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.

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:

  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

<https://twitterwebviewer.com/?tweet=2092542957060841592>

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.

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.

You just pushed me into a rabbit hole called the Zanclean megaflood.

https://en.wikipedia.org/wiki/Zanclean_flood

The Missoula Floods in the northwestern US were a similar sort of event, though I'm not sure how the scale compares.

https://en.wikipedia.org/wiki/Missoula_floods

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

This.

You could probably count 100+ people in the death zone of the border crossing video alone. The final death toll will be terrible, with most never found.

Zero chance the actual death count is sub-1000

I feel like I've easily seen more than that get swept away in videos.

Way too early to get an accurate count

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.

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" ?