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Using swales in urban yards  RSS feed

 
Pat Rasmussen
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Thank you Toby for being here to answer questions. I'd like to hear creative examples of how people use swales in their urban yard gardens. I've done swales on the large acreage scale but not in city yards. I've read gaia's garden and am reading Permaculture City. On the large scale I got the county contour map to start with. Where do I start for the contours on the small scale? Thanks, Pat Rasmussen
 
Zach Muller
gardener
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Location: NE Oklahoma zone 7a
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bike books chicken dog forest garden urban
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Hey pat, i have had some experience with swales in an urban setting. At my previous residence i had a system of about 5 small swales. They started right at the highest side of the property and stepped down from there. Sometimes in the city you have to make do with being off contour, like for example my highest swale was between a fence and a road. To make the bottom level i had to have it varying in depth since it wasnt quite on a contour line, but it was functional. It saved my parking spots from being washed into my garden, so it was necessary. My others were more on a contour line and that was where i had my main garden.

At my new place i had to start from scratch so i started again at the highest side of the property and went about marking contours above the house. Its a little more suburban even though its in the city center. One of my primary goals at first was to stop surface runoff from hitting the house and flooding the garage. Once i marked the contours i made the trench and made sure the overflow was running past the house and around the side. It started working right off, now i have a lot more time to plan the rest of my earthworks, with this first swale relieving the major issues.

Im sure others will have other experiences as swales in the city has been done a lot. Goodluck.
 
Toby Hemenway
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Pat- Laying out swales in a small lot is pretty easy. The simples and best tool for establishing contour lines at small to moderate scale is an A-frame level, which I've described in Gaia's Garden, and there are many descriptions and videos of how to use them on the web. They are easy to make, just 3 sticks, string, and a weight.

I assume by "swale" you mean that you are wanting an on-contour berm and basin system that will infiltrate water, rather than a drain for moving water away from wet areas. Brad Lancaster's book, "Rainwater Harvesting for Drylands and Beyond" Volume 2 has really good information on how to determine the spacing and depth of swales based on soil permeability, slope, and rainfall, so if there is any question in your mind about how much water your swales need to retain, that can help you figure out placement. It's important not to be dumping water onto your neighbor's yard or to put in a swale that will saturate a neighbor's soil with too much water. Often, swales in urban yards are less deep than in rural places because people are walking around a lot of the yard--unless you can integrate a good path system on the berms. That means more swales, since the water holding capacity of each swale will be less. Or you can make the straw-filled swale that I describe in GG, which is very unobtrusive. The swale can also be filled with woody mulch to make it less of a big ditch, although in large rain events, the much can get washed out of the swale.

Without knowing anything about your rainfall, soil permeability, slope, there's not much more I can tell you.
 
Kelley Burnham
Posts: 6
Location: Concord, CA
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Hi Pat, I have a small urban lot, and I use two swales in the backyard to capture roof runoff. Because of some existing trees and lack of precious real estate, I opted to make my swales and paths one in the same. The swales are narrow and therefore not terribly deep, but they hold and distribute an amazing amount of water. My lot is quite flat, so I was able to dig one of the swales off contour (the bottom is level), and I have backfilled them with the largest wood chips I could find, my reasoning being that the larger chips mightl be less apt to float out, create larger voids for water, and decompose more slowly than small chips. I installed these last winter, and watched them through a few good rains and all worked well, however I'm in CA where the rains have been few and far between. If we do get the El Nino rains this year, they will be tested. Hoping!
 
Joshua Myrvaagnes
pollinator
Posts: 567
Location: Massachusetts, 6b, urban, nearish coast, 39'x60' minus the house, mostly shady north side, + lead.
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Here's my variant question--I have a really narrow path to swale on (if I didn't care about destroying plants, it could go about 6' wide, but I'd prefer not to lose/move the ferns and blackberries that have already been there a few years). On one side is the house, on the other the neighbor's fancy-fancy fence that she is fussy about being damaged.

So I tried an experiment, which I call the "swale-let" or "too small to swail procedure." Just dug pits about a foot deep, and about a foot apart, in a line along the path, and filled them with wood chips. Until I ran out of wood chips and then filled them with some chunks of wood topped with wood chips mixed with earth. I did this mostly because it was the easiest thing to do. If I can get more wood chips I'll do more that way, but chunks of wood are more of a definite. (as a digression, I didn't really believe the woodchip-pile-can-heat-up thing until I reached my hand in a pile about 15-20' high and recoiled because I was about to get scalded! and this was just some pile of city yard waste that no one had remotely tried to make into an intentional heating source!)

