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bkbying89

Sand everywhere.

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Checking out the Montauk State Park site had some pictures of the flood and the damage caused by the flooding. I have a question. Where does all of the sand come from? Is it washed down of the hills or is it flushed out of the springs? It seems to be as thick on the ground as it was after the last flood.

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29 minutes ago, moguy1973 said:

It's probably scoured out of the bottom of deep holes where it's been deposited or just everywhere in the river in general.

After the last flood, the sand was everywhere downstream. I was amazed at the amount and found it hard to believe all of that sand washed out of the hills and the uniformity of it made me think it had been flushed out of the spring. There seems to be an awful lot of it. 

Thank's

Bill

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Nope, not much sand comes out of the springs.  Why would it?  Though the springs themselves have increased flow during huge rain events like this, it's not multiples of their normal flow, so it wouldn't wash much out of the underground caverns through which the springs run before emerging.  The geology of the upper end of Current River makes all the sand...Pigeon Creek, which in reality is the headwaters of Current River, is the creek above the springs at Montauk, and it actually has a fair size watershed that is almost entirely within the Roubidoux Sandstone geologic formation, if memory serves me correctly.  That's where the sand comes from.

You would be amazed at the amount of sand or gravel that comes out of every tiny tributary branch, creek, and hollow in this kind of rain event.  It was driven home to me when there was an incredible localized rain in one small area surrounding Big River between Mammoth Bridge and Browns Ford.  This happened a number of years ago...in central Jefferson County only, there was a big storm that just sat there and dumped rain for several hours, more than 10 inches of rain.  The river upstream from Mammoth Bridge got almost no rain.  So above Mammoth Bridge, the river stayed at normal flows, but there was so much rain in that one small area that by the time you got to Browns Ford, only 10 miles or so downstream, the river had risen 6-8 feet.  I floated the river through that stretch a couple weeks later.  Putting in at Mammoth, the river looked normal.  But about two miles downstream, I started to notice "deltas" of sand, gravel, and even good sized rocks fanning out from every ravine and tiny creek coming into the river.  Some of these deltas were larger than the average living room, and two or so feet higher than the normal river level.  It seems that the river wasn't flowing enough water yet to take all this material being deposited by the myriad of hollows and move it downstream, as it does in a normal flood, so they just built up at the mouths of each tiny tributary.  But as I got to the lower end of the float, I noticed that these deltas were no longer present.  By that point, the river had risen high enough during the big rain to pick up all that material and spread it out through the channel.  But those first few miles were a real eye opener as to how much sand and gravel enters rivers from every hollow, ravine, branch, rill, and creek when you get a big rain.

And when you get a really big flood, it does scour out the channel in many places, and deposits the stuff that was in the channel out in the bottomland.  A small flood, one that just fills the channel to bank-full or a little higher, just moves sand and gravel within the channel, and often taked the gravel off a gravel bar and dumps it into the next formerly deep pool.  But a really big flood can pick up all that material in the channel and lift it completely out and into the bottoms.  Pigeon Creek above Montauk has a sand bottom, and a lot of that sand, as well, probably got picked up and moved down into the bottoms at Montauk and below.

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As the current begins to subside after a flood the smaller particles are the last to settle, so it's typical to have sand on top of gravel, and gravel on top of larger rocks.  Less dramatic rain events afterwards will wash the sand downhill, leaving gravel and larger stones behind. 

Billions upon trillions of tons of sand in the Missouri and Mississippi rivers, and it all comes from the smaller tribs. 

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Thanks' Al and Wrench for the lesson in Hydrology. I had read that before all of the trees had been cut along the Current that it had been a much deeper river just because the rain didn't wash all of the gravel into the river. Had you heard of this and to your knowledge is it true. I have to admit I have floated a great deal of the Current but never really studied rivers as living things. 

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If you go by the law of gravity and erosion then the further down a river you go from the headwaters the smaller the stones should be.  This would undoubtedly be true and obvious in a canyon river with no other sizable tributaries.

No doubt in my mind at all that clear-cutting the hillsides caused an enormous amount of dirt and gravel to fill in the rivers.  You'd think though with new growth on the hillsides now that enough floods had happened since the logging days to clear them back out.  Eventually I guess it will....or should.

I don't think the rivers were ever down to solid bedrock though.  Hillsides erode to a degree whether they are covered in growth or not.

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If you read some of the old accounts of the rivers, including the Schoolcraft account, some of the rivers, including parts of the White River, WERE bedrock bottomed in many places.  But I'd agree that most probably weren't.  Clearcutting and then repeated burning of hillsides "to make the grass grow and kill the ticks", as the old Ozarkers said in justification, certainly put a huge amount of gravel into the streams, and I think it's possible that the forests were permanently changed as a result, and are still more likely to erode gravel than they were before European settlement.  The old accounts speak of savannah-like conditions in the forests, with big, widely spaced trees and heavy grass growing beneath them, and that grass would have stabilized the hillsides as much or more than the trees.  Now we have smaller, closely spaced trees with relatively little undergrowth, and the lack of thick undergrowth may be allowing quite a bit of gravel erosion to continue.  More likely, though, is that there is simply still a vast "reservoir" of gravel in the beds of all the tributaries, which is still gradually making its way to the bigger rivers.

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I also remember reading old accounts of the old growth forest of huge pines and the bed of pine needles on the forest floor that kept the undergrowth down, making for easy travel thru the forest, or at least easier than it would be today. Made sense to me.

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