Near Juneau, Alaska, USA, the Mendenhall glacier has repeatedly, over the last few years, had a Glacial Lake Outburst Flood. Not nearly as catastrophic as the one in Nepal but it did flood areas near Mendenhall River in Juneau. The latest event was August 13, 2026.
I don't think I've seen a snuff film of that scale before. I'm not good with even fictional horror. This may haunt my dreams. For most of the people there was just nothing they could do. But others would have had a chance if they had run perpendicular to the flow and climbed like their life depended on it. I'll try to remember that the next time I'm fleeing in panic from a flash flood.
Looks like a warning siren could have saved some lives. But apparently this was a black swan.
What is your definition of black swan? This paper is from 2022 and scientists have been warning about climate change for decades. It's not like this possibility wasn't anticipated. It seems likely we'll see more glacial events as the atmosphere warms.
There have been maybe three such events in the 21st century (glacier or landslides producing more than a magnitude 5 quake), and none of them have happened in an area like the Himalayas. The other two were in Alaska on Mt Steller in 2005 and the Lamplugh Glacier in 2016, neither of which produced massive downstream floods.
It usually takes entire icebergs calving off to produce such seismic events and intense monsoons to create such flooding.
A black swan event is an event that is unpredictable because it is so rare.
While I'd wait for confirmation about the cause of this specific incident, the point you seem to be ignoring is that, due to climate change, events that would have been considered "black swans" historically will become more and more common, to the point that they are expected to occur.
I think that’s a misreading of the entire book. A black swan event is a rare, high-impact outlier that is nearly impossible to predict under normal circumstances, but is rationalized as having been inevitable in hindsight.
For whatever reason, you continue to try to ignore the point I'm making, which is that, in terms of natural disasters related to climate in particular, what would have been "rare, high-impact outlier[s]" are increasingly becoming common enough to be not rare and not outliers.
Anticipation is one thing, effective response in the seconds before disaster strikes is quite another thing. This might not have been an absolute black swan, but even with foresight it is challenging in the extreme to avoid risk.
I've been reviewing what coverage I can find of the present event in Nepal/China, in context with Section 5.1, "Comprehensive approach to disaster risk management", of TFA.
It seems that what would be required would be:
- Active surveillance of glacial lake formation.
- Active mitigation of glacial lakes, reducing risk.
- Warning and response infrastructure, procedures, and protocols along the likly flood path.
From video of what I presume are among the worst-hit areas (see: <https://twitterwebviewer.com/?tweet=2092542957060841592>), there appear to have been at best a few seconds of warning. Very robust structures are demolished virtually instantly. Even had people been sheltering within those structures, or headed up-slope above the water flow, either structural integrity would prove insufficient, or response time inadequate to reach a safe elevation above the debris flow. The latter problem is compounded by what appears to be an extraordinarily strong air blast (likely hurricane-strength or greater) as well as massive amounts of airborne debris, much of it rock.
Terrain is severely constrained in the region, and the only buildable regions are in river valleys themselves. The Gyirong Port border crossing is located deep within a river channel, and despite robust construction simply could not survive the event.
(Take a few minutes to examine the region around the port itself ... there are several communities and businesses all well within the disaster zone, and I suspect that obliteration to those matches or exceeds what was captured on video at the crossing itself.)
From the first video at this Twitter post, a camera situated roughly 20m above the base terrain did not survive the event (though it transmitted for roughly a minute).
A second camera (I believe near the same location) shows similarly catastrophic damage, and no chance for anyone at base level to climb to a safe elevation before being overtaken by the debris flow.
Climbing that far would require 4--8 minutes for even a highly-fit person. Available response time in the videos I've seen is on the order of 1--2 minutes. Anyone beginning within the debris zone is already walking dead.
As the Cowboy Junkies said:
But if there's on thing in my life
That these years have taught
It's that you can always see it coming
But you can never stop it
Anticipation isn't sufficient. Other than entirely abandoning such locations during all periods of high risk, loss of life is likely, and catastrophic property and infrastructure damage inevitable.
