Salty and I have a rural bug-out location (BOL) and weekend hangout. We’ve been developing it a bit at a time for years. The first thing we did was put in a pond. The next thing that happened was erosion of the banks of the pond. So we tried some erosion control measures. Recently a reader asked for an update on how our attempts have gone. We found some things that don’t work, and one that does.
The pond and its erosion problem
We put the pond in by having a man with a bulldozer scrape a dam into one of the steep gullies that lie between our two ridge-top prairie areas. We’d hoped to have it a little bigger, but ran into some glacial erratics and stopped while we still had a spot that would seal well. That part worked well; while the pond’s a little smaller than hoped it stayed nearly full even during last year’s nasty drought.
It means, though, that we started with very steep, highly erodable banks. The very night after the pond was finished, it was filled by a seven inch rain. We already had rain gullies one day after the dam was built.
It started to rain even as the bulldozer guy finished building the dam. By the next day, the pond was full. The banks were steep, bare, highly erodable clay soil. In this picture, we’ve already started the first erosion control (left side of pic).
The first erosion control attempts
The first thing we needed to do was reduce the force of rain hitting the slopes. We figured to seed at the same time. Our answer was rye grass covered by straw. You can find the full story and our reasons for it here.
These methods were partly successful. Wherever the slope was not too steep, such as the top and back of the dam, the plan worked. The baffles placed in the biggest run-off lanes did reduce their erosion, but not enough. A bale of straw will only stop a deluge down a steep gully for a bit; then the water flows around it and that cuts a new channel.
The steep slopes, especially on the side away from the dam as shown in the pic above, were a problem. The washing force and poor soil were too much for the rye grass and it didn’t establish.
The rye and straw worked on the dam side. On the steep sides, not so much.
Trial two
The next year, we tried a prairie seed mixture on the areas where the rye hadn’t held. These were similar species to what were thriving on the ridge-tops, so we knew they like the climate fine and wouldn’t become an invasive species problem. Also, we thought they’d be ok with the really terrible soil, since the whole place is like that except for a couple inches of topsoil.
Well, those prairie plants Demand that two inches of good topsoil over their clay. They completely failed.
That year we also worked on the gullies. Whatever glacial erratics were on hand got dropped in the bottoms of the gullies (erode THAT chunk of ancient granite, I dare ya!). I also got a bunch of shims and more straw and built a multitude of small baffles in the gullies (instead of the one big one I’d tried the year before). I’d learned they wouldn’t stop the erosion, but hoped they’d slow it down. They did — did fail to stop it, but did succeed in slowing the downcutting of the gullies.
So, some progress, but the steep sides were still an issue.
What finally tamed the erosion beast on the hillsides
Alrighty then … what will grow in northeast MO on bad soil that has a greatly interconnected root system to hold soil? That can stand being on a steep exposed hillside? That won’t make me sad I ever thought of it for erosion control (Did you know that’s how Kudzu ate the South?)? How about some nice red clover?
So I tried seeding the steep hillside with red clover on Spring 3. And…it Worked! Not instantly; it took the full year to get thinly established across the whole slope and has continued to thicken up since. But all the bare soil except the bottoms of the gullies themselves have been covered up. When I poke around under the foliage, I can see the soil’s holding even on the steepest ground (45 degrees). The edges of the pond are no longer crazed by little erosion rivulets yearning to grow into mighty rivers.
This is the same section of steep slope that looked so raw in the first picture. Now the clover’s roots bind together and hold the soil in, as they reduce the force of the falling rain.
It takes no care — which is good; with that steepness it’s a bear to get in there and work it. The bees love it. Clover fixes nitrogen, so it will improve that nasty clay it’s hanging onto. The deer go over to graze it sometimes; especially in late summer when it’s the tenderest stuff around. It’s perennial, so I’m done having to mess with it at all I expect.
A close-up showing that greenery on the tough spots is mostly the red clover.
The other cure is natural. Underbrush from the surrounding forest is encroaching from the top down. Given enough time it would have handled the problem by itself … but the pond would have been half filled with sediment by then.
Here the forest underbrush ins moving downslope. It would have been far too slow to save the depth of the pond though.
Those gullies…
I concede defeat, to some degree, on the gullies. Every year the bottoms get a little deeper but also a little more rocky. The more rocky they get, the slower the erosion cut-down gets. The only way I know to stop it is with Lots of rock; and to be honest the risk of carrying that much rock over ground that steep is not worth the little bit of soil we’re still washing into the pond. There’s no way to get heavy equipment back there without cutting through serious woods or draining the pond — also not worth it. I checked the gullies out yesterday, after getting a ridiculous *foot* of rain last week. It’s officially Good Enough.
Ok, so the gullies aren’t perfect; but they’re no longer gaining depth perceptibly. This is after a foot of rain in the past week.
Outcome
Will the pond fill in with sediment eventually? Sure. That’s what ponds do. Every year farmers have to drain and rescrape some of their cattle ponds, for example. Given our starting depth and the current erosion rate though, Salty and I won’t live long enough to see this pond get too shallow to sustain our fish. The BOL has a dependable water supply and fish habitat. The deer visit regularly. Soon we’ll build a dock to make it easier to dangle our feet in the cool water on a warm afternoon. We like it.