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Stepped Mini-Swales  RSS feed

 
Bob Brown
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Stepped Mini-Swales

Inspired by jack spirko's recent podcasts about food hedges and hearing Paul Wheaton talking about eliminating irrigation. I decided to start creating a food hedge along the edge of our property using as many permaculture techniques as possible while still keeping a somewhat straight run along the property borders.

The use of small wood core beds seemed obvious and since the ground is not flat the use of swales would be nice. However ideal, on contour, swales would wind on and off of our property since the slope varies. In Jack's presentation on permaculture techniques, he talked about slowing water down using swales and about how a sill is used to provide a controlled overflow from a higher to lower swale. That lead to a thought of putting the sill across the width of the swale and having a line of swales at different levels that sort of step down to each other with a sill between them. That would seem to allow me to use swales in a straight line, rather then have them exactly following the contour.

I haven't seen this "technique" before, has anyone used it? Is there a good reason why it wouldn't work?

The picture shows the small swale(s) and woody bed that we built so far. You should be able to see the steps in the swale(s) as it goes down hill. It is probably not very critical in our area (NW CT) most years, as we get a decent amount of moisture (50" rain, 60" snow) and the water problems tend to as much water in the wrong places (basement) as lack of water.

Thought it would be a good idea to get some feedback before trying more of this.

Thanks,

Bob
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Picture of stepped mini-swales - rotated
 
Kris Minto
Posts: 137
Location: Ottawa, Canada -- Zone 4b/5a
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The idea of a swale is to capture water and let it seep into the ground slowing which is why you want to do them on contour. Base on your picture the "swale" is really more of a ditch that will channel the water down the hill and not let it the ground soak it up. Also those steps you put in will quickly get eroded the first decent rainfall you get.
I would dig your swales on contour since you seem to have a slope and you could put in a few rows which offset each other so one will drain into the next one below and not off your property. Have a look at the geoff lawton video to a very good explanation.

Thanks,
Kris
 
Bob Brown
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Kris,

I guess my question was not clear. I do understand the concepts behind swales and their use of contour.

In this case circumstances would not allow for a swale on contour, so something different was needed and wanted to see if anyone had done something similar.

Thanks,

Bob
 
gani et se
Posts: 215
Location: Douglas County OR
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Hi Bob,
I guess I'm still unclear about what you are attempting with your mini swales. Are you trying to slow the water or control its path? If the swale is all sill, it seems like the slowing would be minimal. If you are trying to control the path without slowing it, a french drain might be more effective. You probably already know that a french drain, at its simplest, is a ditch full of gravel. You could drain it to a place where you want the water to soak in (below the basement -- I know about that!) and put a swale and berm at that point.
I hope you'll try again to explain what you are attempting. Even if none of us are doing it, any good idea might prove to be just what someone else is looking for, once they realize what a good idea it is!
Gani
 
Bob Brown
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Gani,

I'm actually trying to perform a normal swale function, capture water and allow it to irrigate the fedge. For normal swales, the swales is on contour and you would have a sill that would direct the overflow into another swales at a lower level (also on contour). Since the fedge runs along the property line, I can not do exactly that. So I thought I would try putting the swale along the fedge (the ground does slope slightly down toward the swale, the ground slopes from far to near and from right to left when viewed from the point where the picture was taken). I doubt I'll ever see an overflow from one swale to the next lower swale (the water seems to always soak into the ground here) but if it did it should flow into a lower swale. The swales are level so they would need about 1" of standing water to overflow - on this ground don't think it will happen.

I imagine that someone has tried something similar, maybe with a different name but I have not seen anything like this so far (about a year into learning about permaculture).

Took a picture from a different angle, but it came out lousy so didn't post it.

Glad you gave an explanation of a french drain, was not familiar with it.

Thanks,

Bob
 
Kris Minto
Posts: 137
Location: Ottawa, Canada -- Zone 4b/5a
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I think I know what you are trying to achieve in the picture you posted. You are hoping to capture water in each of those dug steps and that water will overflow from the top all the water to the bottom as they fill up. Similar to having a series of small dams to control water.

Thanks,
Kris
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Bob Brown
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Kris,

Yes that is it exactly. Maybe a better term would be mini-swales with mini-dams.

Thanks,

Bob
 
Kris Minto
Posts: 137
Location: Ottawa, Canada -- Zone 4b/5a
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I would suspect the first decent amount of rain you'll get will wash away the steps and simply become a small trench which will direct water rather than hold it. I think if it was done on a large scale it would work better but the erosion would still pose an issue.

