Using Swales in the Landscape Part 1

Last weekend we hosted a group of 19 students for a class about catching rainwater in the landscape. It was cozy – we set the record for the number of people in our basement at one time, and we ran out of chairs.

Though we tried to keep Molly the social cat outside so as not to bother any non-cat people, she just ran back in with every new visitor. After all, it was cold outside, and all the people were inside! Non-cat people were very patient with her weaving her way through the crowd and running in front of the screen, and we love you for it.

Darn it if we didn’t get any pictures. If you got any, we’d love a copy!

We hope to be able to invite everyone back in the summer to see the front yard rain system working, when it’s not buried under ice and snow.

The class focused on two ways to hold rainwater in the landscape: Swales and rain gardens.

In this post, I’m going to elaborate on swales: what they are and why you should have one.

In part 2 we’ll discuss how to build one.

What is a Swale?

A swale is a shallow trench dug out dead level along the land’s contours, with a berm on the downhill side.

Slow it, Spread it, Store it

Slow it, Spread it, Store it. Image courtesy of

In the above picture, the contour lines are shown in pink. These indicate that everything along the same pink line is the same height above sea level, and in this picture, the hillside slopes downward toward the bottom right corner of the image.

Without the swales, the water would form gullies and rush down the hillside without sinking in, taking precious topsoil and nutrients with it.

Swales are dug along the (pink) contour lines and are shown in blue. The soil from the trench is mounded on the downhill side of the trench and planted (shown in green). The important function that swales perform is to slow down the water, spread it along the contour, and let it slowly sink in underground, rather than above ground as in runoff.

Now, the above picture is showing large swales on a large farm field. Lucky for us that swales are also applicable on a residential scale, and our environment desperately needs them. We can all do our part with this simple technique.

Also lucky for us, we don’t need a hillside for a swale to be useful.

Why you should have a swale in your yard:

  • Swales mitigate stormwater runoff.
  • Swales are way easier than catching rain in a tank or barrel.
  • Swales are more efficient than tanks or barrels.
  • Swales build self-sustaining ecosystems.

Let’s elaborate.

1. Swales mitigate stormwater runoff.

Stormwater runoff is a huge problem in most cities. Water is seen as a liability (flooding) so the modern mindset is that we need to send it away as fast as possible. This has resulted in horrible breaches of environmental stewardship every time it rains, when we send 13 million gallons of raw sewage into local waterways each year in my city alone, because the overtaxed combined overflow system combines stormwater with sewage during heavy rain events.

Combined Sewer Overflow. Image courtesy of

Combined Sewer Overflow. Image courtesy of

We think stormwater is a problem that only governments, institutions, and experts can solve. In reality, there would be no problem at all if citizens did their part.

“Though the problems of the world are increasingly complex, the solutions remain embarrassingly simple.” – Bill Mollison, father of permaculture

For example, our 1200 square-foot house catches 30,525 gallons of rain from the roof each year. How much water does your roof collect? We capture 75% of that, or almost 22,900 gallons in our landscape. What if we all caught tens of thousands of gallons of water in the landscape?*

*Assuming a site assessment proves a swale to be feasible

It would mean that the millions of dollars of taxpayer money currently going to fixing the sewer problem wouldn’t be necessary. Quick everyone! Dig a free swale!

2. Swales are way easier than catching rain in a tank.

I wish I had building and engineering skills. Alas, I do not (though I’m always up for learning – Vince humors me). Catching rainwater in tanks or barrels means that you have to buy a bunch of parts. You have to connect the downspout to the container, you may have to connect more than one container together, and you have to connect the overflow either back to the sewer, or run the overflow elsewhere.

You also have to be able to clean out the barrel frequently and add mosquito dunks, and you have to have a spigot for filling up a watering can or running a hose. Plus, all of these parts are going to eventually degrade with sun and weathering and will need fixing or replacing.

And finally, there is very little water pressure from rain barrels, so using the water is quite frankly a pain in the ass. Unless you want to buy a pump, which is fine, but look at all of this engineering and purchasing, when in the end…we could dig a trench and let nature slow the water, spread it, and store it for us. Easy-peasy (after the trench is dug)!

One more thing, if you’re going to have rain catchment containers, the overflow must be planned. Water is powerful and it is both irresponsible and a waste to send thousands of gallons of water to nowhere in particular.

This is the reason why government and experts haven’t been proactively encouraging rain catchment: It just takes one person catching water irresponsibly to flood their neighbor’s basement or start a mosquito pond to ruin it for the rest of us.

So let’s catch it in the landscape responsibly and use it to our advantage.

our rain barrels with walkable creekbed overflow

our rain barrels with walkable creekbed overflow

Inside scoop: We do have rain barrels in addition to a swale and two rain gardens on our homestead. But truthfully, I find it difficult to use the water in the rain barrels in a timely manner because in doing so, I’m spending my precious time hand watering. Our in-the-ground solutions work better, last longer, and save me time.

3. Swales are way more efficient than tanks.

Good soil is thirsty. Organic matter acts like a sponge, easily holding several times its weight in water. Toby Hemenway in Gaia’s Garden tells us that three quarts of dry soil can easily hold one quart of water. When we translate that to the soil in our yard, if our yards were covered in one foot deep of rich, moist soil, it would hold as much water as a 3-inch-deep lake the size of the yard. It would be cost-prohibitive to install a container that could catch that much water. But the soil will hold it for free.

Here are a couple of other strategies that will maximize the benefits of the swale, minimize evaporation, and minimize your time in the garden:

  • add organic matter (compost) and mulch to your beds and swale berms continuously
  • shade the soil on swale berms with dense plantings
The berm of our swale is densely planted with strawberries and flowers.

