Transcript of Keyline Design. What is Keyline? Design strategy for passive rainwater harvesting and use developed...
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- Keyline Design
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- What is Keyline? Design strategy for passive rainwater
harvesting and use developed in 1950s in Australia by P.A. Yeomans
Influenced development of Permaculture and is highly compatible and
integrated with Permaculture methodology For the broadscale
landscape level, but principles work down to any small scale
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- Understanding Contour (Maps) Level: flat lines at right angle
to slope, curving as slope changes, around valleys and ridges.
Where water will not flow water flows at 90 degrees to contour.
Same height apart (intervals) Surface distance apart changes
depending on slope Each given a height above datum usually sea
level, but can be any other fixed point. Valley floor
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- Contour in a landscape
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- Creating a new landscape pattern for water flow Make/
facilitate/ allow water to do its duties: Passive (gravity powered)
and Positive impact Patterns to details: putting it all together in
an integrated strategy Plan the slowest longest route for water
through your system Always give water a way out/ onward (or it will
find its own!) = water moved by gravity
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- What do we need to do with rainwater? SSS: Slow it! Spread it!
Sink it! WHY?
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- High runoff and erosion Uneven distribution (space and time):
Boggy areas + dry areas, floods + droughts High evaporation, low
infiltration and low recharge of groundwater (wells and spring s
dry up) No SSS
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- Low runoff, soil conservation and soil creation More even
distribution: Even hydration of landscape and plant growth possible
throughout more of year Low evaporation,, high infiltration and
groundwater recharge (new springs form) With SSS HOW?
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- Keypoint and Keyline (plan view) The Keypoint marks a change in
relationship between the valley and its adjacent ridges
(shoulders). Keypoint is usually around where contour lines in a
valley first start to become further apart (can be slightly above
or below). Keyline is a level (or slightly sloping) line taken
around all slopes from the keypoint Valley floor Below keyline,
valley is wider and less steep than its shoulders Above keyline,
the valley is narrower and steeper than its shoulders
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- Keypoint (side view) Usually on or just below point where slope
turns from convex to concave Water runs faster so material is
eroded Water runs slower so material is deposited Convex erosional
slope Concave depositional slope Earthworks are much easier on
concave slopes!
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- Earthworks on slopes Aim to harvest as much water as we can,
while moving as little earth as we can. Convex/ erosional slope
Concave/ depositional slope To harvest the same amount of water, on
concave slopes we need to move less earth. The keypoint and the
keyline is the highest point in the landscape where we can easily
make dams Dam walls less stable Dam walls more stable
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- Some landscapes are not obviously concave or convex Break point
= where slope goes from shallow to steep and erosion begins
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- Ridges and Valleys Keyline Ridges Valleys Slopes are convex and
concave vertically AND horizontally: we call these ridges and
valleys. There are usually several within a single rainwater
catchment area, or watershed. Therefore keypoint valley dams are in
the highest, most concave slopes we can find. Why do we want them
as high up as possible?
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- Watershed = a distinct rainwater catchment area Main ridges
divide separate watersheds Primary ridges and valleys divide the
watershed Each valley keypoint has its own keyline Usually we start
from the valley with the highest keypoint or the biggest catchment
Which one is that?
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- Keyline Earthworks 1: Channels Keyline swales Catch surface
runoff water and fill up, soaking it in and evenly spreading it
out. Prevent runoff concentrating in the valleys. Can also overflow
into and fill dams. Keyline Diversion Drains Off-contour swales
leading slightly downhill. Can be away from keypoint, to direct
water out of valleys and towards ridges to rehydrate ridges or
towards keypoint dams.
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- Swales on-contour
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- Off-contour Swale
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- aka diversion drains
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- Keyline Cultivation Rip-plowing slightly off-contour downhill
away from keypoint to rehydrate ridges, which are then easier to
replant. NOT inversion plowing Only done once, or with a second
plow after a few years not regular plowing. Like hundreds or
thousands of very small absorbent swales, preventing rainfall from
concentrating in the valley. Water and organic matter fall into the
rips and is absorbed into the soil. Keyline Earthworks 2:
Plowing
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- Keyline plowing Helps to decompact soil and break hardpans
Allows water, organic matter and roots to enter deeper into the
subsoil Brings life into lower soil areas, turning it into living
topsoil Increases soil water retention capacity and self-fertility
of soil (from beneficial microbes)
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- Keyline plowing pattern First step of reconditioning slopes Can
be followed by reforestation or controlled grazing (high herd
density, short time)
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- Keyline Earthworks 3: Dams Keypoint Dam Where possible and
practical, dams are constructed on the Keyline in valleys,
connected by a gently falling diversion swales/ drains to carry
water to the dams and send overflow on to the next one. If used in
a series, no spillway is built, and the overflow goes down the
swale and into the next dam. Irrigation swale below dam
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- Can also just use a siphon
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- Keyline Irrigation
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- New pasture being irrigated by gravity pressure on "Nevallan
farm. Guideline timber strip forms a permanent marker for Keyline
cultivation. The truck in the centre background is travelling along
our Keyline road. The construction of a Keyline dam will often cost
considerably less than a pump and engine installed for spray
irrigation. The Keyline dam, its pipe and valve outlet, will
operate the same sprays with no pumping cost.
