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The mechanics of the Nepali flash flood

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Re: The mechanics of the Nepali flash flood

#21

Post by Fricken »

debo_ wrote: post #12
glimshe wrote: post #6

I haven't yet been able to properly internalize the horror of this scene. Maybe because we're exposed to so many images from disaster and action movies/videogames, I got somewhat desensitized to the "graphics", so to speak. It's like my brain is denial. At the same time, I know this is real and a tragedy in an unimaginable scale. Every "little walking figure" is a full human being with dreams, fears and a rich life s…

About 18 years ago, some guy at work was laughing at a video of someone being blown to pieces by an explosive device. People kept walking by his desk and laughing, I suppose because it looked so cartoonish that it felt more like looney tunes than real life. As an experiment, I showed the same video to my 85-year old grandmother, and she cried out in horror and prayed for the people in the video for a solid hour after…

I go around with the general awareness that about 200k people die every day. I know that disasters and tragedies happen around the world on a regular basis. I know that cameras are nearly ubiquitous even in the developing world, so there is a good chance that any sensational event will be recorded and posted on the internet. Armed with these priors it's not a huge surprise or shock to me. It is still impressive, however.

Re: The mechanics of the Nepali flash flood

#22

Post by IG_Semmelweiss »

kulahan wrote: post #7
pm2222 wrote: post #2

https://apnews.com/article/climate-change-nepal-tibet-glacie... CCTV footage is there. Horrific scene. When you see it coming at you it’s already too late.

It's awful to see dozens of people running and knowing they're all gone. It wasn't even close. They were so small compared to that absolute FORCE .

Is it correct to say that the video looks far worse than it actually is ?

As in, the dust/mud particles sprayed & floating in the air do not have the force to do harm beyond vision or breathing impairment, similar to the dust from a collapsing building, or the lead shockwave of a nuclear bomb detonation.

Of course, it looks terrible, and certainly somethingbut its not a reason to perish as long as you can stay away from the following water wall and mud current that does strike sometime after.

Re: The mechanics of the Nepali flash flood

#24

Post by margalabargala »

IG_Semmelweiss wrote: post #22
kulahan wrote: post #7

Earlier quoted context omitted.

It's awful to see dozens of people running and knowing they're all gone. It wasn't even close. They were so small compared to that absolute FORCE .

Is it correct to say that the video looks far worse than it actually is ? As in, the dust/mud particles sprayed & floating in the air do not have the force to do harm beyond vision or breathing impairment, similar to the dust from a collapsing building, or the lead shockwave of a nuclear bomb detonation. Of course, it looks terrible, and certainly somethingbut its not a reason to perish as long as you can stay away f…

No, that's not correct.

The length of time between the spray you mention, and the impact of the water wall, is single digit seconds. It doesn't make a difference.

Re: The mechanics of the Nepali flash flood

#25

Post by UncleOxidant »

kulahan wrote: post #11
1attice wrote: post #10

Earlier quoted context omitted.

This is true, and, relatedly, is the feeling I have about all of climate change. By the numbers, it won't be close. Of course, this little preview is itself anthropogenic. This horrific disaster is the thinnest tendril of the monster we have unleashed.

Both figuratively and literally, this experience was the tip of the iceberg. Terrifying. People might think I'm crazy, but I'm choosing my retirement location 100% based on resistance to climate change. Local water, too much humidity for massive fires, too cold for insane heatwaves... you get it.

I've seen recommendations for locations near the Great Lakes. Upper peninsula of MI, for example. Plenty of water. A warming climate should actually make the winters there somewhat less harsh.

Re: The mechanics of the Nepali flash flood

#26

Post by abrowne »

UncleOxidant wrote: post #25
kulahan wrote: post #11

Earlier quoted context omitted.

Both figuratively and literally, this experience was the tip of the iceberg. Terrifying. People might think I'm crazy, but I'm choosing my retirement location 100% based on resistance to climate change. Local water, too much humidity for massive fires, too cold for insane heatwaves... you get it.

I've seen recommendations for locations near the Great Lakes. Upper peninsula of MI, for example. Plenty of water. A warming climate should actually make the winters there somewhat less harsh.

Wildfire smoke will be the big question there. It's started to be bad for a week or two a year in Minneapolis, and is only worse the closer you are to the boreal forest.

