I'm pretty sure we're all desensitized to this stuff, certainly I am. But this one, especially the first couple clips, got me. This was the first populated place hit by the flood, I'm sure they had zero warning. And if you look at google earth, there are only vertical cliffs/bluffs/mountainside all around. No way to get to higher ground. I imagine everyone in those first clips are dead.
https://www.youtube.com/shorts/r1cBJy-nCZo
You really need to see this place on a map with terrain (like google earth) to understand how [expletive] everyone was. Here's the coordinates for anyone interested.
28°16'43.97"N
85°22'40.00"E
At first, I was like, how. But it doesn't take much to figure out what a dire situation this was.
For reference, the Mississippi River has a flow rate somewhere around 600K cubic feet per second near New Orleans. The mississippi river is no way similar to the river/stream where this happened. The MS has an almost non existent slope at that point (roughly 0.00001 ft of fall per ft of run) and it's like half a mile wide and gets up to 100-200 feet deep. Conversely, this stream is about 100' wide, has almost no depth, and has a slope of more than 0.05 ft of fall per foot of run. Water is going to be more destructive here is the main takeaway.
Doing some back of napkin calcs with a ton of assumptions, the flow to get to ~35' deep in the area in the first part of the video about 50K cfs (should be noted, it could take only 60% of that flow depending on what n value is assigned as the roughness coefficient...like I said, lots of assumptions). Take 50K and assume the flows lasted 10 minutes (estimates vary wildly from a couple minutes to half an hour). I'd assume the peak of the flow happened within a couple minutes. But, we're just trying to get total volume (which is what I couldn't wrap my head around) and because I'm estimating flow using the peak height, I think we're okay trimming the tail off here.
50K cfs * 600 s = 30 million cubic feet of water
Where in the world did that much water come from?
Well, the cubed root of 30M is 310. So a cube of water 310x310x310' would get you that. But this is coming from a mountaintop, so cubes don't really exist, half of the slide is going to go the opposite direction, and I find it hard to believe you'll just spontaneously get a cut of 300'+ off the top of a mountain, so is it still possible? Just making stuff up, completely, trying to get to the 30M number at this point. Assume it's a 100' cut that comes 100' out. That's 5K sf of glacier along the ridge. That would take 6K linear feet of a failure to get to that 30M volume.
In the basin flowing directly to the stream, there is approximately 11K LF of ridge line. This is what it looks like, from a pic on google earth.
https://lh3.googleusercontent.com/grass ... 3skE=h1440
Here's the location of the 'earthquake' the USGS regsitered and then later came back to say it was actually a glacial slide. 28.271°N 85.515°E
https://earthquake.usgs.gov/earthquakes ... /executive
FWIW, all those calcs are assuming just water. All the downstream soil and debris and remaining snow/ice also counts until the debris settles out which is going to take some ground much flatter than 5%.This event was initially reported as a magnitude 4.4 earthquake. Additional analysis of long period seismic waves indicate that the seismic energy was instead generated by a glacial collapse and debris flow. The location of this event was estimated from satellite images.
All that to say, yeah, it's pretty easy to see how this happened. The sheer force of nature is both awe inspiring and terrifying.
