One of my early projects in the forest garden was to build mounds and swales in an attempt to deal with waterlogged soil.  The mounds did their job well --- they raised plants up high enough out of the water that they survived.  The swales were more problematic.

The permaculture literature discusses swales as used in dry climates.  There, swales capture runoff so the precious liquid doesn't disappear onto the neighbor's property.  A dry climate swale is basically a linear, wet-weather pond that runs along a contour line, filling up during rains, then releasing the water into the surrounding area over the days and weeks that follow.  Bill Mollison and other permaculture practitioners plant moisture-loving trees and shrubs on the downhill side of these swales for free irrigation.

In wet climates, a different kind of swale is used to channel runoff across flood-tolerant vegetation, cleaning the water and preventing erosion.  In this case, swales are built perpendicular to a slope to keep water moving, then check-dams are added at intervals to slow the water down and help silt drop out.  Wet climate swales are often located next to roads or parking lots, as is shown in this photo, and they allow runoff to sink into non-waterlogged soil.

You'll notice that both types of swales capture water and let it sink into the ground.  The big difference in function is that dry climate swales can be built in ground that doesn't "perk" since the goal is to make the water stick around as long as possible.  Wet climate swales are built on well-drained soil with the goal of getting that runoff into the groundwater as quickly as possible.

I wish I'd realized the difference between dry climate and wet climate water management when I installed my swales, because I learned the hard way that creating a dry climate swale in our neck of the woods can turn wet ground into a marsh.  Marshes have their place, but a marshy ditch in the middle of a "lawn" becomes a mowing hazard quickly.  Rather than ruin the lawn mower, Mark skipped mowing these spots, with predictable results.

As part of my campaign to streamline maintenance of the forest garden, I'm starting to build the swales back up to ground level.  I figure rotten logs in the holes will capture and hold water, releasing it to the nearby plants during dry spells.  Once I hunt down enough logs to fill the swales up, I'll mulch over top so that that area won't need to be mowed at all this year.

Of course, even my improved swales hold onto water rather than draining it out of the waterlogged area.  I might eventually turn to ditching to deal with that issue, but for now, I think I can take advantage of the extra water.  I'll just keep building up so that roots don't drown.

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About us: Anna Hess and Mark Hamilton spent over a decade living self-sufficiently in the mountains of Virginia before moving north to start over from scratch in the foothills of Ohio. They've experimented with permaculture, no-till gardening, trailersteading, home-based microbusinesses and much more, writing about their adventures in both blogs and books.



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