When I was researching this morning I found papers related to this kind of risk from at least 2000. Given 20 years there could have been things done I think. And there is a lot of settlement on the tops of the ranges in that area too.. Maybe the roads have to be on the river valley, but not everything else. People living there could have been offered alternative land to move out of the path of it.. monitoring and early warning could have been set up.. at the checkpoint, if it had to be there, there could have been a big evacuation tunnel carved into the hillside, or something.. I guess Nepal doesn't have a lot of resources though.
The same thing even happened a year ago in the sample place, but at a smaller size
https://www.stimson.org/2025/investigating-an-emerging-clima...
Perpendicular is not the scientifically best path. 45 degree angle is the best angle if the threat is moving toward you at the same velocity that you can move. As the velocity of the threat increases, the angle gets closer to perpendicular. The size of the threat and distance of course matter as well. I think about this before tree felling. In chainsaw classes they teach you to move at a 45.
There was another similar flood on the same river about a year or two ago. The problem was the the glacial flooding started in Tibet and affected people just over the border (one of the videos is from the border crossing). There's no international data sharing for this sort of thing between China and Nepal and Nepal can't deploy sensors in Tibet to give sufficient warning.
It is possible if you consider madaxe_again's theory(comment here). If the debris just started descending without interruption, there would be no receding.
The great flood myths across the world are quite possibly ancestral memories of this kind of flood on a continental scale. Retreating ice age glaciers would make lakes the size of states held at bay by an impromptu dam of various kinds of debris (or more glacier) which then would break dumping great lake amounts of water hundreds of miles into the ocean within days. This kind of thing probably happened in lots of places.
It is supposed that such an event happened, when the land between continental Europe and England got flooded. This was as well during a warmer period when glacier melted. And there was human population on that land.
I think the Japan tsunami videos showed as many, but it was spread out over the course of almost 2hrs and happened in slow motion over a large area. You could see some cars speeding to safety while others were washed away. Some stayed in taller structures assuming they were safe and were slowly washed away.
It is harrowing. It also explains why the villages in my ancestral region in India (JK, HP, UK) with close cultural and ethnic ties with Nepal used to build them at the upper portions of the sides of mountains/hills and only shifted to building at the bottom of those kinds of valleys when motorized roads became a thing in the 20th century.
Rescue operations in Nepal are in good hands, but this is sadly because those same response orgs had to respond to a similarly brutal cloud burst floods back in 2013 [0], 2021 [1] and 2025 [2].
It also shows the very real and brutal effect climate change is already having, and will only get worse.
it's a popular area for tourists and mountaineers, but also i think it's a lot easier to estimate missing/dead tourists since most of them will be there with tours/companies that have to keep track of exactly where they are.
Syabru Besi is downriver of the border and the starting point for the Langtang valley trek which is probably the third most popular trekking location in Nepal (behind Everest basecamp and Annapurna circuit). I think the tourist data they have is from tourists that are traveling with guides but from my experience many tourists also bypass the official requirements and trek solo so the number could be much higher if the Langtang is affected.
Reminded me of the Huascaran avalanche (1970, killed approx 30K people) [0]. I'm surprised this is not also in the thousands of casualties (perhaps it'll get there) [0]
>Much of the landform has been shaped by the actions of glaciers and the shrinkage of the bay over long periods of time
This would support your notion. Albeit ridiculous.
>Finally starting in the Late Ordovician and continuing into the Silurian did the gradual regional subsidence of this part of the Canadian Shield form the Hudson Bay Basin
This would not.
I cannot decide whether to laugh, or downvote your comment without more context. That I did some research and learning to decide to comment instead leaves me happy and satisfied that your comment was not completely worthless.
The debris flow that has just happened doesn’t appear to be a glacial outburst.
Rather, the entire front face of a glacier at high elevation sheared off, likely millions of tonnes of material at least, crashed down a steep runnel, slammed into the opposing slope on the other side of the valley at the bottom, made that partially collapse, dammed the river for several minutes, and then all descended at high speed as the dam failed, with the results we see.
Some reportage is still saying there was an earthquake - there wasn’t - the landslide itself was the source of the seismic waves.
