Continuing my notes on the book Introduction to Permaculture (1991/2009) by Bill Mollison, here is Chapter Two: Broadscale Site Design. (Intro and Chapter One) I am relying mainly on my sketchy notes here, without a book in hand to check quotes, accuracy, etc. (there is a version of the book online, with lots of illustrations by Reny Mia Slay). Any misrepresentations of Mollison’s words or work are mine alone and completely unintentional.
CHAPTER TWO: Broadscale Site Design
2.1 The design is the most important thing
Set goals, then look at your site with the goals in mind. Or, look at the site and let the goals suggest themselves: “What does this land have to give me?” It’s always easier to see the site with goals in mind, though the goals may later turn out to have been unrealistic. Design is a continuous process.
2.2 Identifying Resources
Observation and research.
Maps. Note area species, rainfall. Ask others about garden pests.
Feature map: waterways, vegetation, soils, geology, access, contour lines, improvements. Never try to design a site just by looking at a map; a map doesn’t represent the complex reality of nature; the map is not the territory.
Observe: Notebook, photos, sketches. Note good views, soil colour/texture, patterns, processes, water flow, wind damage, sun and shadows. Look for landscape indicators — vegetation tells us about soil fertility, moisture, microclimate. For example, rushes mean the soil is boggy; dandelions tell us the soil is acidic; trees with most of their limbs on one side might show direction of strong prevailing winds.
Watch what plants do to survive and imitate them.
(Below, illustration of sun/shadow from Mollison’s book, at Scribd.)
2.3 Land Form (Topography)
Topography affects microclimate, water drainage, soil depth, character of the site.
Note sun- and shade-facing slopes; cliffs and outcroppings; drainage; views; boggy areas, eroded areas.
Permaculture can be developed on any site. It’s not necessary to try to change a stable landscape.
Make diagrams of summer and winter sun zeniths and angles. [Suncalc.net can show you this for your site if you enter the address
2.4 Climate and Microclimate
Factors affecting microclimate include:
Topography – hilly and flat areas
Aspect: how slopes are oriented to the sun. Use sunny slopes for fruits and marginal plants. Note absolute height of sun in sky in summer and winter, and note the distance it travels on its path. Steepness of slope also matters.
Cold air drainage: Cold air sinks – use vegetation to divert it, or it can be dammed. More chance of frost on hilltops and in valleys; usually the least frost is on the upper- and mid-slope, above 21 yards high. Cold air flows like treacle, not like water, i.e., it moves slowly around objects and obstacles.
Winds: Wind speeds increase going uphill and decrease going downhill. Also increases going past a constriction (Venturi effect).
Elevation: Every 100 meters (330 ft) of altitude = 1 degree of latitude, so at 1,000 meters (3,300 feet) temperatures are equal to the climate 10 degrees higher in latitude. [My elevation is 1,290 feet.]
Water Masses: Can use reflected sunlight from water to moderate temperatures and give extra warmth and light to marginal plants.
Structures: Trellises, berms, greenhouses, fences, walls, etc., affect microclimate by modifying wind speed or temperatures.
Soils: Soil has a small influence in the amount of heat it conducts and the light it reflects, and because of differing water and air content. Remove mulch in spring so ground can warm up. Mulch is an important aid in water retention.
Vegetation: Vegetation has a profound effect on climate, modifying the temperature on the site by transpiration, convective transfer of heat, shading, wind protection, insulation.
- Transpiration — “sweating.” As temperatures drop, humidity increases because water from plant leaves turns into water vapour.
- Convective transfer of heat – Plants absorb sun energy. Large amounts of heat can be absorbed into the leaf canopy, and as the surrounding air is heated, it rises, leaving cooler air lower in the forest. At night, the process reverses.
- Shade – Powerful effect of blocked sun. Trees with dense foliage can filter 75-90% of the sun’s energy. Shiny leaves (like poplars) reflect sun. Sun traps are parabolic arcs to let wind go around.
