Was this the hardest it can possibly rain? (MASSIVE destruction to mountain communities)

本站添加: 2026-05-12

[00:00:00]What's happening folks? Geologist Philip Prince looking out over the site of one of the craziest weather disasters the United States has ever seen. It actually did happen the day after Woodstock ended in 1969. And this event is the remnants of Hurricane Camille getting into the Blue Ridge Mountains of Virginia. Uh, interestingly, this weather event which brought as much as 30 inches of rainfall in just a few hours did not affect uh the really big high mountains uh you see here in the background of this map uh anywhere near to the extent that it affected some of these smaller but very rough mountains that you see uh in the foreground of the map here. This is in uh Nelson and a little bit of Albam Marl County, Virginia. Uh got a town called Lovingston, Virginia that sits right here. That's a pretty good frame of reference. When this event happened, uh people had gone to bed. Incredible rainfall began. Uh and overnight in the dark, you had thousands of landslides.

[00:01:06]They were debris flow style landslides were sort of liquefied soil, rocks, trees, whatever comes down the mountain side. People said you could feel it sort of trembling and and shaking almost like the almost like the earth was moving. Uh folks said that if you if you went outside in the rain, it was raining so hard that you almost couldn't breathe. Like you would want to try to cover cover your mouth to to keep some of the rain from actually going in when you took a breath. Reports of birds and small animals drowning. An absolutely extreme event in every sense of the word. beyond the area that's that's circled here. Incredible flooding uh that extended well down the the James River system as well. But that's really what you would expect when you put what would be probably half half of the year's worth of rainfall or maybe even a bit more than that onto rugged land literally in in just a few hours just in an overnight period of time. Where are we here? Uh, and what does that have to do with the weather system that actually caused this disaster? I'm going to zoom it out here. Got to take a look at a bigger chunk of the eastern United States. See what was going on. Uh, Hurricane Camille was an incredible storm when it came ashore off the Gulf of Mexico. Um, after it moved up and into sort of the interior of the US, as is typical of those systems, things were were obviously sort of slowing down for it. And by the time it was getting over into the Appalachin Mountains, uh really it was was sort of a of a low pressure circulation here. Got that counterclockwise movement and really didn't have extreme rainfall. Didn't have wind associated with it very much at all. Sort of a sort of a storm on the way out. this particular summer 1969 uh did have notable characteristic of first of all just a lot of rain within the region. So there was a lot of water in the soil and available in the lower levels of the atmosphere. And at this particular time down in northern North Carolina had an incredibly moist sort of soupy air mass that could be drawn by that circulation. I move it like that. uh could be drawn up sort of into this mountainous area uh in the in the Virginia Blue Ridge. Right. So, we'll uh get that labeled up here. We'll just give it a give it the moisture label there. So when that moist air was drawn by the circulation of of sort of a dying storm really at this point uh into that mountainous terrain and also uh into interaction with sort of another weather boundary there. Uh it it sort of brought the storm back to life at least in the rainfall sense of the word. So with that in incredible amount of water vapor available uh mixing with with these various weather details allow that moist air to rise, expand, cool, and produce huge, incredible, unbelievable amounts of rainfall. And there's really nothing in the way between where the word moisture is written there uh and the mountains that it fell on. So all of that all of that rainfall potential went straight essentially to the first rough topography that it could find which happened to be the smaller almost foothills in a sense. I mean they're very much rough mountains but they're they're a little bit out away from the highest peaks of the Blue Ridge in this particular area. You zoom in close on these mountains. They're really rough rugged irregular mountain sides.

[00:05:03]kind of highlight them out here. They have a tremendous amount of texture and all those little ravines with very steep upper parts had the potential of producing these these fluidized landslides and just about all of them did to absolutely disastrous effect.

[00:05:20]Now, what what do you see here today?

[00:05:23]Um, in the Appalachins, forests tend to recover remarkably quickly from events like this. uh at least in terms of growing trees back on the landscape. But if you have the right tools to see the landscape, you can absolutely still see the scars from storm event like this.