Brilliant analysis! Although china is notoriously bad at reporting earthquake data, I assumed in this case they were open and honest. It made sense that an earthquake would trigger this event. I do not fault anyone for interpreting the data this way. The USGS has been the agency I most trust in the federal government.
USGS is a fact finding organization. They do not regulate. They have been around since 1879. The land surveys they have done made huge impact on society. The reliability of surveys that they have facilitated has made an impact on industrial civilization that few will understand or ever hear about.
exceptionaly brutal cctv footage from the tibet/nepal border, so many people that there is a tiny chance that perhaps one of them was tossed clear, but of the rest there will be no remains.
other videos shows that the flood "water" is so thick with mud that it is sheering off in sheets and one more shows it ripping out a concrete bridge that then floats away on top.
*disturbing video
In the future, don't go close to mountains during monsoon season - late May to August end; that period is specifically for Southeast Asia. For the rest of the world, you can find it out.
I read this wasn't due to rain but a glacial collapse. It sounds to me like the additional advice would be that due to a warming climate, avoid being under a glacier at all costs?
Down stream of a glacier, in the run off water shed.
As I've heard tell, this was a glacial collapse into and blocking a river, which then built up a head of pressure behind it, bursting to release a hammer blow of river water and debris that travelled a great distance.
Similar things can happen due to landslides into rivers; it depends on the topology of the land, here long narrow valleys carved out by heavy water flows.
The warning being, don't live in a natural "drainpipe".
In mountainous regions that's often not much of an option, there's a lot of vertical sides and valley bottoms.
The rivers in that area are pretty small. You would have to block them for days before there is a risk of a massive flash flood.
From what I've understood, the collapsing glacier either contained enough liquid water or melted enough from the impact that it continued flowing downstream. It covered ~20 horizontal kilometers in about 7 minutes before hitting the border crossing.
Sure, if every part of rugged terrain were monitored with sufficient frequency to detect such a change.
That might take some infrastructure to cover everywhere such things can happen (eg: the beds of rivers in Western Australia's Pilbara and Kimberley regions have a high flash flooding risk in the wet season.
>simulated worst-case outburst events from these lakes both in the Tibetan town of Nyalam and downstream at the border with Nepal
For context that's not where the flood happened, there's a massive mountain range in between those vallies reaching over 8000m (Shishapangma).
In earth science there are thousands of worst case scenario models published, but it's hard to actually predict reality.
Its easy though to bury sensors and sound sirens.
Near Juneau, Alaska, USA, the Mendenhall glacier has repeatedly, over the last few years, had a Glacial Lake Outburst Flood. Not nearly as catastrophic as the one in Nepal but it did flood areas near Mendenhall River in Juneau. The latest event was August 13, 2026.
https://www.weather.gov/ajk/suicidebasin
Context: https://www.cnn.com/2026/08/26/world/live-news/nepal-flash-f...
I don't think I've seen a snuff film of that scale before. I'm not good with even fictional horror. This may haunt my dreams. For most of the people there was just nothing they could do. But others would have had a chance if they had run perpendicular to the flow and climbed like their life depended on it. I'll try to remember that the next time I'm fleeing in panic from a flash flood.
Looks like a warning siren could have saved some lives. But apparently this was a black swan.
| But apparently this was a black swan.
What is your definition of black swan? This paper is from 2022 and scientists have been warning about climate change for decades. It's not like this possibility wasn't anticipated. It seems likely we'll see more glacial events as the atmosphere warms.
There have been maybe three such events in the 21st century (glacier or landslides producing more than a magnitude 5 quake), and none of them have happened in an area like the Himalayas. The other two were in Alaska on Mt Steller in 2005 and the Lamplugh Glacier in 2016, neither of which produced massive downstream floods.
It usually takes entire icebergs calving off to produce such seismic events and intense monsoons to create such flooding.
> There have been maybe three such events in the 21st century
It seems that past history (especially recent) will not be a good predictor of future events.
Spoiler alert: that’s the whole point of a black swan event.
