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Swale construction

Creating Swales

Surveying and Installation
Monday, July 7, 2014, 4:32 PM

Swales are simply ditches on contour (contour is a level line across the landscape), with the excavated soil from the ditch being placed downslope to form a berm. The purpose is to rehydrate landscapes, add texture and microclimates, and to be used as a tree growing system. You can also use swales to increase catchment for ponds.

Seeding the berm

Most landscapes can benefit from a swale system. There are some instances where it can be counterproductive or even dangerous. An extremely steep landscape with swales could cause mudslides. An extremely wet landscape probably doesn’t need them, although planting up in the berm can help the trees from getting wet feet.

Swales

When I am looking at a design, I want to see a contour map to figure out the possibility for pond and swale opportunities. For swales, I like to find the longest contour line first. Unless it is at the very bottom or top of the landscape, I will probably use this contour line for a swale. I am also looking to use the swales to make connections to ponds, or downspouts, or runoff.

Drain tied to swale

There really is no right or wrong answer as to how many swales, how far apart they should be, how big they should be, or what you should put in the ditches. It is better to look at swales as a tree growing system and a way to rehydrate the land. Put in the type of swales that will best complete your goals for the site.

Swale planted and seeded with straw

I have two different types of swales on my property. I have one system, where I filled the ditch with organic material. The thinking here is that the organic material will feed the trees on the downslope berm. I also have some of these swales feeding a drainpipe that feeds my pond. Then the overflow from my pond feeds on final very long swale. This swale is larger, but the ditch is not filled in. I did not have enough organic material to fill it, and I figured being at the bottom of the property, the soil is more fertile anyway. I have also used the swales as the basis for a food forest, by planting trees on the berms, but also planting downslope and upslope of the swale that will rehydrate that land making it suitable for tree growth. I prefer to fill the ditches with organic material for small swales, but I prefer the open swales in the video “Swales 2.0” for larger swales.

Once you’ve observed, planned, and mapped out your swales, you need to mark the contour lines. I’ve used and ‘A’ frame level and a laser level. If you don’t have a laser level, rent one, it’s worth it. I marked my lines with flags then painted with white turf marking paint. After, I pulled the flags up. Otherwise you destroy them with the excavator.

The next step is to line up your labor, tools, equipment, seeds, trees, and shrubs. I rented a mini-excavator with a 24 inch bucket. This was a good size for my 6 acre property, but if my land was wide open without obstacles, I would have gotten a bigger machine. It is necessary to plant your swales immediately following or even as you’re building the swale. If you don’t dominate the space with trees, shrubs, and complementary groundcovers, other plants that you may not want will take over.

I planted a wide variety of fruit and nut trees and shrubs, as well as a healthy dose of nitrogen fixers, pioneer species, nutrient accumulators, pollinator and predator insect attractors. Your ratio of nitrogen fixers to your productive species depends on what you are looking to accomplish and what type of climate you have. If you are in a desert climate, or the tropics, then you want lots of hearty nitrogen fixers, as many as 15-1. However, if you are in the temperate climate that gets steady rainfall, you can get away with as little as 1-1. It also depends on how much work you want to do. If you’re planning to bring in compost every year and tend to the trees carefully, you can put more productive species into your system, but if you want to put very little labor into your system, you might want to have a higher rate of nitrogen fixers in your system.

If planned well, a swale system is a simple earthworks system that can be implemented with a minimal amount of cost, but yield a tremendous amount of benefits.

~ Phil Williams

Phil Williams is a permaculture consultant and designer and creator of the website foodproduction101.com.  His website provides useful, timely information for the experienced or beginning gardener, landscaper, or permaculturalist. Phil's personal goals are to build soil, restore and regenerate degraded landscapes, grow and raise an abundance of healthy food of great variety, design and install resilient permaculture gardens in the most efficient manner possible, and teach others along the way.

