Hugelkultur swales, or DIY terracing on a muddy slope
Our property is a long, narrow, wooded strip that slopes gently from a ridge to a creek. At least, that’s what its mirror image on the west side of the creek looks like. On our side, two large, flat, cleared areas interrupt the descent. One is the site of the old gravel mine, near the creek, and the other, closer to the ridge, is the house site. The state Department of Environmental Conservation “restored” the gravel mine some years ago, and now it’s a brushy meadow. Later, in 2009, we built a house near the top of the hill. The east side and part of the south side of the house are built into the hill and buried in mud. This is good for keeping the house cool in the summer. But there’s still a bare, steep, muddy slope above the house and another, steeper muddy slope above the meadow.
Neither of these slopes is an urgent problem. We’ve seeded them both with rye and clover to slow the erosion, and weeds are spreading there as well. The slope above the house drains into a ditch behind the house, which meets up with some other drainage ditches and empties into a pond below the house. (At least we call it a pond; it was dug about a year ago but has yet to fill up for more than a few hours at a time. Except after a heavy rain, it’s a deep crater with a puddle at the bottom.) The lower slope has no drainage, but whatever washes down it goes into the meadow, which may benefit from some extra dirt. Parts of the meadow are still quite gravelly.
But the Hudson Valley is rainy and is particularly prone to what are called “large rain events.” Sometimes, as much as six or seven inches of rain falls in as little as an hour or two, according to our official rain gauge, a ruler in a five-gallon bucket. So, drainage ditch or no drainage ditch, nutrients wash out of the soil, make their way down into the creek and eventually flow into the ocean, where they produce “dead zones.” Considering that the muddy slopes are mostly clay already, we don’t want to lose any more nutrients. Here, as in the rest of the world, topsoil is vanishing at an alarming rate and must be made up with chemical fertilizer derived from petroleum – in no way a sustainable solution.
Hazelnuts in the Mud
Ultimately, we need trees on these bare slopes – trees that will hold the water with their roots. Right above the house, in particular, we need fruit and nut trees that won’t grow large enough to damage the house if the wind blows them down. (North-facing slopes, which we have, are actually good for flowering trees, though not for much else.)
I’m thinking a row or two of hazelnuts would be just right above the house. They are small enough not to fall on us and will produce a delicious, edible crop conveniently close by. Hazelnuts were once an important part of this ecosystem – and they still grow wild in our county, according to the USDA plant database – but I have never seen any around here. (Which doesn’t mean they aren’t here, even on this property. Completing the census of what’s growing here is one of my projects for this coming year.)
But how can we plant hazelnuts on a muddy hill? What will keep them from washing away, and what nutrients will feed them?
In many cultures, slopes are terraced for planting – which is, frankly, a lot of work. Similar approaches promoted by permaculturists involve digging swales, or ditches, along the contour lines, or plowing into the subsoil at a slight angle from the contour lines using what’s called a “keyline plow.” Those methods also require a lot of work as well as heavy earth-moving equipment.
DIY Terracing
What I’m trying – based on Jerome Osentowski‘s ideas, as reported in the wonderful permaculture book Gaia’s Garden – is a do-it-yourself terracing/swaling method. Instead of digging holes in the mud, I’m building up berms along the contour lines with rows of rotting logs. The logs should act like sponges, catching and slowing the water as it runs down the slope and giving it more time to sink into the earth. (If this works, that pond will never fill up.)
In addition, as the logs rot, they return organic matter to the soil, providing nutrients for the hazelnut trees or whatever we eventually plant there. Rotting logs actually make a great base for raised garden beds (this method is called hugelkultur, which you can pronounce in either the German or the English way); following the hugelkultur method, I can pile leaves, compost or rabbit manure on top of the berms before planting trees on them.
Fortunately, we still have plenty of wood from the trees that we cut down to build the house. (The house is concrete; we didn’t use the wood for building.) Some we gave away to people with wood-burning stoves, but the rest has been sitting in piles behind the toolshed for several years, not doing anything particularly helpful. On nice days, when I have a spare hour, I carry logs from the pile and build them into berms. It’s cheaper and more fun than going to the gym. And maybe, in a few years, it will turn the muddy slope into a lush garden.
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