Streams getting shallower?

[Al Agnew]

It seems to be a common complaint that the Ozark streams are getting shallower, the holes filling in with gravel. Those of us who have fished them for a LONG time all know of stretches where this seems to be true. But is it? And why?

First of all, a little history. Early accounts of the Ozarks sometimes described the streams as being rock-bottomed, with no mention of large expanses of gravel. While I doubt this was true for all streams, it had to have been true for some of them, especially those in the deep Ozarks of the White River system. A significant part of any stream having lots of gravel or not is what kind of valley it has, what gradient it has, and what kind of geologic formations it flows through. Some geologic formations have a lot of chert, and so the hills in such formations have a lot of gravel weathered out of the rock. Others have little or no chert, and thus little gravel to erode into the streams. And even if there is a lot of gravel in the surrounding countryside, it doesn't have as much of a chance to settle out in a fast-moving headwater stream, and what gravel there is will be bigger.

As for the valleys, some streams, like the middle Meramec, flow through wide bottomlands covered in topsoil, but beneath the topsoil is a LOT of gravel. At some point in the not too distant past (but the geologic past, not the historic past) those valleys had to be filled up with a whole lot of gravel. This perhaps happened at the end of previous ice ages when the climate was a lot wetter but had been cold enough that there wasn't the same kind of ground cover there is now, and thus more erosion. Then, as the climate settled down and warmed, and vegetatiive cover became thicker, the erosion slowed. Or maybe there's some other explanation, who knows. But the fact remains that at some point a long time ago, some of these streams, actually most of the ones with wide alluvial valleys, had a LOT of gravel coming into them. Maybe the closest parallel today would a stream like upper Black River, with its huge gravel bars and even gravelly bottoms. Maybe at one point a number of streams looked like that.

By the end of the 1800s, however, the great timber cutting of the Ozarks was starting. Look at early photos from various parts of the Ozarks, from the early 20th Century, and you'll see thin, scraggly tree cover. All the timber cutting dumped huge new loads of gravel into every tributary, and into the main streams. Then came a whole lot of further clearing and burning all over the Ozarks as hardscrabble farmers tried to make a living off of poor and impaired land. In the years before the Great Depression, the population of the rural Ozarks was greater than it was in the 1970s! There were a whole lot of people living there then, and poor land use practices were rampant. More and more gravel entered the stream systems.

So by the time of the Depression, the streams were probably in as poor a shape as they had ever been during recorded history. Not only from the gravel choking them, but also from the destruction caused by channelizing them to some extent for the great log rafts, and the log rafts themselves tearing up banks and ripping vegetation off the bars in higher water levels.

The population drastically dropped during the Depression, and the feds took over a lot of land in the national forests, and the hills began to recover, but the gravel was already there. It was in all the tributaries. It was still moving down tiny creeks into larger creeks. And there was all that "old" gravel still buried in the bottoms of the bigger streams. But some of the streams began to heal themselves, especially those which still had a lot of wild land along them.

One would think, in this somewhat more enlightened era, that land use practices would continue to improve and streams would continue to get better, not worse. So why aren't they?

First of all, we have to maybe consider another problem, or series of related problems. Is the base flow of the streams what it used to be? Do they flow as much water during drier times as they once did? The answer is, probably not. Part of it is that overall the last 20 years have been drier than normal, even with some wet years and major flooding. That alone would bring the water tables down and dry up some smaller springs, meaning that less water was getting to the streams in dry times. But then there is the problem of cleared land shedding rain faster that land with lots of vegetative cover. There is more development in the Ozarks that ever. More paved parking lots, more lawns, more buildings. And the use of the land for cattle grazing is probably more prevalent than it has been in a long time, if ever. A pasture grazed down to where it is barely covered with inch-high grass is going to shed rain a lot quicker than one covered in trees or heavy grass and brush. So the rains that come run off faster, and the water doesn't have as much of a chance to slowly sink into the ground and replenish the springs.

