Keyline design

Keyline design is a technique for maximizing beneficial use of water resources of a piece of land. The Keyline refers to a specific topographic feature linked to water flow. Beyond that however, Keyline can be seen as a collection of design principles, techniques and systems for development of rural and urban landscapes.

Keyline design was developed in Australia by farmer and engineer P. A. Yeomans, and described and explained in his books The Keyline Plan, The Challenge of Landscape, Water For Every Farm, and The City Forest.

P. A. Yeomans published the first book on Keyline in 1954. Yeomans described a system of amplified contour ripping to control rainfall runoff and enable fast flood irrigation of undulating land without the need for terracing.

Keyline designs include irrigation dams equipped with through-the-wall lockpipe systems to gravity feed irrigation, stock water, and yard water. Graded earth channels may be interlinked to broaden the catchment areas of high dams, conserve the height of water, and transfer rainfall runoff into the most efficient high dam sites. Roads follow both ridge lines and water channels to provide easier movement across the land.

The backbone of Yeomans' keyline design system, the outcome of fifteen years of adaptive experimentation, is Yeomans' Keyline Scale of Permanence (KSOP), which identifies typical farms' elements ordered according to their degree of permanence:

Keyline considers these elements when planning the placement of water storage, roads, trees, buildings and fences. On undulating land, a keyline approach involves identifying several features namely ridges and valleys and the natural water courses seeking optimum water storage sites and potential interconnecting channels.

The water lines identified from the land-form subsequently provide optimal locations for the various less permanent elements (roads, fences, trees, and buildings) to optimize the natural potential of the landscape.

In a smooth grassy valley, a location called the keypoint can be found where the lower and flatter portion of a primary valley floor suddenly steepens. The keyline of this primary valley is revealed by pegging a contour line through the keypoint, within the valley shape. All the points on the line are at the same elevation as the keypoint. Contour plowing parallel to the Keyline, both above and below will automatically become "off-contour" but the developing pattern will tend to drift rainwater runoff away from the valley centre and incidentally, prevent erosion.

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