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7 Comments

Oliveoilguy's picture
Oliveoilguy
Status: Platinum Member (Offline)
Joined: Jun 29 2012
Posts: 578
Thanks Phil

Great article. Very helpful. I'm contemplating swales since our property has a dry creek running through it that can become a raging river once every year or two. (We are considered to be in one of the top flash flood areas in the US). Our goal is to trap that moisture on our property, or at least slow it down and give it a chance to spread out and absorb into the subsoil. We have 2 tanks that fill during rains but will only hold water for 4 months during a drought. Texas climate seems to be on the extreme side but the managed land looks fantastic compared to the neglected and overgrazed land. Deer and turkey really appreciate the moisture we provide, and seem to have figured out that we are not hunters like some of our neighbors.

 

Phil Williams's picture
Phil Williams
Status: Gold Member (Offline)
Joined: Oct 14 2009
Posts: 337
Your Welcome!

With large amounts of water coming intermittently, I would recommend large open swales, the bigger the better. I would highly recommend an excavator with a tilt bucket, so you can easily do the front and back cuts of the swales.

Oliveoilguy's picture
Oliveoilguy
Status: Platinum Member (Offline)
Joined: Jun 29 2012
Posts: 578
Hugelkulture

A couple of observations. You have beautiful topsoil.....Wish we were so lucky. Our terrain varies from dark rich soil in our pecan bottom, to outcroppings of rock at the top of the property. You talked about burying organic matter.  Do you think the principles of Hugelkulture make sense? In my case, I think I'm needing very large swales to divert water from the main runoff areas. We have piIes of tree branches and rocks that could be incorporated.  I could see the swales tapering as they flared out toward the flat ground, but starting out 8' to 10' high and very deep. 

Phil Williams's picture
Phil Williams
Status: Gold Member (Offline)
Joined: Oct 14 2009
Posts: 337
Organic Material

Olive Oil Guy,

I like filling the ditches with organic material. This helps to feed the trees growing on the berms, and the organic material holds TONS of water. However, if you don't have a free source of organic material, I don't think it's worth spending a fortune on it.

A couple things to consider. If the slope is steep 18% grade or steeper, I would recommend terraces, not swales. Also, you may want to consider a keypoint dam with swales to pick up the catchment.

You can use the woody material you have in the ditches, or you can cover them with the berm to make hugel berms. I like the idea of the hugel berms if you have lots of wood.

Also, you can make swales by simply placing all those stones you have across the landscape on contour.

Phil

 

Bytesmiths's picture
Bytesmiths
Status: Silver Member (Offline)
Joined: Apr 29 2008
Posts: 220
Turn a sponge into farmland!
We turned a sponge into usable farmland with swales.
 
The plot had been worked by machinery for years, and had a serious clay plough-pan. This caused it to hold surface water well into June in most years. Attempting to work it resulted in stuck equipment and Frankenstein's Monster boot — sometimes lost in the mud when a foot came out.
 
We planned three swales, at 80 centimetre intervals, each with a catch basin. We used a simple home-brew water level to lay them out. A couple neighbourhood urchins pulled the survey stakes before we could finish, but we got two swales in, and the results were dramatic: we could get into that field a full month earlier, and we could delay irrigation by at least two weeks, as the full swales of June continued to water the beds into July.
 
The area below the planned third swale is still a sponge — next year's project.
pyranablade's picture
pyranablade
Status: Silver Member (Offline)
Joined: Nov 8 2010
Posts: 206
Helpful blogpost!

Thanks for that Phil.

 

What kind of perennial nitrogen fixers do you recommend for the berms of the swales?

 

Jeff

Bytesmiths's picture
Bytesmiths
Status: Silver Member (Offline)
Joined: Apr 29 2008
Posts: 220
pyranablade wrote:What kind
pyranablade wrote:

What kind of perennial nitrogen fixers do you recommend for the berms of the swales

How about Eleagnus spp.? Nitrogen-fixing perennial fruit trees!

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