The berm of our swale is densely planted with strawberries and flowers.

4. Swales build self-sustaining ecosystems.

An underground reservoir forms, and water is released as needed.

An underground reservoir forms, and water is released as needed.

Swales catch water and direct it to where it’s needed, which is in the soil. Instead of water running off or pooling above ground, swales direct it downward into an underground reservoir.

Nature has its own built-in, self-regulating system. When water is needed, it is naturally released. No work on our part after the swale is built!

This underground reservoir attracts microorganisms. Suddenly the soil is alive and the “micro herds” begin eating and pooping and procreating (perhaps not in that order) and voila – we’re generating our own organic matter and fertilizer.

This means fewer inputs on your part, which saves you money and time. The more the organic matter builds, the more moisture it holds. With more organic matter, the system can better withstand both floods and droughts.

As the water reservoir and nutrients in the soil build, gardening will become a breeze for you.

Now your ready to learn how to build a swale!

Have you built a swale on your property? What benefits have you noticed?

This article was shared on Green Thumb Thursday, the Homestead Blog Hop, and featured at the Backyard Farming Connection Hop.

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  1. Beth says

    I assume experience with your property informs you about where the swales should be dug. It’s something we should be paying closer attention to. Thanks for the post, Amy. I look forward to Part 2.

  2. bobbi says

    I just found your blog via Commonsense Homesteading, Thanks Laurie! Anyway, I love this post. I am in Florida, however, and the land is pretty much flat, lol. Would I just make ‘canals’, lol or build up the growing areas? Or would it even matter? Thanks, looking forward to reading your blog and seeing the pictures of your gardens. :)

    • says

      Hi bobbi,

      Thanks for visiting! I’m wondering what kind of soil you have where you live. Is it sandy? If so, you’ll want to make sure your swale is directly on contour. You’ll find contour on both flat and hilly land…all water drains somewhere. In sandy soil, you’ll want to make sure the berm is stabilized.

      Using logs to line the berm and make it look like a raised bed would be a great way to stabilize it. The logs will decompose over time and add fungus and organic matter to the planting area. Plant the berm right away with deep tap-rooted plants like alfalfa, red clover, chicory, dandelion, and even tap-rooted trees like pecan, black walnut, white oak, or basswood. The taproots will help hold the soil in place.

      Best of luck to you :-)

  3. says

    Thanks for this – really helpful! I have a steeply sloping yard on the edge of a ridge so we get loads of run off. I’m
    just now trying to figure out how to best use it. The area I would be most likely to build a swale is in heavy shade – any advice about how to stabilise it without easy access to sun loving plants? Thanks!

    • says

      Hi Nicole,

      Shade-tolerant plants for the swale berm:
      Trees: sugar maple, paw paw (although may not fruit in shade)
      Shrub: spicebush
      Herbs: ramps, columbine, aster, ginseng, ferns, Solomon’s seal, some chickweed

      If the yard is really steep, say 6 degrees/10% gradient or steeper, a swale might not be the best option because it could potentially destabilize the hillside. Instead, consider check log terraces .

      Good luck :-)

  4. Karen Martin says

    Love your ideas. I use a water tank to collect water. I will have to read and study your information. One more thing, please keep your cat inside for the protection of other wildlife. Thank.

  5. tom says

    i am sold on swales already but can’t seem to find a decent contour line. My property slopes North – South (major) to the road and EAST-WEST (minor) toward the driveway. Naturally the driveway acts as a berm chanelling massive amount of water and topsoil into the ditch. Is it advisable to dig a level trench 6 inches deep on one end and 1 1/2 foot deep on the other end? Naturally the overflow would ideally be on the uphill side.

    With three acres and 40+ inches of rain we loose tons of water and topsoil. That is over 3.5 million gallons of water i want to keep. Granted i don’t lose it all but i do lose a significant amount especially during 2-4 inch rain events.

    • says

      Hi tom,

      It sounds like your site is a bit of a challenge. Oftentimes we think of swales as being relatively straight or with a minor curve. However, sometimes like a meandering stream they can be quite wavy or zig-zaggy to accommodate a contour line.

      It’s a challenge to give specific consultation without seeing your property, since what I envision from your description may not be what actually is. You’re thinking well to want to catch and slow the water coming from your driveway.

      I would do my best to try to find a contour line – however wavy or zig-zaggy – because that will allow you to catch the most water without causing problems. If that isn’t possible, you could use a conveyance trench to “convey” water from the driveway to a swale dug on contour nearby.

      As an example, check out the plans of our front yard rainwater catchment project, in which a conveyance trench moves water from our downspout into our front yard swale.

      If you intend to dig a “swale” not on contour and level it out manually, a good safeguard is to put a rain garden in on the low end to capture any excess. It’s a good “just in case”, and is what we did in our front yard. Hope that helps.

    • tom says

      … like a very busy summer for me. Fortunately I have a good source of cardboard and grass clippings plus several cords of wood to build up the berm. Living on a major rural road I also have annual access to power line tree trimmers to add tree mulch to dug out areas. Probably let it mellow a year prior to mulching the berm. In the meantime clover and beans until time to plant tree guilds.

      Once again thanks for the help.

  6. says

    I am really looking forward to building a couple of swales in our new orchard. There is a perfect contour slope that will make for a fantastic swale/berm area, and I can’t wait to get it started as soon as the ground thaws this spring! Thanks for sharing at the Homestead Blog Hop this week!

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