In a recent post, we talked about some things that we were doing to make the most use of our limited and imperfect property. One of these things was the use of “contour beds” as a way to control erosion, effectively capture and retain rain water, and to make the most use out of some awkward strips of land on the north and south sides of the house. We are just in the beginning phases of building some of these beds, so I thought it would be fun to do a series of posts to show how we are doing it. In this first post, I’ll describe briefly what a contour bed is, and how to build an A-frame level (a tool that you can use to map the contours of your property).
So, what the heck is a contour bed? Basically, it is a raised bed that is constructed on a slope such that the bed follows a line of constant, level elevation, or “contour line”. The purpose of designing beds in this way are numerous, but typically have to do with controlling the flow of water. As a rule, water always flows downhill (duh, right ;-), at a right angle to/perpendicular to these contour lines. The idea is that as water flows downhill, it will run into the contour bed and effectively stop its downhill flow, being forced to move slowly along the level uphill side of the bed until it reaches the end the bed, at which point it will begin running downhill again (where ideally you have another contour bed ready to catch that water and allow it to be further harvested and controlled). This provides multiple functions, including forcing water to penetrate more deeply into the soil in and downstream from the bed, preventing soil erosion and nutrient loss, and creating microclimates in the different slopes and faces of the typically curvy beds (depends on the shape of your contour lines). Depending on how important it is to harness, retain, or control moisture in your environment, these can be built:
- simply using fertile topsoil and compost (in areas like ours where there is consistent, plentiful rainfall through most of the year and significant water retention is not a huge concern)
- with level trenches uphill of the contour bed (called a swale, used when large amounts of water need to be captured to penetrate soil and preserve moisture in dry climates)
- with wood buried underneath them (“woody beds”, similar to a concept known as hugelkultur where the wood acts as a moisture sink or wick for the soil in the bed above it, adds to organic matter for micro-organisms in the soil to feed on, and stimulates fungal growth in the soil that is important for nutrient transfer with the roots of plants)
- or any combination of the above.
These have become fairly common and important techniques in the area of permaculture. For our beds, we are mostly going with the woody beds since we have an abundance of dead wood around, and there are purported to be huge benefits for soil health. Here are some more resources on contour beds and woody beds if you are interested in reading more:
Once we decided to use contour beds on our property, one of the first issues that I faced was how exactly I would go about mapping the contour of the land. I thought that it might be pretty easy to eyeball a line that I thought was level, but it turned out to be harder than I thought, with many small dips and bends in the slope of our land. I next thought about using the 4′ spirit level that I use for carpentry projects around the house. Again, not the right tool for the job, as it kept getting hung up on rocks, grass, and other vegetation and was too long to actually connect to level points on our uneven land. After doing a little research, it seemed like the most common tool for determining contour lines was a laser level. Unfortunately, a good quality laser level costs upward of $100, which I wasn’t sure if I was ready to spend on something that I might only use a few times. Finally, I came across the idea of using an A-frame level; a simple tool for determining levels in contour lines that I could build by myself for <$20. I was sold…the boys and I found a few different sets of instructions online and set out to build our own A-frame level. Here’s how we did it.
- 2 – 8′ 2″x3″ pieces of lumber
- 1 – 3′ 2″x3″ piece of lumber
- Drill with screws
- Spirit level
- 6′ of string
- A washer, large screw or something similar to act as a “plumb bob”
- A level surface
Step 1) Take the two 8′ pieces of 2″x3″ and place them lengthwise on top of one another. Drill a screw through both boards about 2′ from whichever end you decide to be the top of the boards.
Step 2) Rotate the connected boards so that the bottom of one board is about 3′ from the bottom of the other board. (This dimension isn’t critical, but it will define the distance over which you will be measuring level…3′ felt like a manageable number to me based on the small distances over which the slope of our land changes. For more flat land, a larger distance, such as 4′-5′, may be more appropriate.)
Step 3) Place the 3′ piece of lumber perpendicular across the two connected boards about 3′ from the bottom of the boards. Again, this dimension is not critically important, but will be approximately where you will be sighting in the level, so make sure it isn’t super low or too high for you to see. Screw this small board into the top of one of the two long boards and the bottom of the other so that it is “weaved” between them.
Step 4) Drill a small screw into where the two long boards are connected to one another. Tie one end of the 6′ string to this screw, and tie the weight or “plumb bob” of your choice (washer, large screw, etc…) to the other end of the string. We chose a large screw that I found in the toolbox.
Step 5) Stand the A-frame level up on as level a spot as you can find so that the string hangs down perpendicular to the small cross-piece of lumber. Place the spirit level on the top of the cross-piece of lumber. Place thin pieces of material (cardboard, newspaper, shims, etc…) under one leg of the A-frame until the spirit level indicates a level surface. Being careful to not move the A-frame, use the marker to make a vertical mark on the cross-lumber where the string crosses it. Turn the A-frame around so that it is facing the opposite direction, and repeat the leveling/marking process. This second step is important, as there may be small differences in how the pieces of wood were assembled that will result in minor differences in where the level line will be.
Step 6) Pat yourself on the back…you’re done! Have your boys hold the A-frame level up to show off their hard work for the camera 🙂
To use the A-frame, start by positioning one leg of the level at the point where you want your bed to begin. Keeping that leg stationary, rotate the A-frame slightly so that the other leg moves up or downhill until the string lines up with the marker line that you drew on the cross-piece of lumber. At this point, the line between the legs should be roughly level. Place a marker or flag on the ground directly below the plumb bob at the end of the string. Now, keeping stationary the leg of the A-frame opposite of the leg that you started with (that is a confusing sentence, but hopefully you follow my meaning), rotate the A-frame 180°, then adjust slightly the position of the other leg until you find a level position (once again, indicated by string lining up with marker on cross-lumber). Again, place a marker or flag under the plumb bob. Continue in this manner until you reach the spot where you want your bed to stop, leaving behind you a series of markers or flags that map the contour line that is level with where you originally started. You might be surprised from how different this contour line looks from how you might have eye-balled it…contours can be very deceiving especially where there is a lots of vegetation or subtle rolls to the land.
I found contour mapping to be kind of addicting…after completing my first one, I proceeded to map out most of the rest our property until I used up the 200 yard flags that I had gotten online. I was nowhere near ready to build the beds yet though, so it led to lots of questions from friends and family about what in the world those flags were for that have been in our yard for 2 months! Oh well…it was a good opportunity to describe what a contour bed was to anyone that was interested in listening 😉
As you can see, building an A-frame level is super easy. Hopefully, you can follow this to build one of your own if you are interested (lots of fun to do with kids that are just learning about drills, screws, and levels). In our next post in this series, I’ll show you how we used this A-frame to map out one of our first beds! Until then, enjoy the beautiful summer weather – it is a far cry warmer today than the day that we built this back in February, as you can tell from the kids gear…brrr!!!