you look at the geography of the PNW in the US the entire region was shaped by a series of massive glacial outbreak floods at the end of the last ice age, the Missoula floods which Indian tribes in the area like, the Kalapuya, have kept in their oral memories for thousands of years.
The lakes were in Montana and Idaho when they burst, they scoured the scablands of eastern Washington and carried all the sediment through the gorge to where the flood stalled in the Willamette valley, they then deposited their sediment in the valley and slowly drained out through the mouth of the Columbia river. This happened multiple times as the ice age glaciers melted
As a result native peoples of Oregon became mound builders, they built huge mounds in the center of the valley where they would habitually live at every year. They were still semi-nomadic.
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u/No_Grass6654 4d ago
Actually the last one was not a glacial damn failure. It turned out to be a landslide that took some glacial ice with it and the landslide caused an earthquake.
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u/cheezecake2000 5d ago
Plus they used to think it was just one large flood in the early 1900's but they later found evidence of maybe 30-100 massive floods over a few thousand year span.
Also not very frequent on human time scale, especially if old age was lower 2000 years ago. Only every 30-40 years the damn would burst. Though the amount of floods and scale and exact source are still debated over today most agree it was ice dams somewhere in Montana region and more then one single event.
Been all over Washington seeing the scablands and after I visited Montana you can really see how all that water could fill up Montana's mountain/valley terrain.
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u/Hello_Hangnail 4d ago
I hope I'm dead when our glaciers start melting to the point where they're causing massive inundations like the missoula floods. When the water is coming so hard and so fast that it busted holes through mountains and washed them partially away does not sound like a good time to live through
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u/cheezecake2000 4d ago
No doubt current glaciers will cause problems. We see some flash flooding in Nepal(i think there)from ice melt but lake Missoula was on a scale that is hard to fathom. One that might be able to be replicated with current ice levels. It was near the end of an ice age where over a mile thick sheet of ice covered a huge area of north US and most of Canada.
Dry falls, largest waterfall on earth (though dry now) had ~a 30 story building tall, wall of water flowing over it. Niagara falls is only a few ft thick of water at the edge, if that.
Have you ever seen ripples in sand after a wave passes or in the sand on the side of a road where water flows? There are the same ripples but we thought they were just plains of rolling hills we carved roads through until we got to see them from above.
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u/Traditional_Trust_93 4d ago
Simple explanation: Landslide block river make dam. Dam break from water accumulation, water do this. Thus why the river seems to be lower than it should. All of the dark color in the valley is the normal water level.
This is unrelated to the other one that was real bad at the China/Tibet border. Was landslide with glacier incorporated. Landslide moves down mountain valley and accumulates more stuff. Becomes mudslide/flash flood thing further downriver.
Some geologist videos on the big border crossing one for reference.
How Did the Flood get so big + Talking about border port vid
https://youtu.be/bcNDKu8kuQ0
Discussing the Glacial Lake Question/Theory
https://youtu.be/jsm8o5Wi7Xo
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u/Formal-Fox-7605 4d ago
I know it looks bad, but the fact is that this happens often. The terrain itself tells you that.
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u/Deposto 5d ago
Another one?! Or it's just a dumb clickbait?
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u/Lonely_ProdiG 5d ago
It’s another one.
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u/hettuklaeddi 4d ago
the other one was a different location
it also looks like it wasn’t the first one here, the banks were already pretty wide
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u/AI_moderated_failure 5d ago
This is seperate to the much bigger glacial lake outburst that occurred a month ago. This one is triggered by a landslide. It's a different set of valleys than the ones scoured by the glacial flood.
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u/GoldMountain5 4d ago
Although, This area has very clearly experienced a flash flood just prior to this one based on the amount of erosion present.
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u/AI_moderated_failure 4d ago
I'm no expert on Nepali erosion but from what I gathered during analysis of the glacial outflow that's expected. They get seasonal flash floods, not normally as deadly as this and never as deadly as the previous one, but that would mean erosion like this is fairly common especially in an area that also sees a lot of earthquakes.
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u/sylvyrfyre 5d ago
Yes, another one; genuine footage, different river valley; l guess it happens all the time up there, it's just that we're more aware of it because of the recent cataclysm
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u/WilliamJamesMyers 5d ago
is the takeaway do not live close to a river in Nepal? all low level shit gets wiped out...
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u/chrisk114 4d ago
This looks more like a landslide resulting from the diminishing ice packs further up the mountains
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u/CreativeAdeptness477 5d ago
Repost! This happened a couple of weeks ago... what? What, ANOTHER ONE?! Yikes!
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u/lemonchickentellya 5d ago
People gotta learn to build upland.
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u/goingApeShit_ 5d ago
Nepal cannot catch a break. If I lived Riverside, I’d be moving my house on the hillside. And hoping was on stable ground and not a future landslide location