PERMABLITZ: Swale Building

The Permablitz crew with the finished swale. 

The Permablitz crew with the finished swale. 

This past weekend we held our first Permablitz - a free, informal gathering where people come together to build community, have fun, and learn skills related to permaculture through hands on projects. 

Our goal for the day was to create a raised bed on contour (a swale) to catch and store rainwater, helping to minimize runoff and increase organic matter and fertility in the soil.

We started with a quick overview of permaculture ethics and principles.

While any good permaculture-based project will include elements of many different principles, swales offer a particularly good example of Principle 2: Catch and store energy. This principle teaches that by developing systems that collect resources when they are abundant, we can use them in times of need.

As any gardener or farmer could tell you, water is one of the most important resources there is. We're lucky to live in an area where water is fairly abundant, yet too often we rely on the hose for watering our plants, when instead, with a bit of advance planning, we could have captured and stored rainwater to use instead. One way to catch and store rainwater is through the use of rain barrels or cisterns connected to downspouts. Swales offer an even better alternative. By using simple earthworks, we are able to catch and store water directly in the soil, making it immediately accessible to the plants that need it, and building soil quality along the way. 

So what exactly is a swale? It's a shallow trench, dug on contour, with a berm on the downhill side. Because it is placed on contour (pictures lines on a topographic map), each point in the swale is completely level and perpendicular to the slope of the ground. Unlike typical drainage ditches, which serve to funnel water off the property as quickly as possible, swales slow the flow of water, allowing it to spread out and infiltrate deeply into the soil. The berm on the downhill side of the swale serves as a raised bed, fully watered by the water caught with the swale.

The first step in installing our swale was to find the contour line that we would dig along using an A-frame level. This is a simple process that can be done with basic homemade tools: this video gives a great overview of the process. 

With the contour line marked, we proceeded to dig out the swale (roughly 1' deep x 2' wide, with a 3' wide berm on the downhill side). We had planned to add some compost in to the berm to prep it for planting, but the soil we turned up was so rich and full of worms that we decided to skip the compost. 

Once the swale was dug, we worked to make sure the bottom was as level as possible to ensure even water spread, created an overflow channel, and smoothed over the top of the berm and edged it with rocks to prep for planting. 

Projects like this are really perfect for Permablitzes. With one or two people, it would have taken a significant chunk of time, but with a dozen of us we were done in just an hour and a half! It was a beautiful, sunny morning, and we wrapped up in time to enjoy good conversation over a pot of chili. 

Although we didn't have time to do any planting during the Permablitz, we did get a start on the planting process later in the weekend. 

Since our swale is located on the slope below a very old house, we assume there's at least some degree of lead contamination in the soil. For that reason, we're steering away from planting edibles (with the exception of a fig tree, since convention holds that any lead taken up by fruit trees is captured in the wood).

Instead, we're planting a variety of perennial plants with a focus on visual beauty and pollinator habitat. In addition to the fig tree, the bed will contain elderberry, lavender, echinacea, tansy, calendula, and red clover.

To protect the bare dirt from rain and wind while these plants are getting established, we mulched it with a layer of straw. 

We've now had our first rainfall, and the swale is doing it's job! In the picture above, you can see how the water has collected in the swale and is slowly infiltrating in to the ground. 

We're looking forward to seeing how things grow in the swale this season, and given our success with this first installation, we're looking ahead to adding additional swales on the slope below the house to further combat our runoff issues. 

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