Keyline design
Keyline design is a landscaping technique aimed at maximizing the beneficial use of water resources on a plot and avoiding drying, erosion, and excess water phenomena.
A keyline is an inflection point perpendicular to the direction of water flow. The keyline is located where the slope begins to weaken and the water flow slows down. A keyline is first identified using a topographic survey (which can be produced on site using drones), then dug with a ripper, behind which a cover crop or perennial species can be sown.
The furrow captures water and distributes it uniformly across the entire valley (following contour lines), without disturbing either the soil or the general water flow.
Description and objectives
The keyline denotes a specific topographic feature related to the natural flow of water. Keyline design is a system of principles and techniques for landscape development to optimize the use of their resources: water, sunlight, exposure, wind, flora, and fauna. Each landscape (the agricultural space as a whole) has climatic and topographic particularities. Keyline design is to be applied to each farm or land in a personalized way. It is one of the elements at the base of permaculture design.
By taking into account all elements of a landscape, this approach contributes to the reconstruction and consolidation of ecosystems. Therefore, its application is not limited to arid zones and large plots. It can be used regardless of the climatic zone and the size of the land considered. It will allow both to direct, infiltrate, store, distribute runoff water and evacuate excess water, but also to infiltrate oxygen and nutrients, all with the aim of promoting the development of a living, deep soil with high biological fertility. It is less costly to achieve this goal in a landscape organized for this purpose.
If the soil is dry, when rain occurs, runoff water will be captured in the furrows and prevent erosion. Conversely, if the soil is already saturated with water, during rain, runoff water will also be directed into the furrows and can be evacuated into a retention area (basin, pond, swale).
Australian farmer and engineer P. A. Yeomans invented and developed keyline design in his books "The Keyline Plan", "The Challenge of Landscape", "Water For Every Farm", and "The City Forest".
Keyline design appeared at the advent of chemical agriculture and was shunned. In the current period of agricultural transition, permaculture, keyline design, holistic management, biodynamics, agroecology … are all tools available to help us best express the potential of each land, each terroir.
Advantages
- Better infiltration and distribution of water → limiting runoff and thus erosion risk.
- Management and regulation of excess water → replenishment of groundwater.
- Better air-water exchanges with plants, soil, and subsoil → better root penetration which, by decomposing, creates humus.
In summary: Keylines create a production zone that promotes rooting, maximizes water use, life, and rapid regeneration of the environment while avoiding damage caused by excesses (heat, drought, and/or floods).
Implementation
In nature, straight lines are almost nonexistent and perfectly flat soils are very rare. By taking into account all elements of a landscape, keyline design contributes to the reconstruction and consolidation of ecosystems. Water resource management of the landscape is to be designed after considering climate and topography (the shapes and slopes of the land).
The work of implementing keylines will be carried out using a ripper or a ripper (Yeomans) that works the soil without disturbing the horizons. For this, you will have to wait until the soil of the plot is well drained and not too dry. Then you must follow the contour lines and trace the keylines perpendicular to the slope.
This soil loosening leaves a pattern engraved on the soil that influences surface water movements. It is more than a hundred small furrows per hectare that trap water, allowing it to infiltrate. When the soil is saturated, water follows these furrows which act as small channels. By organizing the layout of these channels, one can influence the distribution of water on the land and lead water from hollows (called valleys in keyline language) where it tends to accumulate towards the ridges (called crests) which dry out. Yeomans passed on know-how on how to operate the ripper to achieve this effect, based on determining key points and key lines. These furrows are called keylines and the soil is said to be worked in keyline. These keylines also serve for gravity irrigation, by diffusing water both horizontally and vertically.
Over time these furrows risk filling up. To prevent this, the best way is to plant anchoring plants such as perennials (hedge, trees, vine, aromatic plants...) to continue having this effect of retention and distribution of water along contour lines.
Taking into account the "key points"
Contour lines are marked by lines of thalweg (hollows) and ridge lines (humps) that alternate along the relief, some lines being more pronounced than others. The most important contour line will be the one starting at a point located on one of the thalweg lines where runoff velocity is highest. This point where waters gather is called the "key point", it is from this point that ravines form because it is where the water current is strongest.
The contour line passing through this key point is called the "key line", literally "key" "line" in English, hence the name "keyline". It is from the key point that the first keyline is traced, the following ones will run parallel to this line as long as the topography remains homogeneous.
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Keylines will be traced with one or more teeth, as deep as possible: 60 to 80cm, every 0.75m to 1.50m in width (in vineyards), depending on the slope and equipment used.
Be careful, the keyline must not continue along the entire contour line. It must start from the key point (where the water flow descends into the valley) and follow the contour line on both sides of the valley up to each crest. Indeed, the keyline must stop to allow water to enter the soil and prevent it from evacuating into the next valley.
Swales
Swales (or baissières) also follow contour lines, they are closed ditches. One should try to position swales starting from the "key point" of the first keyline. The swale will become a super keyline that will accumulate much more water. It will be downstream of the slope, topped by a small mound increasing water storage capacity. Various forest species and fruit trees, small fruits, and perennial vegetable crops will be planted on this mound. This swale will also distribute, infiltrate, and store runoff water. Each swale will be equipped, at one end, with an "overflow" that will evacuate excess water to different ditches which can feed one or more ponds.
Warning: swales are massive hydrological elements that change the landscape topography. It is essential not to implement such a system before having implemented all other agroecological solutions (cover crops, organic matter input, possible keylines). In most cases, swales can become problematic if not well managed, especially in winter with excess water. Moreover, it is important to validate the geological aspect of the soil (with a hydrogeologist) to ensure that the system implemented does not do more harm than good... Generally, such a system will only find its place in regions with a Mediterranean climate!
Further reading
- Permalab
- Keyline Design (paysages-fertiles.fr)
- Optimal conditions for ripping - Fabian Féraux.
- What is Keyline Design? or how to increase natural soil fertility? - Permaterra.
- The Water Revolution in India #1: Solving the crisis in 45 days with the Paani Foundation - Andrew Millison.
- Harmonizing agroecological approaches in viticulture - Ver de terre production.
- Before Permaculture: Keyline Planning and Cultivation (permaculturenews.org)
- YouTube channels of Richard Perkins and especially his book "Regenerative Agriculture" (in English)
Sources
- Malard Alain. Vines, wines and permaculture. Editions France Agricole. 2021.
- Wikipedia page on Keyline design
- Keyline design, a tool for regenerative agriculture - Possible media
- "Introduction to Keyline Design" with Simon Ricard:
