Worst-case glacial lake flood scenarios in a transboundary Himalayan basin 2022
nhess.copernicus.org81 points by totetsu 4 hours ago
81 points by totetsu 4 hours ago
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.
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.
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.
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.
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.
Likely the tourists are better accounted for than the locals. Numbers are likely much higher :(
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.
i understand it as 150 dead, with more people missing, of which 47 are americans.
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...
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.
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
Wrong link
https://m.youtube.com/watch?v=rIVNeDuCF_k
fixed, but some things are better off wrong perhaps