Slow, spread, sink
Every water earthwork serves one goal. Interrupt runoff. Convert surface flow into soil moisture and groundwater.
Rain on an unmanaged slope leaves the site in minutes. It accelerates downhill, strips topsoil, and the subsoil stays dry. Earthworks reverse the pattern by holding water long enough to soak down.
P.A. Yeomans articulated this clearly in his Keyline Design system, developed in Australia in the 1950s. Water concentrates in valleys and starves ridges, so his plow pattern moves water back across the slope. Geoff Lawton and Bill Mollison extended the toolkit into swales, berms, terraces, and diversion drains at every scale.
The payoff is dramatic. A property shedding 80 to 90 percent of rainfall can be rebuilt to infiltrate 80 to 90 percent instead. Water tables rise, soil stays moist between rains, and irrigation needs drop or vanish. Erosion stops. Deep-rooted perennials become possible on ground that would have failed them.
Read the contours
Every design starts with the shape of the land. Contour lines connect points of equal elevation and show you where water moves and where it pools.
On a topographic map, close lines mean steep ground and fast water. Wide lines mean gentle ground and easy infiltration. Valleys show as V-shapes pointing uphill. Ridges show as V-shapes pointing downhill. Saddles and benches mark possible pond sites.
A-frame level. Two legs of equal length, joined at the apex, with a plumb bob hanging down. One person can walk a true contour across any slope. Slow, accurate, almost free.
Bunyip level. A long clear hose filled with water. Two people read the ends. When the water lines up, you are at the same elevation.
Laser or optical level. A rotating laser and receiver rod can shoot 100 metres of contour points in minutes. For anything above 2 hectares, hire a surveyor or fly a drone. Photogrammetry now delivers centimetre-accurate elevation models in a single flight.
The main structures
Water earthworks run on a spectrum from passive infiltration to active redirection.
Swales on contour. Level ditches dug along a contour, with the spoil mounded downhill as a berm. They catch runoff and hold it until it soaks in. Default choice on moderate slopes. Usually the first earthwork on a site.
Berms and bunds. Raised earth mounds with no trench. A berm uphill of a garden diverts sheet flow around it. A crescent bund around a tree concentrates runoff at the root zone. Quick by hand, precise in effect.
Terraces. Flat shelves cut into a hillside, held by a wall of stone, earth, or timber. They permanently convert steep slope into level growing surfaces. Right choice on steep terrain where swales cannot hold enough. Long history from the Andes to Southeast Asia.
Diversion drains. These have deliberate grade. They move water from one place to another: protecting structures, feeding a pond, or routing overflow between swale systems.
Plant as you dig
Earthworks without planting are temporary. Bare earth erodes. Berms slump. Trenches silt up. Vegetation goes in the moment construction ends.
Pioneer species and nitrogen-fixing trees come first on berms and terraces. Deep roots stabilise the earth. Leaf litter builds topsoil. Nitrogen fixation feeds later plantings. Black locust, tagasaste, and native acacias tolerate the drought-and-flood cycle of new earthworks.
Mulch swale trenches heavily with wood chips or straw. Slows flow, blocks weeds, builds organic matter. Some designers plant the trench floor with comfrey or chicory, which tolerate inundation and pull minerals up from the subsoil.
The berm is where production lives. Food forest design maps straight onto it. Canopy trees on the crest. Understory on the slopes. Ground covers down the faces. The infiltrated water creates a moisture lens that tree roots reach in dry months. Sites in southeastern Australia, the Middle East, and East Africa run productive food forests on 250 millimetres of annual rainfall with no irrigation beyond what the earthworks capture.
Hand tools or machinery
The call depends on scale, soil, and budget.
Under half a hectare, hand tools work fine. Mattock, shovel, wheelbarrow. A motivated person moves about 1 cubic metre per hour in reasonable soil. A 50-metre swale, half a metre deep and a metre wide, is roughly 25 cubic metres. Three to four days of solid work for one person. Costs nothing but labour, and the constant fine-tuning produces excellent earthworks.
Above half a hectare, or in heavy clay and rock, bring machinery. A 3 to 5 tonne excavator is the standard. It finishes in a day what a hand crew would spend weeks on.
One warning. Most operators dig drainage ditches with grade and will instinctively add fall to a trench. Walk the marked contour with them before they start. Check levels often.
For keyline plowing and broad-acre contouring, a tractor with a Yeomans plow or deep-ripping subsoiler covers ground fast and cheap. Not earthmoving, but deep cultivation along contours that opens infiltration paths in the subsoil. A weekend with a rented excavator builds a swale system that harvests water and supports plantings for the life of the property.
See also
- Swales on Contour: detailed build guidance for the most common structure
- Keyline Design: whole-landscape water distribution by contour plowing
- Check Dams: small barriers that stabilise gullies and trap sediment
- Reforestation Techniques: planting strategies for revegetating earthwork sites
- Food Forest Design: multi-layered plantings for swale berms