[00:05:41]So, we're going to take that map away, bring in some LAR imagery here. This LAR is 1 meter resolution. It allows you to see the land surface in incredible detail. And right in front of us there, see several scars left behind by these landslides that happened during the night of August 19th into into August 20th, 1969.

[00:06:11]Some of these almost ripped like all of the soil out of these little concave sort of B-shaped areas of the mountain side. One thing that's notable that we'll mention again, uh you don't don't see any damage from the storm in areas like this, right? So the the ridgetops and certainly the mountain tops are never affected. And these landslides actually kept happening after the rain had stopped. And that's very good evidence that they are in fact landslide events related to the soil basically losing its strength due to being oversaturated starting to slide and then because everything downhill is saturated as that soil runs over it all turns to liquid and you have sort of a runaway almost snowball type of effect. When folks see events like this, sometimes they wonder if really hard rainfall was essentially like like gouging out the mountain side or something like that. And if you look at those scars, you could actually sort of develop in your mind a theory that something like that was happening. But we know that's not the case. Uh again, for the two reasons just listed, you'll never see this problem on the ridgetop or on any of these convex parts of the mountain side. And you still see these happening after the rain stops, which also makes the situation dangerous because when the rain stops, you think you can go outside and start looking around and then you might have another one of these mobile landslides come down on top of you. Literally thousands of these within a very limited area. And as you look around on the map here, you can sort of tune your eye to what those scars look like. Just about every concave part of the mountain side has one in it. And that extent of landsliding here um was certainly one of, if not the most extreme expression of this really that that Virginia or even the Appalachins has seen in in recorded history. What do these features represent geologically? How do they work? How can you sort of read the mountain side and get a sense of where they uh where they might happen? Going to sketch that out in paint here. Uh, and then we're going to come back, look at some more maps, and actually look at some photo evidence of what this event looked like uh, after it happened. The Virginia Geological Survey has done a very good job of recording, documenting this event, and some of the records that they have online that you can go and check out are are really worth a look.

[00:08:45]So, we'll get started up and paint here.

[00:08:46]Hang on just a minute. Okay. So what are you actually seeing when you sort of look at those scars there uh that are so visible in the LAR imagery? So we'll set ourselves up um sort of a basic hollow and and stream drainage on a mountain side. That term hollow use it a lot on this channel because talk about landscapes a lot and I always have to stipulate here in Appalachia we got a we got a hollow and we got a holler. um whole thing that we're drawing here is is the holler because it's kind of a ravine, stream valley, whatever you hear a term cove sometimes accomplishing the same the same meaning. But a hollow is a concave sort of a you know slightly B-shaped feature on the side of a mountain. Actually spray painting in a couple of them here. these slightly darker areas where they're a little bit kind of dished out, a little bit less light getting in there. Um, just trying to use the uh the shading here to to give you a sense that that's a slightly differently shaped part of the hillside.

[00:09:55]And those hollows are are a big part of uh the story here. Now, down the very lowest part of our sketch here, you would have uh a little stream channel because you're looking at a landform that's sort of collecting water and routing it down into uh into that flowing channel. So, we'll we'll mark that little stream in in blue, but you get up here uh to the top of it and and the stream channel ends, right? If you're walking up that stream, you'd suddenly come out into the into the forest there. you're really high up on the mountain is basically dry up there.

[00:10:31]U when you have one of these extreme rainfall events and in the Appalachins something as low as about 5 in in 24 hours is actually enough to do this particularly if it's if it's extremely sudden and intense.

[00:10:45]you end up saturating the soil up here in the hollow up above the top of the stream right there and that causes a landslide that because the soil's saturated as it goes downhill it sort of turns into liquid uh and then it's off to the races basically following the following the stream channel down the mountain and in the case uh of this area in Virginia that was affected by the remnants of Camille we've been looking at Nelson counties so far and Nelson and Albamaral counties were the were the ones that absolutely got the worst of this. Uh pretty much any of those particularly shaded areas that I've illustrated here would have had one of these landslides uh up in the hollow and it would have liquefied and gone downhill and joined other ones and basically you end up sort of gutting gutting all of these hollows of their soil. Uh saturated soil of this type would weigh per per cubic yard. So imagine a cube of it, three feet on each side. Um over over 3,000 pounds with the amount of solid rock debris that you would have in it. Um 3500 4,000. Who knows? Uh but you're looking at over over a ton of material per cubic yard.

