Keyline Design

Keyline design begins with a survey, not a tool. You find the keypoint — the place on a slope where the land shifts from convex to concave — and you draw a line from it that follows the contour but is not itself a contour. That line, the keyline, is the reference for everything else: where the swales go, where the trees go, where the water is allowed to collect.

The point is not to stop water. It is to slow it, spread it, and let it sink where it falls, rather than collecting it into a channel that carries it off the property taking topsoil with it.

Two swales on the south slope, cut on a slight downhill grade toward a vegetated sill, and a third on the north side that feeds the wet corner. The spoil from each was used to build the berm on its downhill edge, planted with clover and comfrey. Neither swale is deeper than a spade. Neither is meant to be a ditch.

We surveyed with a laser level and a great deal of string. The plan was drawn at a scale of one inch to twenty feet and revised three times after walking the ground in the rain, which is the only way to see what water actually does here.

In a normal November, the south slope used to sheet water into the ditch within an hour of heavy rain. It now takes most of a day to reach it, and it arrives clearer. That is the whole measure: slower, cleaner, later.

The swales are the cheapest infrastructure on the property and the most likely to outlast us. They require weeding, not maintenance.