Permaculture Designers Manual
CHAPTER 9 –
EARTH WORKING AND EARTH RESOURCES IN PERMACULTURE
Section 9.7 –
Earth Constructs in Permaculture
Where, earth is dug, banks are raised. There is a great concentration on the holes, and far less on the mounds, so that “spoil” in mining becomes a pollutant.
This need not be the case, providing topsoil is first removed and then returned to cover the spoil, in stages or as a whole job.
Just as we can hollow out land, we can also raise roads and banks above marsh or flood levels to deflect winds, noise or water.
Banks raised by machines can serve the following purposes:
1. Shelter for houses and fields;
2. Plant sites for windbreaks (on the crown of the bank and in its lee);
3. Walls of houses or storage barns;
4. Containments for large inflammable fluids, and fireproofing;
5. Noise deflectors and absorbers, e.g. at airports and along highways;
6. Tracks and plant sites in marshes and on day soils subject to flooding;
7. Patterns to deflect and direct wind and water to storages or energy systems;
8. Flood or tide control systems (polders and levees);
9. Railways and road grade adjustment;
10. Earth ramps and stands; and
11. Earth walls or “ha ha” fences.
These are further elaborated below:
1. SHELTER FOR HOUSES AND FIELDS
Either in flatlands or on high exposed sites, an earth crescent bowed into the cold winds is the fastest way to create shelter and warmth on its lee side.
Even a few blade side casts run along a field boundary provides cover for hedgerow and windbreak species and may act as a swale for root water collection.
High banks of 2.5m (9-12 feet) close behind house sites, whether excavated or raised, create instant shelter over the occupied site, shelter which may be further reinforced with trees. (Figure 9.16)
This is a long term and considerable heat energy saving in cold climates and a shading or cooling wind director in warm climates.
Figure 9.17 shows an actual ground design for a flatland site with cold southwest, hot northwest and cooling northeast winds, all controlled by one earth bank and the pond formed by the excavation.
2. PLANT SITES FOR WINDBREAKS
Low side casts heap up topsoil, create shelter and catch or delay
run-off, as well as, reduce root competition for a year or two, all good reasons to side cast for long windbreak sequences, and in wetter ground to establish willows, poplars, and tamarisk above water-logged ground. (Figure 9.18)
3. HOUSE OR BARN WALLS
Unrealized by most architects and home builders, machines exist which can raise and compact a complete house or barn wall in a morning’s work.
All we need to add is floor and roof (another two days work) to be in a long-term, fireproof, silent, energy-conserving and sheltered house.
This technique is suited to open-space situations, cheap barns and large outbuildings.
As the walls are raised, a smaller tractor and roller can compact them. Almost any earth will do, providing the compacted rest angle is watched.
This technique is not suited to sands unless wall corners are bagged (stabilized with soaked bags filled with cement and sand or sandy soil). Figure 9.19
Whether for inflammable fluids or as fire-proofing and especially effective against radiant heat, earth walls can surround tanks.
Above-ground wildfire radiation refuges in bush land are earth-covered and may be built off forested roads and near isolated bush houses.
5. NOISE DEFLECTORS OR ABSORBERS
Traffic noises are effectively blocked from housing by earth walls and plants on these banks decrease noxious fume effects. Deflection of noise is effective for long wavelength noise only.
6. TRACKS AND PLANT SITES IN MARSHES
Earth banks, islands, and mounds in marshes give multiple opportunities to access and place trees and structures. Mounds in ponds isolate useful but rampageous species such as thorny blackberries and runner bamboo, while banks allow foot or vehicle access across and into marshes to place and service duck nest boxes, to harvest fruit and vine, and to attend to fish ponds. (Figure 9.20)
The raising of a bank in marsh is an interesting operation; the best tool is a very light “swamp” tractor with wide tires or tracks and a swivel bucket (an excavator).
This unit, perhaps using “mats” in very soft or silty ground, can dig and raise an earth bank where the ground is too soft for the operator to walk. Equipment can be tight for the first crossing, the aim being mostly to throw up a broad earth mound to dry out, so that a safe transit of heavier equipment can be made at a later date and a substantial bank raised for a road bed or planting.
It is easier, of course and less harmful, to first raise banks and then create a marsh by building a low berm. Natural marshes need protection for their unique values and for waterfowl.
“Mats” are three bulky wooden gratings, made of 10cm by 15cm (4 inch x 6 inch) timbers, which the bucket machine stands on. At each move the machine itself recovers one from behind and places it ahead.
Once the first mound is built, larger excavator machines can reach out to dig deep channels and build high banks of great solidity or the smaller mound can be leveled by a light tractor for foot traffic.
Draglines are not really an alternative in mound building and in timbered swamps they are impractical.
7. WIND AND WATER DEFLECTION
Figure 9.21 illustrates a design based on older Afghan mills of a saddle or ridge wind tunnel for mill power. Systems for water diversion are discussed in Module 11.
8. FLOOD AND TIDE CONTROL (polders and levees)
Well maintained earth banks are the only protection of houses and villages in flood plains and below tide level. They are, in effect, reverse dams, the inhabitants living inside and the waters contained outside.
Mounds can be built as flood refuge islands in many deltaic areas, containing storage barns and refuges in fields subject to periodic flooding, dangerous to people or animals.
Causeways of earth are often used to access low mounds or islands near shore. Bangladesh and other deltaic areas need wooded refuge mounds just for the survival of people.
Such mounds can also be made in fire-prone sites, where villages and houses are safe in lakes or on moated islands. Peninsulas should be included in dam construction for this purpose by designers. (Figure 9.22)
9. RAIL, CANAL, AND ROAD GRADES
These common banks and cuttings are all well-known to all of us.
10. EARTH RAMPS AND STANDS
Earth ramps and stands are of great use for at least these reasons:
To unload trucks from the side or back (heavy objects and wheeled vehicles);
To load cattle to trucks, at various levels;
To unload hay or bales into the upper floors of a barn for use at lower levels; and
To load and unload boats into water.
Once built, they are permanent in use and sometimes a whole district can use the facilities of one loading unloading ramp. The loading face itself must be stabilized with stone, concrete, or beams. (Figure 9.23)
11. EARTH WALLS OR “HA HA” FENCES
The “ha ha” is a below-grade ditch, which acts as a fence. It is used In classical vista gardens where views are to be uninterrupted and in zoos for direct viewing of large and potentially dangerous animals.
It is also a defense for villagers against stock where the resources do not allow wire fences, but labor or a machine can be obtained.
It is essentially a deep pit, dry or wet, with one steep wall faced by stone (Figure 9.24). It can be scaled to size for the species excluded.
The same machines that build roads will also build wetlands, swales, and small dams suited to wildfire control and wildlife.
Underpasses and guide fences allow migrating wildlife to cross road and rail ways without accidents.
Roadsides can be an area for the preservation of bunchgrasses, sagebrushes, rangeland and meadow plants, and remnant forests along their way, with pull-over areas and vegetation maps, geological features and archaeological or fossil remains clearly indicated. Such planning must precede actual construction.
We pour kilometers of black bitumen surface, but fail to lay under it pipes for heat pumps that would heat the towns through which the road passes, and we fail to harvest and store road run off for local irrigation and wetlands.
All this will change only when well intentioned people govern the spending of public monies, or when road engineers are trained in Permaculture and look upon roads as a community resource!