[00:12:05]And these are really really big scars, right? So, uh, the the amount of tonnage of wet soil that went down the mountain at once is is almost hard to believe.

[00:12:15]And of course, for folks that were downhill of that, it it turned into certainly the greatest disaster within within this county and probably within within this region within recorded history. Um, so when you look at that image, you're essentially seeing the scarring like we have it now. Um whereas before it happened, you would have had these nice sort of smooth slopes. And in this area that we're looking at, if if it is, you know, one of these hollow type features where it's a little bit concave and it's steep enough, it's going to have one of these crazy scars in it. And the scar is going to have sort of that steep lip um on the side of it there where the material all slid away and went down towards the stream channel. So we're slowly but surely kind of making our way towards the appearance that you have uh with the LAR there. And of course we want to take another look at that momentarily and hopefully it will uh it will make more sense after you see this. So if you had seen this immediately after the storm had happened, um all of these scars would have been bare bare earth essentially. Most of them actually scoured down to the bedrock, but they would have have still had that soil color. So it would look like the mountain was sort of bleeding bleeding mud almost, but uh it's not just mud, boulders, trees, everything else, right?

[00:13:40]So So that's the overall look there.

[00:13:43]And in terms of a crosssection here, see if we can get this going without running out of room. We'll we'll let that one run off the edge. No problem there, because I think we can do what we need to do on the side here.

[00:14:01]So, the the problematic material here is is what we just filled in. It's um it's just that little covering of soil.

[00:14:08]Apparently, I have a line that's not closed there. find that hard to believe.

[00:14:13]Was that the problem?

[00:14:16]Sure enough. Okay. So, what I just marked there in gray, that's the bedrock, which in this case has all these crazy fold structures in it. Um, but in terms of this event and what it did to the land, the the bedrock there really is not it it's really not involved in it. Um this is this is entirely something that's going on within the topography uh on on the land surface. Uh and it's involving just that thin layer of of gray uh soil that we call. That means it's it's sort of rock fragments that tumble down uh and pile up. And we'll actually add kind of some of these little little rock outcrops almost like cliffs here where that gray rock is actually at the surface. And over time, that's what's supplying that uh that brown layer of soil there. So, when you have one of these extreme storms, in this particular case, you're looking at at 5 in or more of rainfall an hour for several hours.

[00:15:21]Saturate that soil up top. it starts sliding and it's just going to clean out every other bit of soil in its way as it travels down the uh as it travels down the mountain. So, what you end up with is something like we got there. So, this is basically the cutaway view of what we got drawn at the uh what we got drawn at the left there. And down underneath that um you actually would be seeing you would be seeing that bedrock. We'll actually kind of color that in a little bit.

[00:15:53]So you you'd see the bedrock underneath the soil that has been scoured away, but the bedrock really is not changed. Um you you're just uh you're just removing its covering of material. And in that sense, uh this isn't really changing the the mountain in terms of its overall shape and its deeper structure. Um it it's almost like a house cleaning type of effect. Um, probably this house cleaning is because when you're dealing with something at the scale of a mountain, that is absolutely as destructive as you can get. These things move fast and because they follow waterways that people tend to live along. You might live on a tiny little creek that would never flood your house, but if you put a bunch of these big debris flows in it, um it's going to essentially bulldoze your your house and they will be going 20 miles an hour or something like that in the dark absolute worst case scenario.

[00:16:50]So, in terms of the bigger picture, uh actually get a new uh say goodbye. I hate to do it.

[00:17:03]Kind of look towards any given mountain side here in the in the southern Appalachins. You can uh do a pretty good job of um you know, kind of like organizing this thing out into these hollow shapes and more of what we would call spur type ridges. Uh and and really all you're doing is setting up areas here that that are basically convex and that that shed material uh down into some of the concave areas.

[00:17:41]Okay. So there's sort of your default your default Appalachin mountain side.

