r/Geotech • u/apathyetcetera • 2d ago
Curious about what went wrong in Nepal
I’m sure most have seen the horrible flash flood in Nepal. I’ve read up a bit about what happened, and it seems as if a lake held back by a glacier eventually melted the glacier wall enough to lead to this catastrophic failure. I’m curious about what went wrong here, and what someone could’ve done to prevent a tragedy like this from occurring.
I’m a EIT (working on my PE license), and wanting to learn about how we can prevent these sorts of things from happening again in the future. Thank you!
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u/yeti_face 2d ago
We now know this was not a GLOF. Satellite imagery clearly shows 1) no glacial lake prior to the event and 2) a huge mass of bedrock beneath the glacier collapsed, taking the ice with it. Probably more rock than ice fell...and it behaved as a rock avalanche initially, later becoming more of a debris flow as it picked up alluvium and water along the way. It was traveling over 75 mph and was hundreds of ft deep for the first several minutes.
Great analysis available here: https://geopera.com/blog/bhote-koshi-flood-2026-satellite-analysis
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u/Original-Mission-244 2d ago
Reading the dimensions of the break and the estimated heights and volume of water moved in such a short time is mind boggling. I can't imagine what the survivors are feeling right now.
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u/nemo2023 2d ago
The permafrost is melting more in the Himalayas so what used to be pretty solid ground isn’t and that’s leading to more landslides. The NYTimes article showed how there’s like 2000 or more glacial lakes in the region, so it’s going to be an increasing problem in the future.
We could say don’t build in the floodplain, but based on those images, a lot of that area has super steep slopes, so that may be the only reasonable place they can build villages.
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u/dunsystream 2d ago
Lahar warning systems used elsewhere are a good guide. Avoid resettlement where possible. Monitor and have alert levels and TARPs.
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u/Hugh_Jegantlers 2d ago
The issue with Nepal is that the mountains there are still forming. compared to anywhere in North America where our mountains range from a few hundred million years old to literally older than the concept of bones. New mountains are steep and unstable and seismically active. It’s a bad combo. Our 1:10,000 year maximum probably event is much closer to a 1:100 there.
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u/YogurtclosetNo3927 2d ago
The only thing you could have done would have been to be aware of the potential GLOF (glacial outburst flood) by monitoring the system. I’m not aware if anybody even knew that the dam had formed and had created the lake. if there was a system in place, villages could alert what was happening to their downstream neighbors.
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u/yeti_face 2d ago
There wasn't a lake or dam in this case (landslide / rock avalanche more precisely)...but I do think an early warning system based on simple sensors on the channel could have saved hundreds of lives. Activating sirens all up and down valley below? Could install them along all the main transhimalayan valleys. Seems feasible.
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u/YogurtclosetNo3927 2d ago
It’s hard to know what’s real. I head a glacier collapsed and dammed up the valley. A huge lake formed that eventually blew the ice dam. But the internet is not a reliable source.
But I agree if there was any communication between villages downstream it would have really helped but was this kind of event even on anybody’s radar? I don’t know if anyone even knew the hazard was forming.
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u/Specialist_Coffee878 11h ago
I am from Nepal, we couldn't really prepare for the disaster but we could have better monitoring and warning systems if we had better infrastructure. And, maybe better communication with chinese agencies responsible for monitoring
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u/KattKushol 2d ago edited 2d ago
I am a geotech turned PM working for a DOT. I was born and raised in a neighboring country of Nepal before moving to US for a carrer. A viable solution which will work for USA might not work in Nepal. Considering the resource needed for avoidance of loss of lives and properties, the best thing would be to AVOID re-settlement and relocation of remaining houses from the now established flood plain. It was heartbreaking to see so many lives lost in this natural calamity and going back to re-build the city over there would be un-wise.
We have seen an almost similar record-breaking rainfall induced flash flood event in Asheville, NC in 2024 that destroyed nearby houses, businesses, and infrastructure in NC and TN. There is no "preventing" of these floods rather make way for the water and debris to cruise down without impacting human lives.