Movement of Water Above Ground

Every watercourse carries both water and sediment.

Practical

My son, who has a Masters in Geology, says a professor told his class it is not worthwhile to try to influence movement of water by bank stabilization, dams, etc. This may be true in the sweep of geological time, but it is not true in the time span of our life. We can make improvements that earn enough more to pay for themselves and benefit us in just a few years. Some of the things you can do above ground (when allowed by law) follow.

The only practical way to preserve a bank where there is cutting on a high gradient intermittent stream is to place stones too big to be moved by the highest flow. We are fortunate to have rocks available on our farm, but it is a hassle to move them from the strip job to streams. I have carried them down when I return from feeding, taking weeks to complete a job, one rock a day.

The creek is, by law, owned by the State of West Virginia, as are all “navigable streams.” This is interpreted as any stream that is not intermittent (does not dry up). Navigable streams are nominally under control of the Army Corps of Engineers. This goes back in common law to a time before the U. S. was a country. The king owned the streams in England. When the American Revolutionary War occurred his ownership fell to the government of Virginia, and when West Virginia broke away, it got the stream ownership. You control the access to it only, but this allows you to keep trespassers out, including fishermen and gas companies who want to pump into their tank trucks or dump out of them.

Presently we have a stream bank erosion plan registered with the U. S. Corps of Engineers and the Soil Conservation folks. You cannot have a (formal, by law) stream crossing without their consent, but we are likely the only farm on Jesse Run (10+ square mile watershed) which does. Other businesses must have one, too, such as a gas company. Materials are not to be filled in or removed from a stream or wetland. Legal use of creek gravel is a thing of the past.

At one time Soil Conservation Service was into straightening streams in a big way, 50 and more years ago. The big stream across from our house had been straightened and put against the south wall of the valley not too long before we came to Jesse Run. John Kolb’s creek (the farm adjacent to ours) had the one big bend cut off, too. If you study the fields, you can find several courses water took in the past. The stream up by the coal road had been straightened, as has the one nearest our house.

There has been an effort to keep cattle from going into steams by conservation interests, because they degrade the banks, and muddy the water. Streams are a great place for cattle to get water, though. What they want you to do is to build watering troughs and fence cattle away from steams. That may be possible for main streams, but not feasible for intermittent streams such as the three that flow south through our property into Jesse Run.

These smaller streams will have a number of crossings. Check dams below the crossings will help to stabilize them, and you may have to maintain a few additional check dams made of rocks, to stabilize these streams. Keep one point along the top of check dams below he surroundings, and let the edges come up to or slightly above the steam bank. Slope the downstream side and/or allow impact of the stream at high flow to hit rocks so the check dam will not be undercut. Go for several small ones, rather than few large ones. Watch and maintain them – usually little is needed.

Where cattle run through heavily used lots you can use rocks in another way. Cattle don’t like to walk on rocks, so you can put large rocks along the streams to control where they walk. The lot where we keep heifers has a stream quite close and parallel to a fence. We place rocks about a foot or so in two dimensions between the fence and the steam to keep them from mashing in the bank between the stream and the fence.

Try using a few piles they won’t want to walk over (one rock thick) every fifteen feet or so perpendicular to the fence and the stream, just so they won’t walk along the fence. If this doesn’t stabilize the banks in some places, you may have to fill piles at shorter intervals.

Particular attention will have to be paid in some areas. We have a stream behind a concrete block well house in the middle hollow, because it is in a very high traffic area. Loss of the block building would ruin a very expensive watering system, which is quite important in a dry year. If it starts to wash, we will build up the watercourse with large rocks so the wall remains intact. The entire channel can be lined with rocks, which is called rip-rap, and you may have to do that in such a location.

If you build a culvert, stabilize the down stream side by using rock or some other method. You don’t need to stabilize the upstream side unless it is quite high. Water piles up against it in times of high water but has little effect. If water flows over the culvert, however, it washes out the fill on the lower side where it splashes over the steep slope, and can make the culvert impassable.

There is a sedimentation basin in one of our small streams near the creek. This is to catch the considerable amount of sediment that comes from the hill. It needs to be cleaned out and the sediment transported every second year or so. We should also have one in the other small south-flowing streams, but there would be some considerable expense in cleaning them and transporting the sediment to some appropriate place. Sedimentation basins should be fenced off to keep the cattle out of them.

Drainage of storm water in small areas is best accomplished by a grassed waterway. The idea is to maintain a broad shallow area that is well grassed over. The grass will contribute to removal of suspended matter, mostly clay and organic debris, from the drainage area above it.

However, if a continuous stream runs for days, several times a year, a channel will develop. This can further develop into a gully if not controlled. Trees along the stream are the easiest control measure. Usually you find them in place. Just don’t remove them. If it is necessary to establish them, Sycamores are a good choice. Willow is easy to establish, just make cuttings three feet long abut the size of your thumb and stick them in place several inches down where they can get plenty of water. I don’t like willows as well as sycamores because they are more difficult to control and the wood is never of any value. Sycamores can be cut and the roots will sprout up again.

Farm roads are a largely ignored area of erosion. Crushed rock is the only real answer. Sometimes you can pick up small rock in your fields, helping both the place where the rock comes from and the place you put it on the road. Water must not be allowed to flow down the road. It washes away the rock and makes gullies. The answer is breakers. Get a technician to help with this. The grade of the breaker and distance apart depend on the grade of the road, and what area drains into the road. The breakers should drain onto established grassland, preferably not too steep. Expect the sediment from the breaker to build up a hump where the breaker ends. Sometimes this becomes too large to allow proper drainage, over a period of decades. In this case the hump must be removed or a ditch maintained through it.