[00:17:45]And that goes for for just about anywhere on Earth where where water erosion uh is is going to be the dominant process for sure. uh glacially sculpted mountains can end up having somewhat different patterns, but in this particular case, this actually does a pretty good job of uh showing us what we need to see here. So, you've got got your drainages coming down out from between those more convex spur ridges there. And when you get an event like this going on way up here in the hollows, got your landslides starting and as they make their way down, they progress and sort of develop into these huge debris flow type of events. Just got our little lines here to try to to give a sense of that sort of almost like corrugated effect there. Um, and man, when you got every single thing going here at once, just the sheer amount of material that's going to come out of these drainages, uh, in some cases just in a few minutes is is absolutely staggering. And this is what you would have seen after, uh, after Camille in Virginia. Just basically everywhere that could possibly source a landslide due to steepness uh, and have that kind of run away into a debris flow did it. even these little little tiny areas down here that aren't even the full the full height of the mountain.

[00:19:11]Right? So, let's go back to the maps, take a look at this sort of in in real life and actually look at even some photos from the event which are really important for understanding what I have just drawn here would actually look like in real life. So, hang on just a minute.

[00:19:27]Okay. So what we sketched out there is is in effect the geologic significance and origin of the scars that you're you're looking at here on this place called Horseshoe Mountain. Um it's called that because it's shaped like a horseshoe which is actually kind of part of the story here. Get to that in in just a few minutes. Um, as you pan around in the landscape, you know, the idea of of these initial landslides sweeping up everything in their path and then just routing all of that mud, boulder debris, trees growing along the stream bank and on the initial sliding area and sort of spewing all that out into the valley here in the dark. You you might add sometime in the, you know, kind of the wee hours of the morning.

[00:20:12]It's it's a a very frightening scenario and it's one that though comparable to to what we had with Helen here is is absolutely more intense. Now it's affecting a smaller area. It doesn't have a wind component but you're looking at that total Helen rainfall sort of sort of overnight. um essentially maxing out or or coming close to maxing out the like the atmospheric possibility in in this part of the Appalachin. So, it's a scary sort of thing and it's one that you would expect to happen quite rarely, but believe it or not, in this region, there have been a number of events since this, this was only in 1969, that have produced comparable amounts and intensities of rainfall. uh it just happened to be in areas where where there was less of of a human toll and certainly in this part of the Blue Ridge the the human toll was quite extreme particularly for 1969 about 125 people killed here in Nelson County that was uh essentially one 1% of the whole county's population um certain families in particular uh the Huffman family which been associated with a creek called Davis Creek which is sort back over the mountain from uh from the horseshoe mountain we've been talking about here. Uh about 30 members of that that family were lost in this one event just due to where they were living and and all of this debris flow uh intensity within the landscape. You didn't even have to be in the the steepest and most rugged and and highest parts of the mountains around here to see this really extreme behavior. uh right in the middle of the screen there.

[00:22:01]It's an area that um actually matches up pretty well with with that last part of the sketch there where you've got a a hollow and a spur and a hollow and a spur and a hollow and a spur with uh the the drainages there coming out of it. We can actually kind of sketch our little little streams in there really quick. Right. So, there's the the the drainage network as it is today. But if you look really closely and we'll zoom in on them, you can see all these scars there. Probably going to need a different color. Get something like a brown going on there.

[00:22:34]And see all of these incredible scars that reach way, way, way up into those hollows there and routed all of that debris flow material down here into the stream valleys. uh producing what would have been at at the mouth of those stream valleys just something almost almost unbelievable. And the the interesting thing here is that you don't you don't see any problems up here on on top of the ridges. Um among other things, that's confirmation that what you're looking at here fundamentally is a a landslide event. It's not something like the the rain is focused on one little spot or or something like that because if that were the case, you would see some kind of scarring there in some in some location kind of along the ridgetops. Um that is completely absent and that's something that the early damage surveys here noted. Uh the only places you see the problems are in those hollows. Uh, and that tells you that even though the rain was incredibly intense, the the issue that you're seeing is water soaking into the soil, making it really heavy, reducing its frictional strength. It sort of can't hold on to the rock underneath it or hold on to its itself anymore. It starts sliding and liquefies, and that's where you that's where you end up with sort of the runaway disaster that that we saw here. Um, zooming in on on these headers here. Particularly interesting. We're not uh again anywhere near the the highest and roughest mountains in the area, but that doesn't matter. Uh as long as you have that concave hollow shape and enough steepness, if you put 25 or 30 inches of rain on this in just a few hours, you're going to see the type of uh the type of effect that occurred here on night of August 19th to to 20th, 1969. what what does this look like um in in actual practice? Right?