Re: The mechanics of the Nepali flash flood

#27

Post by FireBeyond »

sandeepkd wrote: post #17
1attice wrote: post #10

Earlier quoted context omitted.

This is true, and, relatedly, is the feeling I have about all of climate change. By the numbers, it won't be close. Of course, this little preview is itself anthropogenic. This horrific disaster is the thinnest tendril of the monster we have unleashed.

I do not know if I would consider stopping the climate change as a solution for all such events. Watching the video makes you realize how small you are in front of the nature. It feels painful to even watch it but its an eyeopener at the same time. Its a misconception to think that the climate would always remain same, nature is an constantly moving/changing entity. What might be perceived as destruction is also the…

Mt St Helens erupted in 1980. The landslide alone was 3.3 billion cubic yards, that traveled 15mi at speeds of up to 155mph, and buried 23 square miles to an average depth of 150ft, and up to 600ft, within 10 minutes.

The blast flattened 230 sq mi of forest in minutes.

540 million tons of ash fell in 9 hours, affecting 22,000 sq mi.

The mudflow (lahar) was this debris mixing with 170 million cubic yards of glacial ice and snow, moving at 80 mph.

People liked to make smart ass comments about people who took photos "and would soon be dead" - "they were miles away, they could have left". For a lot of them? No.

The sheer magnitude of these events is truly unimaginable, even if you "were there" (nearby).

And MSH was barely a 5 on the VEI 0-8 (roughly) logarithmic scale, though you can't map to death toll easily.

Pinatubo in 1991 was a high 6. Krakatoa too. Tambora is the largest we know, in 1815, VEI 7, and is estimated at eighty times more output than MSH, and triggered the "Year Without a Summer" globally (https://en.wikipedia.org/wiki/Year_Without_a_Summer) that pulled down average -global- temperatures by a full degree over the course of a year. It completely disrupted the monsoon season throughout Asia, leading to flash flooding events like this becoming a very regular occurrence.

I think some of these types of stats are the closest terrestrial things we have at the limits of human comprehensibility (probably only eclipsed by "interstellar distances").

Re: The mechanics of the Nepali flash flood

#28

Post by SoftTalker »

abrowne wrote: post #26
UncleOxidant wrote: post #25

Earlier quoted context omitted.

I've seen recommendations for locations near the Great Lakes. Upper peninsula of MI, for example. Plenty of water. A warming climate should actually make the winters there somewhat less harsh.

Wildfire smoke will be the big question there. It's started to be bad for a week or two a year in Minneapolis, and is only worse the closer you are to the boreal forest.

Wildfires only a problem until the overgrowth is burned off. When there's not enough to sustain a large spreading fire, they will stop happening.

Re: The mechanics of the Nepali flash flood

#29

Post by testing22321 »

abrowne wrote: post #26
UncleOxidant wrote: post #25

Earlier quoted context omitted.

I've seen recommendations for locations near the Great Lakes. Upper peninsula of MI, for example. Plenty of water. A warming climate should actually make the winters there somewhat less harsh.

Wildfire smoke will be the big question there. It's started to be bad for a week or two a year in Minneapolis, and is only worse the closer you are to the boreal forest.

And the failure of basic services like water and power.

Given it took FEMA ten days to get power restored to the super dome, how long will responses be when there are many simultaneous disasters of that size or bigger? With the current admin the answer could be “indefinite”

Re: The mechanics of the Nepali flash flood

#30

Post by AlotOfReading »

tintor wrote: post #13

Is Switzerland exposed to similar risk, given the amount of glaciers?

Probably not. Most alpine valleys were carved by glaciers and have a characteristic U-shaped profile. When you get a landslide into a glacial valley, it hits the relatively flat floor and breaks itself apart. The valleys themselves are usually wide enough that they don't dam either. The alps also have significantly less relief than the Himalayas.

The valley where the floods occurred in Nepal has a V-shape, and the peaks around it have much more relief. It's much easier for a large landslide to fill the bottom, creating a dam that can burst, or just continue down the valley without wasting all its energy on a broad flat plain at the bottom. The upper valley immediately below the cliff face that toppled was also a glacial U-shaped valley though, so this speculation might need adjustment as more work is done.

It's worth emphasizing just how much less monitored and dangerous Nepal's mountains are though. The (greater) Himalayas are unlike any other mountain ranges I've ever seen.

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