The lower side of a breaker requires special attention, especially if the road is used frequently. If you use the bulldozer to maintain it, and there is plenty of rock, you can push up a lower side of rock. If you don’t have the opportunity to do this put some rock in place, cover it with plenty of dirt and add more rock, building up until you have a pile of rock and dirt well mixed large enough so that it will be high enough to control the flow when it settles. The dirt is necessary to seal the water into the breaker and to keep the rock in place. The rock is necessary to prevent wheel tracks from draining water through the breaker.

The objectives always are (1) to slow the movement of water, (2) to hold the sediment in place, and (3) to prevent gullies and minimize loss of top soil and fertility.

You don’t have to speed up the runoff of water. It can find its own way down hill very well, thank you! When it does speed up, it takes solids with it, and you have erosion.


Descriptive

Streams of intermediate gradient, such as one sees away from the mountains, are a series of pools, each empting into the next. These pools are formed in relatively erodable material, clay or loam, with some smaller rock. The lower end of the pool is blocked by coarser material and the water flows rapidly down a shallow course over riffles into the next pool. This coarser material is sometimes brought into the main stream at the riffles by a smaller side stream with higher gradient (slope) and sometimes it is deposited by a change in direction of the stream. Bars and riffles are constantly changing shape, in large part due to rocks moving down stream. Rock size is an indicator of how fast the water flows over the riffle. Bigger rocks in a deposit mean faster water, because the smaller ones have washed on down stream.


In central West Virgnia all our small streams are high gradient for their size, and are inherently unstable. Over a period of geological time (a very long time) the stream has flowed everywhere between the valley walls – that movement defines where the valley is. Changes in the position of streams come very rapidly, and may seriously disrupt your fields, leaving places you cannot get to, or small irregular fields. In the mountains, where there is a high gradient and sufficient water supply, streams may have a rocky bottom even at normal rates of flow. The sediment in streams, and the deposits along streams may include larger, rounded rocks which have moved some distance. They become rounded by bumping into each other, generating smaller pieces. This rounding down process ends with sand. Sand particles are of such size that in water surface tension of the wetted surface acts as a bumper to form a limit beyond which the size of the particle can not be reduced by bumping. (Very fine grained sand is formed by wind in deserts). Smaller particles in streams are formed by chemical action only.


A basic principle is that in going from a higher level to a lower one, water must dissipate energy. The amount is directly proportional to mass of water moving and distance it drops vertically from one point to another along the stream. At normal flow this is little, but in flood stage it is immense. The stream dissipates this energy by extending its length. It does this by developing meanders (bends). It also dissipates energy by warming the water, but so little you can’t measure it. Loss of energy also happens when the water goes over a falls or riffles, and when it rubs on the banks and bottom or hits other obstructions.

For emphasis, let me repeat, a stream is not uniform in cross section, and does not have uniform grade from higher to lower levels. Considered in the vertical dimension, it is a series of pools, deep quiet spots with riffles between. These riffles are often locaterd where rocky sediment is washed into the main stream by side streams, but appear elsewhere, too. Also, looking down from above, the pools at high flow are not identical with the pools at low flow, riffles having less effect at high flow. Any cross section varies when the water becomes deeper with higher flow.

Changes in the course of streams come at high flow. Double the speed of the flow and the size of rocks that it can move increases by the fourth power (x = awE4 where x is the rate of flow of the steam in any convenient units, such as feet per second, w is the mass (or weight) of the rock and a is a constant relating the units of flow and mass). This relation between rate of flow and mass of the rock that can be moved is one of the highest power laws in nature. The rocks moving at the bottom of the stream abrade (sandpaper) the sides and bottom of the stream. The rocks are more dense than the water (rocks are typically 2.8 times as dense as water), and so are more affected by force of movement (inertia) than water.

Any place water gets up over the land at high water, deposition takes place. If the water is slow and shallow, deposition is slight, and the particles are fine. The presence of grass or tree growth helps deposit solids, because it slows the flow and catches debris. If the water is a foot or two deep, deposition can take place rapidly. I have noticed a lot of sand deposited in some places where it must have been suspended two feet above the low flow level. Notice the elevation of the banks of a stream. I take this to be the equilibrium condition between erosion by the stream propelled sediment on the bottom and the deposition by high water on the surrounding land. Much of the finest sediment, however, goes all the way to the ocean, where the salt water causes it to loose its ability to stay suspended. Deltas (like the Mississippi delta) form where salt causes the suspended small particles to fall out.

If you observe carefully at normal flow, you notice that the outside of a steam curve (the side the stream is thrown against, the cutting side) is vertical, and the other side is slanting from the field level down toward the outside. The outside is being cut away at high flow. Vegetation is an effective barrier to cutting, if it extends to and below the bottom of a steam. Trees are the most important controllable influence on movement of banks. Keep the banks relatively clean, let trees grow where you want the bank to hold, cut them out where you want the bank to be removed. The catch to this last is that the roots do the holding, and they last for years before they rot away, so you have to anticipate, and not let trees get big where you don’t want them. You have to watch the stream banks and cut trees when necessary. It’s an art, not a science. Due to the present environmental-political understanding, it’s best not to cut a lot at a time, especially big, conspicuous trees. The environmental-political group don’t care if the stream changes course and ruins you bottom!