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Flexible depth Swales and TEFA

 
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I was thinking about Swales in general, and had some thoughts about how to build in a little more flexibility in a swale system. Traditional Swales are a ditch on contour with an uncompacted berm on the downhill side. The swale follows the contour, and thus has a consistent depth all along its span.

What about making a swale that didn't Always follow the contour, but would go on and off contour, up and down a few feet, making high and low points in the ditch of the swale. The berm, however, would have a consistent level, so that any heavy precipitation would still overflow though a sill rather than overtopping and eroding the swale.

This approach to building would allow for implementing Paul's thoughts on tefa- having more microclimates and dry and wet spots within the swale, as well as allowing for some artistic expression- rather than being constrained to contour, you can define shapes that you wouldn't otherwise be able to create.

Call it an flexible depth swale, or a TEFA swale, or a hybrid swaledam.

Anybody have any experience with this, or thoughts?
 
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Location: Kansas Zone 6a
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nathan luedtke wrote:I was thinking about Swales in general, and had some thoughts about how to build in a little more flexibility in a swale system. Traditional Swales are a ditch on contour with an uncompacted berm on the downhill side. The swale follows the contour, and thus has a consistent depth all along its span.

What about making a swale that didn't Always follow the contour, but would go on and off contour, up and down a few feet, making high and low points in the ditch of the swale. The berm, however, would have a consistent level, so that any heavy precipitation would still overflow though a sill rather than overtopping and eroding the swale.

This approach to building would allow for implementing Paul's thoughts on tefa- having more microclimates and dry and wet spots within the swale, as well as allowing for some artistic expression- rather than being constrained to contour, you can define shapes that you wouldn't otherwise be able to create.

Call it an flexible depth swale, or a TEFA swale, or a hybrid swaledam.

Anybody have any experience with this, or thoughts?



I think you need to have the downhill edge and base of the berm on-contour but you can easily make deeper wider spots in the ditch--micro ponds.

 
steward
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I've done a lot of digging over the last year and have tried some of what you are talking about. All of my swales are on contour but the height of the berm and the depth vary quite a bit. When they fill there are deep spots and shallow spots. In some places the water comes closer to the top of the berm and in others it's much lower. Also I've varied the width of the berms from a 3 feet wide to 8 feet wide. Gravity pretty much dictated that for me. This has an effect on how quickly the water seeps through the berm (thinner areas get waterlogged faster). In some places the berms have a lot of wood in them. In other places it's almost all clay and stones. Basically, it's a lot of different variables all allowing for different niches to be created. For the most part I'm pleased with the results of my efforts. This is the first growing year for this system so I'll have more info in the fall but so far I can already see differences in the growth of my cover crops. There's also some variance in the species of critters in various areas. Anyway, I would encourage you to try all sorts of variations. The worst that can happen is the berm blowing out, but that can be fixed easily enough.
Best of luck
 
steward
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I have been wondering if you could direct extra water to thirstier plants this way . Acacia and wolfberry at the shallower end , plum and comfrey at the deeper end ?
 
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