[00:24:33]So, we can we can see all these scars here. If you end up doing something like, you know, trying to trying to outline them or something here with an appropriate color, they're absolutely everywhere. Um if you had been here after the event, what would you have seen if you had uh you had looked up toward the mountain?

[00:24:52]This is a really incredible one right right there. Um there would have been uh of course very extensive scarring that you would have seen and this event's significant because there is a photographic record of it. Um my colleagues and friends up in the Virginia Geological Survey, they call it Virginia Energy. That's the that's the Geological Survey. That's who's doing geologic mapping and in this case doing the landslide studies. They've done incredible work here just just trying to catalog basically what happened here so that we have an understanding of what the land does during a weather event like this. Um actually got a live viewer here that you can cruise around on. Pink is where a debris flow went. Got a bunch of little yellow points here. That's where debris flow started. Uh and as you zoom that out a little bit there, that's a lot of pink. um literally just about every place where you could potentially have seen landsliding turning into debris flows that did happen with this storm within that very small uh sort of restricted area there in Nelson and a little bit of Alam Marl County. That's what you would have seen uh sort of in in real life. Um, again, no problems up here on the on the crests of the ridges or even up on on top of the mountain there, the uh the issues that you're looking at are all restricted into these hollows. So the scarring would have been absolutely extreme, but man, when it gets down there into the valley bottom and all of that material sort of spreads out, you end up almost sort of like drowning the drowning the valley floor there with boulder, mud, tree, general soil.

[00:26:40]Basically everything on the side of the mountain that was in the way was was going to end up down there in the valley bottom. And the thought of that happening in this pouring down rain at night, people said if you went outside it was actually hard to you like you wanted to cover your mouth because it was actually hard to hard to breathe because it was was raining so hard. So it's um it's an absolutely intimidating to to say the least type of type of disaster event here that again you you'll you'll see something like this again in the Virginia Blue Ridge. Um can't tell when and where. We would see it we would see it coming to some extent today. But the uh the particulars of that of course can't be known until it happens. But you'll you'll you'll know much more about that because in the intervening nearly 60 years our forecasting and ability to watch and and monitor weather is is greatly improved. um particularly interesting aspect of this region and this is something that uh that some of the media here on uh on the Virginia site actually shows really well let me highlight that one in yellow right there is the picture on the left there um looking at this place called Fortunes Cove um more Appalachin terminology call something a cove that's kind of a bigger of a bigger enclosed valley area so you're talking about a flat valley bottom you probably got farming going on in it but it's really really sort of encircled or almost enclosed by mountain ridges. Uh that is a specific detail of this part of the Virginia blue ridge that is really really noticeable. If we bring the uh the colored elevation map back in here and zoom out, it it's pretty quickly clear that you do have specific ridge development patterns uh where a a ridge will come out and and sort of bend around and then keep going parallel to the other one. uh and you actually do end up with um something like you know horseshoe horseshoe type of of shapes um in in the landscape. The horseshoe mountain that we were talking about earlier is uh is kind of hanging out right right there. Right. And that aspect of the land while not necessarily making the effects worse um did sort of concentrate them such that everything was kind of pouring down into the into the same valley. Right? So this was certainly a a situation where a singular weather event and a unique topography came together at night to produce something absolutely incredible, almost unimaginable. Uh and if you went here today and and mentioned this storm, folks will know exactly what you're talking about and they will probably have a lot of stories with it. So hope you found this video interesting. Hope you check out the next one when it comes along.