See a row of fruit trees that I planted in 2009. Some are closer or further away from a couple of swales. See the different growth rates based on their proximity to the swale.
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.
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.
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.
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.
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.
See my swale, spillway, and drainpipe entering the pond functioning during a rainstorm.
See how we applied and rototilled the bentonite into the pond bowl. Also, see swales, the spillway, and more pond progress. Incidentally, you will see me track rolling the pond to compact with the excavator. Do not do this if you can avoid it. Get a proper compactor. We used a sheepsfoot compactor, but it had a tough time getting to the top of the walls.
See exactly how to build a large 12 foot wide swale system. I even give instruction on how to use the excavator.
The swales I built last year were done with a mini-excavator. I dug 2 foot wide trenches about 18 inches deep on contour, and then placed the material downslope in a berm. I then proceeded to fill the trench with organic material. This is not a bad way to build a swale, but it was expensive finding enough organic material to fill the trench. Also, I had some erosion of the steep edges. For my new swales, I did not want to purchase organic material, and I did not want erosion.
I decided to build much larger and wider swales to allow for a slope in and out of my contour ditches, and then I would seed the entire structure.
How to Build Swales 2.0
1. Mark your contour lines. I used a laser level to find my lines. I marked the lines with flags then I painted with turf marking paint to connect the flags. Finally I removed the flags before I started digging.
2. Dig a 20 inch trench the width of the bucket on the contour line, placing the soil evenly downslope in a berm, leaving a space for the shallower trench that you will dig next to the berm. I used a 25 inch wide bucket. It is important that you watch the bucket and dig at the same level throughout your swale.
3. Dig an 8 inch deep trench above and below the main trench, depositing the material evenly on the downslope berm.
4. Clean out the main trench to 20 inches deep again, depositing the material on the downslope berm.
5. Run the teeth of the bucket back and forth one time through each shallow trench to smooth out the sharp edges. If you prefer, you can shave the edges by back dragging a tractor bucket. We did this successfully, but ended up with better quality, but a little more handwork just using the excavator. Also, we got the tractor stuck in the trench.
6. Run the teeth back and forth one time through the upper edge to smooth out that sharp edge.
7. Now you are ready for the hand work. Rake the edges and berm so it is even. Make sure the bottom of the trench is level. Some material will end up in the bottom of the trench as you rake the edges to a 45 degree angle to prevent erosion. I ended up with a 15 inch trench. The width of the entire trench was about 75 inches and the berm was also about 75 inches. So I ended up with a 12 foot wide swale system.
8. Make your spillways. You can easily compact an area on the berm every 100 feet with the bucket of a tractor to give you a level spillway in the event of a large rain event.
9. Swales are tree growing systems, so don’t forget to plant your trees. Plant your trees on the downslope berm. I have found that midway up the berm is a good place to plant the trees.
10. Seed the entire system. I used clover as a groundcover mixed with daikon radish, calendula, dill, white yarrow, bee balm, & chicory. This gives me some nitrogen fixation, nutrient accumulation, predator insect attracting, and aeration.
11. Add straw to the entire system. This will get those seeds to germinate, and help the trees with mulch.
12. Initially, make sure the trees are getting an inch of water per week for the first couple of months.
See our continued progress on the pond, keyway, and swales.
See our continued progress on the pond, swale, and drainage.
Comments Off on How to Build Swales (Part 3 Planting)
So the surveying has been done, and good level swales have been dug with the soil placed carefully and loosely downslope from the ditch as berms. At this point it is very important to establish your plant material as soon as possible to avoid erosion, and to soak up the water that will accumulate. I installed my swales late in the fall, and I had not yet purchased my trees and shrubs. I seeded in alfalfa and annual rye just to hold it until the early spring. I ended up being too late, and my germination was spotty at best, so I added about an inch of compost to help protect the soil that was quickly eroding.
This past spring I went ahead and planted the berms. I was careful to plant the trees and shrubs that liked well drained soil mid-slope of the berm, or near the top. For those trees & shrubs that like wetter conditions, I planted near the bottom of the berm. After planting the trees & shrubs, I seeded in my polyculture seed mix, and then added a light covering of mulch. The mulch did wonders for germination of the seed and it really helped to hold water on the berm for the plants to become established. Eventually, the roots of the trees will be able to access the recharged water table, but they need a little help getting established.
Below is a list of the Medium to Large Tree Species I Planted
American Persimmon- Native fruit tree
Alder- I planted the most of this tree, because it is a nitrogen fixer.
Cherry- I mixed common fruit trees, to see how they would do w/o the high level of care in an orchard.
Common Hackberry- Great companion for my walnut trees
Crab Apple- Excellent pollinator for my apple trees
PawPaw- Native fruit tree that can grow as an understory tree
Red Mulberry- Native fruit tree that is very multi-functional
Sassafras- Multi-functional tree with edible parts
Shagbark Hickory- Timber area
White Oak- Timber area
VA Pine- Timber area
Small Trees & Shrubs
Nanking Cherry- Actually is a small plum tree
Comfrey- Fantastic nutrient accumulator, I planted 109 of these.
False Indigo- Great nitrogen fixer, I planted 66 of these.
Goumi- Great nitrogen fixer, I planted 26 of these.
Russian Olive – Great nitrogen fixer
Eleagnus- Great nitrogen fixer
Virginia Rose- Great for wildlife habitat
Serviceberry- Great pioneer species
Alfalfa, Dutch White Clover, Bee Balm, Calendula, Yarrow, Chives, Daikon, Dill, Oregano, Lambsquarters