Swale (landform)

A swale is a shady spot, or a sunken or marshy place; in United States usage in particular it is a shallow channel with gently sloping sides. A swale may be natural or human-made. Artificial swales are often infiltration basins, designed to manage water runoff, filter pollutants and increase the soaking of rainwater into the ground, and a bioswale is a swale built with plants or vegetation included on purpose. The permaculture movement, associated with Bill Mollison, David Holmgren and other advocates, popularised swales as a rainwater-harvesting and soil-conservation strategy. In that setting a swale is usually a water-harvesting ditch dug on the contour, also called a contour bund, which slows runoff and spreads it horizontally across the landscape.