So we start out with the problem of less flowing water in dry times. And then there is all that gravel, continually filling in pools, apparently. A singificant part of it is "new" gravel, gravel that wasn't already in the stream bed somewhere upstream. We seldom see how much gravel is coming into the streams from every little hollow and ravine with each major rain event, because the stream itself will be high enough then to continually spread out that gravel over large stretches. But I had it hit home to me dramatically a number of years ago, when there was a localized 11 inch rain over one rather small section of Big River in the De Soto area. Upstream there wasn't enough rain to raise the river at all. So the river entering this section where the heavy rain hit was flowing normally, not nearly enough to move the gravel that was coming into it from every tiny hollow. By the time the river reached the end of this short section, it had risen 6 feet, but when I floated the upper part of the section a week or so later, I was amazed to see huge deltas of gravel (including rocks up to basketball size) at the mouth of every hollow. Some of these deltas went halfway across the river, stretched for 50 feet or more downstream, and were a foot or two higher than the river's normal level. The next good flood spread them all out and the river went back to looking "normal", but that was a LOT of fresh gravel.

Another often overlooked source of "new" gravel, which is really "old-old" gravel, is bank erosion. We all know that once you clear the trees from along a bank, the bank begins to erode, and the erosion usually continues for a long time unless something drastic is done to remediate the problem. Remember all that buried gravel in those bottomlands? It's continually washing into the river wherever one of those banks is eroding.

Those of us who have floated and fished the larger rivers since before the days of jetboat wakes have also noticed that many parts of the channels have widened in the last 30 years or so. Many of us believe the widening is due to the pounding of the banks by the wakes. Yes, floods do a lot more damage than boat wakes in themselves, but the wakes attack a narrow zone at water level, destabilizing it and giving the floods weak points to work on. Take a look, the next time you're on the Meramec after a busy weekend, at the zone of the gravel bars just above water level, and you'll see a layer of clean, loose gravel, that is often a lot softer than the gravel directly above it or that below the water level.

The damage floods do is ALL about weak points to exploit. A healthy riparian zone is little affected by floods; if the banks are well vegetated and the gravel bars undisturbed, even big floods don't erode the banks or move the gravel all that much. Anybody who has gotten a vehicle stuck on a gravel bar knows that the undisturbed gravel surface is somewhat cemented together; it has a crust on it that will often support the weight of a vehicle. But if the vehicle breaks through that crust, the gravel beneath is loose and seemingly bottomless. Well, that crust also resists the power of floods, as well. But a disturbed gravel bar loses that protection, whether the disturbance be in one small layer due to boat wakes, or over a large area due to people digging around with bulldozers and tearing it up with ATVs. Disturbed gravel bars result in a lot more gravel being moved around.

And that's one big reason why gravel dredging is almost never a good thing. It is bar disturbance (and sometimes bottom disturbance and bank removal) on a large scale. It doesn't remove enough gravel to make a difference in the bed load of the stream, but it makes enough disturbance in enough ways to make gravel start moving over large stretches of the stream, not just the area being mined. Next time you happen upon a little section of water flowing over a sand or gravel bed, do this little experiment: Scoop out a nice deep hole in one spot. And then watch what happens. The hole will immediately begin to fill in from upstream. And note that the sand or gravel upstream of the hole, which was perfectly stable before you dug the hole, is now all moving to fill in that hole. Now look downstream. All that silt you stirred up while digging the hole has now settled into the pockets and "pools" below. By digging the hole, you suddenly destabilized the watercourse for a much larger area both upstream and downstream. This is exactly what happens on a vastly larger scale with gravel mining, especially gravel mining in the stream channel. But although in-stream mining is the worst, even bar-skimming, removing just the top layer of gravel off of the gravel bar without getting into the stream channel, means a destablized gravel bar, with the gravel that's left moving with the next flood. I've personally seen several instances of this in the last few years, where a gravel bar was skimmed, and a pool or two downstream that had been there and been stable for many years suddenly fillled in with the next flood.

So, if the streams are getting shallower, it's because of several factors. Too much land clearing, development, pasturing in the watershed dumping ever more gravel into the creeks feeding the larger rivers. The gravel already in the tributaries continuing to move down into the rivers, especially with more and more disturbances to those tributaries--and it seems that every gravelly little creek has ATVs tearing it up and people mucking around in it with bulldozers. Too much bank erosion dumping once buried gravel back into the channel. Too much disturbance of the gravel bars that are already in the stream, never giving them a chance to stabilize and start growing plants atop them. And less water flowing in the streams during dry periods due to water tables dropping from poor land use practices and perhaps less rainfall, while floods are comparatively more frequent due to more and faster run-off with each rain event.