Thanks,
Kris
 
Bob Brown
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Kris,

A standard swale should have a sill that allows overflow down slope into a lower swale yet as I understand they survive erosion when an overflow occurs. Why would this be different?

We have had several very heavy rain events in the two weeks since I put this in place without problems. I think that is just because of our soil which does not seem to collect any surface water even in the heaviest of rains. Of course that also means that we get at most a trickle of water coming into the mini-swale even during heavy rain. If I ran the output from our gutter and downspout into the mini-swale at the high point, I agree with you that the volume of water would cause erosion and wipe out the steps and the system would become a trench that guides the water downhill.

Thanks,

Bob
 
Bob Brown
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Some pictures from this morning as the rain storm was tapering down. One is a view from above the mini-swale (180 degrees from the direction of the first picture), you can see that ground is moist but no standing water and the swale is moist but no flowing water. The other picture is in the front yard (about 150 feet away) where a low spot that get fed runoff from our neighbor's driveway forms a puddle - that is about as much water as I've ever seen collect in the 18 years we've lived here.

Bob

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Mini-swale from above
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Puddle
 
Morgan Morrigan
Posts: 1400
Location: Verde Valley, AZ.
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I think some chinese farmers do the stepwise flooding thing on hillsides.

They put a piece of plastic over the dams, and mound up the sides to keep em from eroding.
 
Matt Saager
Posts: 48
Location: Oregon - Willamette Valley
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Bob,
I rather like the idea, not certain if it will work for you or not, but the concept is interesting.

It does provide you with one feature a more traditional berm might not in that area, it matches up with your property line and looks esthetically pleasing. That is far more important for those of us in an urban setting than for those more rural.

I would suspect you will see benefit from the design, although probably not as much as from a traditional swale.

Please continue with some updates so we can see how it works.

Thank you for posting the picts.
 
Taylor Brown
Posts: 21
Location: Little Rock, AR 7b
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Bob,

That's a very creative adaptation of the swale. Thanks for sharing. One thing that occurred to me is that you could deepen the mini-reservoirs so that you encourage more water to soak into the berm versus flowing along the berm. In your case, it sounds like you have sandy soil, and yours are plenty deep.

It also occurred to me that one could accomplish similar results by building the berm in the shape of a series of commas instead of a straight line so that the berm itself curves inward periodically to form the dams. That way the interrupted water tends to flow more into the berm plantings instead of down the ditch. The sills would occur at the innermost edge of the comma. (Maybe use a single level patio block.) You might get a more organic looking system with an opportunity for larger plantings in the centers of the comma shape.

Just a thought.

Taylor
 
Roweena Grasby
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Hi bob what you are describing reminds me of a technique used in river restoration. The creation of "pool & riffle sequences" is used along or down a slope as opposed to along a contour and assists with gully erosion etc. Importantly a series of pools or I guess mini Swales are created down a slope, the step down from one to the next is the riffle zone and usually involves the placement of rock or woody material to dissipate some of the energy of the water. The key similarity is the creation of the pools which slows water and promotes infiltration and the creation of micro habitats. Pools and riffles can be designed on varying scales. similarly i think grass swales are used in water sensitive urban design to slow water and promote infiltration. You may find these techniques interesting in expanding your own ideas.
 
Sam Boisseau
Posts: 155
Location: PNW, British Columbia
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Bumping this topic.

I build a 40ft ?? * 8 ft (??) hugel terrace with a swale just below. Turned out the swale wasn't really on contour, but slightly downhill.

So I'm less on a slope than OP and on a slightly longer swale.

I noticed that the water would accumulate towards the end of the swale. I don't think there was that much movement in the water though.



So what I did was divide the swale in 3 parts, and I actually did the REVERSE of the steps on the diagram posted above in the thread. And I put rocks and wood stuff in between the 3 parts. So hopefully this will act as 3 separate swales unless there's some major rain (in which case things won't get too crazy)


The one thing I'm wondering now, is where does this water seep? If you have beds and swales that are on contour, water will move perpendicular to everything which is great. But if everything is a bit off contour I imagine there would be some unbalances as to where the water would accumulate.

Today I was working on a slightly off contour bed, and I ended up putting mini swales (3 foot long) across the bed (on contour) rather than along it.

I would rather have had a bed on contour and a swale the whole way above it, but I guess you gotta adapt when the garden hasn't been built on contour so far.
 
jack spirko
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I like the application what you have is basically a small ditch with check dams to slow the water and cause infiltration to the primary down grade line while moving water across contour. Is it ideal? Nope but it is a solid adaptation. Frankly I am honored that you mentioned me because I had never even thought of this.
 
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