A black swan event is an event that is unpredictable because it is so rare.
While I'd wait for confirmation about the cause of this specific incident, the point you seem to be ignoring is that, due to climate change, events that would have been considered "black swans" historically will become more and more common, to the point that they are expected to occur.
I think that’s a misreading of the entire book. A black swan event is a rare, high-impact outlier that is nearly impossible to predict under normal circumstances, but is rationalized as having been inevitable in hindsight.
For whatever reason, you continue to try to ignore the point I'm making, which is that, in terms of natural disasters related to climate in particular, what would have been "rare, high-impact outlier[s]" are increasingly becoming common enough to be not rare and not outliers.
And you continue to ignore what I said (and what the book said). The whole point of a black swan event is exactly what you just described.
It’s the inflection point when our priors change.
Anticipation is one thing, effective response in the seconds before disaster strikes is quite another thing. This might not have been an absolute black swan, but even with foresight it is challenging in the extreme to avoid risk.
I've been reviewing what coverage I can find of the present event in Nepal/China, in context with Section 5.1, "Comprehensive approach to disaster risk management", of TFA.
It seems that what would be required would be:
- Active surveillance of glacial lake formation.
- Active mitigation of glacial lakes, reducing risk.
- Warning and response infrastructure, procedures, and protocols along the likly flood path.
From video of what I presume are among the worst-hit areas (see: <https://twitterwebviewer.com/?tweet=2092542957060841592>), there appear to have been at best a few seconds of warning. Very robust structures are demolished virtually instantly. Even had people been sheltering within those structures, or headed up-slope above the water flow, either structural integrity would prove insufficient, or response time inadequate to reach a safe elevation above the debris flow. The latter problem is compounded by what appears to be an extraordinarily strong air blast (likely hurricane-strength or greater) as well as massive amounts of airborne debris, much of it rock.
Terrain is severely constrained in the region, and the only buildable regions are in river valleys themselves. The Gyirong Port border crossing is located deep within a river channel, and despite robust construction simply could not survive the event.
See:
<https://en.wikipedia.org/wiki/Gyirong_Port> (Wikipedia article on the port.)
Map / satellite view: <https://www.google.com/maps/@28.2792579,85.3752907,1341m/dat...>
(Take a few minutes to examine the region around the port itself ... there are several communities and businesses all well within the disaster zone, and I suspect that obliteration to those matches or exceeds what was captured on video at the crossing itself.)
From the first video at this Twitter post, a camera situated roughly 20m above the base terrain did not survive the event (though it transmitted for roughly a minute).
A second camera (I believe near the same location) shows similarly catastrophic damage, and no chance for anyone at base level to climb to a safe elevation before being overtaken by the debris flow.
Wikipedia notes "Floodwaters reached settlements as high as 270 feet (80 m) above the river level", citing <https://english.onlinekhabar.com/rasuwa-flood-in-pictures.ht...>.
Climbing that far would require 4--8 minutes for even a highly-fit person. Available response time in the videos I've seen is on the order of 1--2 minutes. Anyone beginning within the debris zone is already walking dead.
As the Cowboy Junkies said:
Anticipation isn't sufficient. Other than entirely abandoning such locations during all periods of high risk, loss of life is likely, and catastrophic property and infrastructure damage inevitable.<https://twitterwebviewer.com/?tweet=2092542957060841592>
When I was researching this morning I found papers related to this kind of risk from at least 2000. Given 20 years there could have been things done I think. And there is a lot of settlement on the tops of the ranges in that area too.. Maybe the roads have to be on the river valley, but not everything else. People living there could have been offered alternative land to move out of the path of it.. monitoring and early warning could have been set up.. at the checkpoint, if it had to be there, there could have been a big evacuation tunnel carved into the hillside, or something.. I guess Nepal doesn't have a lot of resources though. The same thing even happened a year ago in the sample place, but at a smaller size https://www.stimson.org/2025/investigating-an-emerging-clima...