The other thing you need to know is that there's a rain drain pipe just above this path area (which runs about 2/3 the length of the house long). I also want the water to somewhat direct downhill to collect in a pond-let and soak into a hugel bed that's, unfortunately, shaded by a conifer--but still doing his job (saving my comfrey from dying. Yes, you read that right, my comfrey was dying until I put it in a hugel bed. Now at least it is fairly happy, and I just have to do a little work occasionally to grab leaves and mulch the trees. Our soil is really weird.) In other words, I want to soak some of the water but it doesn't have to soak super lots because it's needed downstream more than up.

We get supposedly about 40" of rain a year, but this year it was more like 30 or 20 even in parts of Boston. LONG periods where it doesn't rain for a few months and then deluges. Also, this path runs northeast, so it gets the setting sun, and is in fact one of the sunnier parts of the yard. The hugel at the bottom of it benefits from height to get a bit of sun too. The back yard is shadesville, even when you're not under the conifer in the corner, and so we really value that side yard having some berries and some beauty (ferns).

I tried a french-drain-ish ditch approach initially but the soil eroded right into the gravel so thoroughly that it became more of a chocolate chip ice cream. So now I'm trying this other way.

I don't know exactly where the contours are, but I'm pretty sure it would approximate a bunch of parallel lines orthogonal to the path:



x x = frowny-face neighbor
^
________ fence______
|||||||| <path/swale C| C = conifer
_____ H | H = hugelbed
| O | O = pondlet
house| | CHO = Margret Cho
| | |||| = the contours approximately across the downsloping path


The soil under the path and much of the yard is pretty compacted and dark, until you get down 1 1/4 feet and then it's red. The soil on the sides of this path, where the blackberries are, is much softer for at least few inches down, since it's been mulched 2 years now and had a chance to breathe.

There's a small amount of foot traffic on the swale, but not crowds. I need it to be able to double as a low-use path. I'd love to spring for some flagstones that would disperse compaction a bit and also serve a mulching and temperature moderation function and happy worms and crawlies, but so far I haven't scored any flagstones.

Functions:
soak some water to help plants on either side
turn compacted soil into looser
direct some of the water downhill to pond-let and hugel bed
aesthetic -- look a bit intentional like a path, and be feel-able as a path to our blind housemate, so she can walk around the yard knowing where is walkable (vs. trying to mark areas that are unwalkable)

OK, last thing is that the two experimental swale-lets I put in last fall seemed to work OK...it didn't collapse down too much, nor did the wall between the two erode away. The wood chips were moist and hadn't meandered down into other parts of the yard, nor had they broken down much. There were a few happy worms. I had a sense that it would work better if I mixed the earth with the wood chips a bit more, to have a more balanced medium of soaking materials. And since I was running out of wood chips too it made sense.

Any other thoughts? is all this actually accomplishing anything? should I just get a bunch more wood chips and go for mostly woodcihps or is the woodchip-soil mixture better? Thanks!

 
Tyler Ludens
pollinator
Posts: 9741
Location: Central Texas USA Latitude 30 Zone 8
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I think pits or basins work well in small or odd spaces where there might be trees and plants nearby. We've used mostly basins instead of swales. Brad Lancaster goes into a ton of detail about basins in his book "Rainwater Harvesting for Dryland Volume 2" http://www.harvestingrainwater.com/

Personally I would just put woodchips on the surface and let the worms incorporate them over time. Just keep adding more chips each year. If you can get chipped small branches which include leaves, this will be much better for the soil than chips just made from trunks and large branches, but any kind of chips are better than nothing.

 
Joshua Myrvaagnes
pollinator
Posts: 567
Location: Massachusetts, 6b, urban, nearish coast, 39'x60' minus the house, mostly shady north side, + lead.
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Thank you!!! cool, I do have plenty of leaves too.
Tyler Ludens wrote:I think pits or basins work well in small or odd spaces where there might be trees and plants nearby. We've used mostly basins instead of swales. Brad Lancaster goes into a ton of detail about basins in his book "Rainwater Harvesting for Dryland Volume 2" http://www.harvestingrainwater.com/

Personally I would just put woodchips on the surface and let the worms incorporate them over time. Just keep adding more chips each year. If you can get chipped small branches which include leaves, this will be much better for the soil than chips just made from trunks and large branches, but any kind of chips are better than nothing.

 
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