How do we fix it? We can't do anything about droughts. We are unwilling to do anything about boat wakes, poor land use, overgrazing, tearing up gravel bars with machinery. And forget about removing all that gravel by dredging it; you can't remove enough to make a big difference, and the removal makes things worse. There are simply too many facets to the problem, and too many people unwilling to take responsibility for fixing the little things they are doing to contribute to it. I have no answers.

[Justin Spencer]

I agree with everything you said, but when it comes to healthy riparian corridors I have seen them adversely effected by the abundance of 50 year floods that now seem to happen every 5. The flood we had in August a couple years ago really grabbed the leaves on the trees and tore the crap out of what I would call "virgin banks" Some areas were widened by 20 feet in areas that had never seen a plow or chainsaw. New islands were cut, and old islands washed away. These damaged areas now are more prone to erosion than ever and only a prolonged period of no major floods will allow them to heal, but I don't see how that 20 feet of bank will ever come back.

[tho1mas]

Do not worry - the E.P.A. will take care of your concerns.

[Riverwhy]

I think Al is correct in every detail. I appreciate the straight forward and non political tone. I have a little over four decades of experience with the North Fork and the Brysnt and I'm not positive about water flow rates changing but once deep pools now filled with gravel is painfully obvious .

[jdmidwest]

Some of the streams in the eastern part are actually working there way down to hard rock. The solid limestone beds will not eroded much further, so you get long expanses of flat, shallow stream bed. Until some flood event comes along to rip thru it, that is what we will have.

But with most streams, as you float along you will notice bluffs. Many many years ago, water started eroding them, cutting thru them to form what we have today. Most streams carried much more water than they do today. I imagine, there was a time where Missouri was flooded with ice water from glaciers and rains like we have never known. Those carved and scoured what we see today. And they created all of those old gravel beds too.

During the age of the dinosaurs and long before, we were just a shallow sea. We had volcanic activity. We had great marshy areas. The St. Francois granites are evidence of the volcanic activity. The limestone bluffs are uplifts of a great seabed deposit. Coal fields are the ancient marshy area.

Missouri has changed alot over time, I assume it will continue until the sun goes red giant and devours us.

[Al Agnew]

Do not worry - the E.P.A. will take care of your concerns.

Actually, without getting too political about it, you need to get your government agencies straight. E.P.A. has very little to do with regulating such things as gravel mining, and little or no power to regulate land use. The Army Corps of Engineers has more power to regulate such things, since they theoretically have responsibility for streams and rivers. The Corps has never been particularly well known for their environmental awareness or activism, and have mostly tried to abdicate that responsibility...if it ain't one of their lakes or the river running into it, they don't want much to do with it. MO DNR has some responsibility as well, but they suffer from two things...a legislature that would seemingly be happy if they didn't exist, and a general lack of inspectors to watch over things.

But really, this is not an easily solved problem. It has too many facets, and much of what is causing it is not illegal, not obvious, and there are no clear bad guys. There is a basic disconnect between what a bunch of landowners are doing on the uplands far away from the river, or the new Walmart parking lot in some adjacent town, or a bunch of kids running ATVs up and down a dry creekbed, and pools filling in with gravel on your favorite stream. But the connection is there. And some guy or some company digging a little gravel off a gravel bar has to be a good thing, right? Except it isn't.

[Mark]

I would think that the massive clear cutting of timber in the late 19th and early 20th centuries were and still are the main culprits. The loss of topsoil has exposed the level of rock that continues to be washed down the hillsides to the streams and will continue to be washed downhill. The massive clear cut continues to be an irreversible environmental mistake. Agree with all you stated, Al, just think the clear cutting is the primary culprit.

[Brian Sloss]

The higher frequency of floods has made some shoals on the 11 Point wider and shallower for sure. I've noticed that over the last 11 years for sure. You really notice it during dry periods. I pretty much agree with Al's original post.

[Al Agnew]

Floods are kind of a bad thing/good thing. While big floods can do a lot of damage to streams, they can also blow gravel completely out of the channel and scour out deeper pools. A lot of times, smaller floods are worse, because they move gravel around just enough to take it off disturbed gravel bars and dump it into the next pool downstream. I believe that the big floods bringing a lot of new gravel into the stream is as bad as the old gravel they move around. But there's no doubt they can also tear up banks and widen the channel.

[Brian Sloss]

Floods are natural and change the river, sometimes good in areas and bad for another, but the frequency is higher now and it is widening the rivers from what I can tell.