Perpendicular is not the scientifically best path. 45 degree angle is the best angle if the threat is moving toward you at the same velocity that you can move. As the velocity of the threat increases, the angle gets closer to perpendicular. The size of the threat and distance of course matter as well. I think about this before tree felling. In chainsaw classes they teach you to move at a 45.
Looking at the footage, the water/avalanche was moving far faster than anyone could move on foot. Well over 100 km/h, I would estimate.
Likewise if your car stalls on a railroad crossing, run at a 45 degree angle toward the train. This puts you away from the path of flying debris.
There was another similar flood on the same river about a year or two ago. The problem was the the glacial flooding started in Tibet and affected people just over the border (one of the videos is from the border crossing). There's no international data sharing for this sort of thing between China and Nepal and Nepal can't deploy sensors in Tibet to give sufficient warning.
I wonder if the river went dry first, like the water receding off into the horizon before a tsunami?
It is possible if you consider madaxe_again's theory(comment here). If the debris just started descending without interruption, there would be no receding.
Well supposedly it was caused by a landslide blocking the river for a few minutes, then the dam burst all at once.
The great flood myths across the world are quite possibly ancestral memories of this kind of flood on a continental scale. Retreating ice age glaciers would make lakes the size of states held at bay by an impromptu dam of various kinds of debris (or more glacier) which then would break dumping great lake amounts of water hundreds of miles into the ocean within days. This kind of thing probably happened in lots of places.
It is supposed that such an event happened, when the land between continental Europe and England got flooded. This was as well during a warmer period when glacier melted. And there was human population on that land.
https://en.wikipedia.org/wiki/Doggerland
You just pushed me into a rabbit hole called the Zanclean megaflood.
https://en.wikipedia.org/wiki/Zanclean_flood
I think the Japan tsunami videos showed as many, but it was spread out over the course of almost 2hrs and happened in slow motion over a large area. You could see some cars speeding to safety while others were washed away. Some stayed in taller structures assuming they were safe and were slowly washed away.
It is harrowing. It also explains why the villages in my ancestral region in India (JK, HP, UK) with close cultural and ethnic ties with Nepal used to build them at the upper portions of the sides of mountains/hills and only shifted to building at the bottom of those kinds of valleys when motorized roads became a thing in the 20th century.
Rescue operations in Nepal are in good hands, but this is sadly because those same response orgs had to respond to a similarly brutal cloud burst floods back in 2013 [0], 2021 [1] and 2025 [2].
It also shows the very real and brutal effect climate change is already having, and will only get worse.
[0] - https://en.wikipedia.org/wiki/2013_North_India_floods
[1] - https://en.wikipedia.org/wiki/2021_Uttarakhand_flood
[2] - https://en.wikipedia.org/wiki/2025_Kishtwar_district_flash_f...
That makes sense. You can see lots of settlements on the hills above the sight of this flood too. I also found this study of the risk perceptions of people living there interesting too. https://www.sciencedirect.com/science/article/pii/S221242092...
150 confirmed with 47 Americans? Surprising fraction. Mountaineers or that area is popular for some reason?
it's a popular area for tourists and mountaineers, but also i think it's a lot easier to estimate missing/dead tourists since most of them will be there with tours/companies that have to keep track of exactly where they are.
Syabru Besi is downriver of the border and the starting point for the Langtang valley trek which is probably the third most popular trekking location in Nepal (behind Everest basecamp and Annapurna circuit). I think the tourist data they have is from tourists that are traveling with guides but from my experience many tourists also bypass the official requirements and trek solo so the number could be much higher if the Langtang is affected.
Likely the tourists are better accounted for than the locals. Numbers are likely much higher :(
i understand it as 150 dead, with more people missing, of which 47 are americans.
I feel like I've easily seen more than that get swept away in videos.
Way too early to get an accurate count
Nepal is popular for Westerners I think. Maybe for religious reasons?
Mountaineering.
For indians, you also have the religious aspect because the immigration center you go to to visit Mt Kailash is there.
That immigration building was the white one that got completely shredded in the popular video going around.
I have watched a few and they look like the four horsemen TBH.
