Swales
When I first started gardening on Backfill Hill, I was in such a hurry that I didn’t give a thought to layout. I didn’t take into account Maryland’s torrential rains, or the packed rock-like soil, or the steep slope. I should have – native to California’s hard-baked desert clay soils, I was well acquainted with washout, erosion, and flash flooding – but I was so eager to start gardening right this very minute that I just did what was fastest.
And it’s not like it didn’t work. I mean, it was still soil and stuff grew, ish, at least in spring. Things went fairly ok.
But back then I had no idea how important mulch was. The erosion was continuous. I was constantly having to put more woodchips on the upper paths. All the compost ended up at the bottom of the bed, while the soil at the top was still naked backfill clay no matter how many amendments I worked into it. Hard as a rock between rains.
Even weeds struggled. I ended up just largely ignoring that part of the hill, as its yields were nonexistent.
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With nothing to hold it back, water drains off too quickly, taking topsoil with it and leaving behind naked soil open to erosion.
I knew from the beginning that one should across the hill slope and not along it, but I’m just too impatient. I usually end up having to go back and redo things the right way later, when I realize that jerry-rigging it just ain’t gonna work. And that’s what I had to do this time. All the water that was running off that hill could have been percolating into the soil for the last 6 years, nourishing plants and bacteria who would then enrich the soil. A moment’s impatience affected years of poor yields and extra maintenance work.
It was my study of permaculture and its thoughtful design principles – which emphasize careful stewardship of all resources – that made me go ahead and bite the bullet. But I did one better than just changing the direction of the beds.
I ripped out the paths and beds, digging trenches on contour (perpendicular and level to the slope of the hill) and mounding up soil below in what is called a swale.
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from solutionsmapping.com . This diagram helped me tremendously when trying to understand how swales actually worked.
Permaculturists turn first to swales (and other major earthworks designed to slow, trap, and absorb water) when designing a garden. Though mine are really “mini swales” measured in feet instead of yards, the principle is the same.
The flattened perspective makes it hard to see, but those two darker swaths edged by white fabric are actually filled-in trenches. I dug about 8″ deep, which was all I could do with a shovel on this kind of soil, then lined the trough with recycled landscape fabric and backfilled with deep mulch. So the paths are level to walk on, but function as a sponge for all the water that ends up pooling underneath.
If we get a really tremendous rain and the pathways actually fill up, the excess of the highest one is designed to flow into the lower one, and so on, to direct the water where I want it. At least, that’s what will happen if I dug them right.
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It’d be such a beautiful slope, if only it faced South.
So swales are like little terraces except in an inverted S shape instead of flat across. I need to plant the lower sides with something good at holding soil, but smaller than comfrey – I was thinking alfalfa, or maybe strawberries. Last year they were so good! Any other ideas?
I got the middle bed thickly planted with onion sets & mulched. (Then I lay a length of wire fencing across the top of it. Otherwise the chickens would just get in there and kick it all up and I’d have to plant everything again. Nice that the 4′ width of the bed is such a standard size.) I have high hopes for them doing well; the beds should be high enough to be nicely oxygenated but also damp enough for plants to thrive.
When I get time, I’m planning on doing the other half of the slope – the one that points East – as well. But as it’s the main entrance, it’s tough to figure out how to plan it in the most efficient way. I don’t want to have to zig zag all the way down when I’m just heading to the chicken coop.