- Windbreaks – Soil can be 10 degrees warmer in a sheltered area. Dense windbreaks give protection to a distance of 2-5x their height. Permeable windbreaks give less protection overall, but protection continues farther out, to a distance of 25-30x the height. Also consider other features of functions of the tree, such as nuts, nitrogen fixing, honey, erosion control.
- Insulation – Bushes and vines bear a building; shrubs provide a ‘moisture envelope’ around a tree. Snow. Ground covers and mulches.
In permaculture, soils are not considered a severe limiting factor as they can be improved over time.
Don’t turn the soil. Plant trees and shrubs to protect the soil. Encourage worms to aerate (mulch or compost).
To rehab soil:
- Prevent erosion.
- Add organic matter.
- Loosen compacted earth, aerate.
- Modify pH or grow plants suitable to it. For acid, use lime, dolomite, chalk, gypsum to raise pH. For alkaline, use phosphate.
- Correct nutrient deficiencies with organic minerals and manures.
- Encourage biological activity.
Two kinds of mulch: dead (dried out – leaves, straw, cut vegetation) and living (growing under plants).
Cover crops. Green manures. Chisel ploughing.
Fixed: Rainfall and other precipitation. Changeable: Drainage, plant requirements, soil cover (mulch).
Swales: Hold water in soil and let it seep out over hours or days. Can be made with small ridges, rock piles, hollows. Trees must accompanying swaling. Follow contour of land. Space between swales: 3 to 10x swale width. If swale base is 2 meters, then interswale space is 6 to 20 meters. Swales can take years to become efficient.
Tanks and Dams: For collecting roof run-off. Water outlet pipe should be at least 6 cm from bottom of tank so built-up algae is not disturbed.
2.7 Siting Important Infrastructure
Access roads: for materials to be brought in. Always finish driveway up-grade to the house to allow for proper drainage. Roads should run along contours, with no steepness and with good drainage. Roads should also, if possible, fulfill other functions (dam walls, fire-breaks).
Siting house: Off main highway but closer to main road (that’s not a highway) is best. Look at sun aspect when siting. Don’t build on a slope greater than 14 degrees or more than 2-3 degrees below grade (drainage issues). This amused me: “Although most of us put ‘view’ as a priority, it can lead to siting a house inappropriately, usually on a hilltop where access is difficult and winds are frequent. So we may have to sacrifice the view from the house and instead build a little retreat up on the hill, with comfortable chairs.” Don’t build on top of an exposed hill or ridge. Don’t build in a forest. Don’t build on riverflats or gullies, steep land, near volcanoes!, near rising sea levels, “or in fact anywhere inevitable disaster threatens.”
Fencing: Total control of small animals should be confined to zone 1 only, with a small-mesh sturdy fence. Instead of a fence in other zones, an unpalatable hedge species might work. A fence can also be used as a trellis.
In the first 2-6 years, you may need so many plants that a small plant nursery should be established to supply the 4,000-10,000 plants needed on a hectare (2.4 acres). (??)
When designing, reserve space for energy systems (wind, tide, solar, water).
Implementation order: 1. Structures and designs that generate energy. Then, 2. Structures and designs that save energy. Then, 3. Structures and designs that use energy.
What’s worth main-cropping? Crops that need little attention after established — potatoes, corn, pumpkin, hardy fruits, vines. Crops that are easy to harvest, store, and use. Crops that can form dietary staples (potatoes, cassava, taro, pumpkin, nuts, corn, high energy-value foods).
2.8 Design for Catastrophe
Includes discussion of designing for fire, earthquakes, floods, hurricanes. Some fire-resistant plants: figs, willows, mulberries, some acacias, passion fruit, ivy, comfrey, taro, various succulents, wormwood, aloe and agave species, iceplant, sweet potato, wandering Jew, sunflowers, pumpkins. This advice seemed not all that useful for those of us in New England: “During an earthquake, escape into a clump of bamboo.”
Next up, Chapter Three: Pattern Understanding.
(* Featured photo is my fruit guild, on a slope, in June 2012, when I was just laying it out and trying to make a little swale or water dam from rocks. It didn’t work.)