Reminded me of this documentary I saw last year - https://www.arte.tv/en/videos/122807-000-A/arte-reportage/ . I thought it was the same lake
Reminded me of the Huascaran avalanche (1970, killed approx 30K people) [0]. I'm surprised this is not also in the thousands of casualties (perhaps it'll get there) [0]
https://en.wikipedia.org/wiki/1970_Huascar%C3%A1n_debris_ava...
It almost certainly is. Just too early right now.
I believe this is how the Hudson Bay was formed, in what must have been quite a sight.
Hyperbole?
>Much of the landform has been shaped by the actions of glaciers and the shrinkage of the bay over long periods of time
This would support your notion. Albeit ridiculous.
>Finally starting in the Late Ordovician and continuing into the Silurian did the gradual regional subsidence of this part of the Canadian Shield form the Hudson Bay Basin
This would not.
I cannot decide whether to laugh, or downvote your comment without more context. That I did some research and learning to decide to comment instead leaves me happy and satisfied that your comment was not completely worthless.
ref: https://en.wikipedia.org/wiki/Hudson_Bay
The debris flow that has just happened doesn’t appear to be a glacial outburst.
Rather, the entire front face of a glacier at high elevation sheared off, likely millions of tonnes of material at least, crashed down a steep runnel, slammed into the opposing slope on the other side of the valley at the bottom, made that partially collapse, dammed the river for several minutes, and then all descended at high speed as the dam failed, with the results we see.
Some reportage is still saying there was an earthquake - there wasn’t - the landslide itself was the source of the seismic waves.
https://earthquake.usgs.gov/earthquakes/eventpage/us7000tbwb...
Brilliant analysis! Although china is notoriously bad at reporting earthquake data, I assumed in this case they were open and honest. It made sense that an earthquake would trigger this event. I do not fault anyone for interpreting the data this way. The USGS has been the agency I most trust in the federal government.
USGS is a fact finding organization. They do not regulate. They have been around since 1879. The land surveys they have done made huge impact on society. The reliability of surveys that they have facilitated has made an impact on industrial civilization that few will understand or ever hear about.
GLOF, glacial lake outburst flood.
exceptionaly brutal cctv footage from the tibet/nepal border, so many people that there is a tiny chance that perhaps one of them was tossed clear, but of the rest there will be no remains. other videos shows that the flood "water" is so thick with mud that it is sheering off in sheets and one more shows it ripping out a concrete bridge that then floats away on top. *disturbing video
https://m.youtube.com/watch?v=rIVNeDuCF_k
Wrong link
https://m.youtube.com/watch?v=rIVNeDuCF_k
fixed, but some things are better off wrong perhaps
In the future, don't go close to mountains during monsoon season - late May to August end; that period is specifically for Southeast Asia. For the rest of the world, you can find it out.
This was a glacier collapse. https://www.zhihu.com/question/2075969425702741132/answer/20...
I read this wasn't due to rain but a glacial collapse. It sounds to me like the additional advice would be that due to a warming climate, avoid being under a glacier at all costs?
Down stream of a glacier, in the run off water shed.
As I've heard tell, this was a glacial collapse into and blocking a river, which then built up a head of pressure behind it, bursting to release a hammer blow of river water and debris that travelled a great distance.
Similar things can happen due to landslides into rivers; it depends on the topology of the land, here long narrow valleys carved out by heavy water flows.
The warning being, don't live in a natural "drainpipe".
In mountainous regions that's often not much of an option, there's a lot of vertical sides and valley bottoms.
The rivers in that area are pretty small. You would have to block them for days before there is a risk of a massive flash flood.
From what I've understood, the collapsing glacier either contained enough liquid water or melted enough from the impact that it continued flowing downstream. It covered ~20 horizontal kilometers in about 7 minutes before hitting the border crossing.
It sounds like there may have been some opportunity for warning then? If the thing was more of a "build up" ?
Sure, if every part of rugged terrain were monitored with sufficient frequency to detect such a change.
That might take some infrastructure to cover everywhere such things can happen (eg: the beds of rivers in Western Australia's Pilbara and Kimberley regions have a high flash flooding risk in the wet season.