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- The Keyline often determines our land use on slopes
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- Other Dams We can build dams on any site given enough material
resources, but we should be careful to get best output for our
input and consider: Earth type Slope steepness Downstream safety of
houses and structures Height above use points Available catchment
or diversions
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- Saddle Dam Usually the highest available decent sites in the
landscape Can be fully excavated below ground or walled in from
either side. Can have horns or extensions at either end, and
connect to diversion swales/ drains.
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- Ridgepoint dam Another way to get water higher up in the
landscape (than keypoint). More effort for less water, but that
water might be VERY useful depends on your design context.
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- Contour Dam For the gentler, lower slopes
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- Flatland dams or Earth Tanks
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- Other Things to Remember Roads Design to catch their water and
use to fill dams Houses Never under dams! Forestry, Agroforestry,
Agricultural systems crops and animals. It is usually convenient
and good practice from most other viewpoints, to locate the
homestead and all farm buildings and their attendant roads in the
higher country. From the point of view of full Keyline development,
it becomes a part of planning to do so, in order to secure abundant
run-off water to fill the Keyline dams from these sources.
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- Which order to work in?
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- Keyline Scale of Permanence Checklist 1)Climate 2)Landform
3)Water 4)Access/Circulation 5)Vegetation and Wildlife
6)Microclimate 7)Buildings and Infrastructure 8)Zones of Use 9)Soil
Fertility and Management 10)Aesthetics/Experience of Place [Adapted
from P.A. Yeomans by David Jacke]. We can address things in this
order of priority and conduct design work and practical work in
this order (but not rigidly!)
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- 1) Climate plant hardiness zone predicted future climate change
status annual precipitation seasonal distribution latitude wind
directions prevailing, seasonal variations, storm wind directions
growing degree days (important for ripening nuts) average
frost-free dates chilling hours (important for fruit tree dormancy)
extreme weather potential: drought, flood, hurricane, tornado, fire
heating/cooling degree days
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- 2)Landform slope (steepness, rise/run in percent) topographic
position (i.e., mid-slope, hill crest, valley floor, etc.) bedrock
geology: permeability, depth, nutrient content, acidity surficial
geology: type of parent material, permeability, depth, stoniness,
nutrient content, acidity, suitability for various uses, etc.
estimated seasonal high water table depth estimated depth to
bedrock, hardpan or impermeable layers of soil elevation landslide
potential
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- 3) Water existing sources of supply: location, quantity,
quality, dependability, sustainability, network layout and features
(spigots, pipes, filters, etc.) watershed boundaries and flow
patterns: concentration and dispersion areas, including roof runoff
patterns, gutters and down spouts potential pollution sources: road
runoff, chemical runoff from neighbors, etc. flooding, ponding and
puddling areas possible sources of supply: location, quantity,
quality, dependability, sustainability, cost to develop location of
all on-site and nearby off-site culverts, wells, water lines,
sewage lines, septic systems, old wells, etc. erosion: existing and
potential areas
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- 4) Access/ Circulation activity nodes, storage areas
pedestrian, cart and vehicle access points, current and potential
patterns materials flows: mulch, compost, produce, firewood,
laundry, etc.
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- 5) Vegetation and Wildlife existing plant species: locations,
sizes, quantities, patterns, uses, poisonous, invasiveness,
weediness, what they indicate about site conditions, etc. ecosystem
architecture: layers and their density, patterning and diversity,
resultant habitat conditions, light/shade, character, quality
habitat types, food/water/shelter availability
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- 6)Microclimate define various microclimate spaces slope aspects
(direction slopes face relative to sun) sun/shade patterns cold air
drainage and frost pockets soil moisture patterns precipitation
patterns local wind patterns
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- 7)Buildings and Infrastructure building size, shape, locations
doors and windows, exist. and possible functions permanent pavement
and snow piles from plowing it power lines (above and below ground)
and electric outlets outdoor water faucet, septic system, well
locations location of underground pipes: water and sewer line,
footing drain, floor drain and down spout drain lines, tile drains,
culverts, other fences and gateways
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- 8) Zones of Use property lines, easements, rights-of-way
existing zones of land and water use well protection zones,
environmental and other legal limits (e.g. wetlands regulations,
zoning regulations, building setbacks) current uses by neighbors
and passersby use history and impacts on land, current or future
uses
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- 9)Soil Fertility and Management soil types: texture, structure,
consistence, profile, drainage topsoil fertility: pH, % OM, N, P,
K, Ca soil toxins: lead, mercury, cadmium, asbestos, etc..
management history soil testing: where to get it done, how to do
it
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- 10) Aesthetics/ Experience of Place outdoor rooms, walls:
define spaces (walls, ceilings, floors), qualities, feelings,
functions, features arrival and entry experience: sequencing,
spaces, eye movements, feelings
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- This is the type used in sand dams
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- Gleying a pond
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