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Keyline -A New Principle
THE Keyline plan embraces a system of progressive fertile soil developmentfor all crop and pasture lands as well as for the steeper and rougher lands thathave never before been capable of fast, economic improvement.
Its primary aim is the development of better soil structure, increasedsoil fertility and greater actual depth of fertile soil. It includes new cultivationtechniques; a method of farm subdivision and layout; planning for timber and scrubclearing and water conservation and irrigation. All are planned to facilitate orassist in the production of fertile soil.
The Keyline plan is based primarily on a particular line or linescalled Keylines. These lines and others related to them are used in all land developmentplanning and act as guides for farm working.
The first aim of Keyline is to provide simple means of conservingall the rain that falls on the land into the soil itself, retard its evaporation.rate and use this conserved moisture for the rapid production of soil, fertilityover both small and large areas of land.
The simplest form of a Keyline is illustrated in Map 1. This showsa valley formation by means of contour lines. The 180-foot contour line is the Keylineof this simple valley area.
The Keyline conception itself is a little technical, and an explanationof what this basic idea involves is given first.
A Keyline is a level or sloping line extended in both directions froma certain point in a valley, called the "Keypoint". This marks or dividesthe two types of relationship, always in the same vertical interval, that a valleybears to its adjacent ridges. In one of these relationships, that above the Keyline,the valley will be narrower and steeper generally than the adjacent ridges on eitherside of it. In the second relationship, existing below the Keyline, the valley willbe wider and flatter than its immediately adjacent ridges, or shoulders.
The approximate point of this relationship change in the valley isthe Keypoint of this valley. A line, either a true contour in both directions from,this point, or a gently sloping line rising in one direction and falling in the otherdirection (see later chapter)--from this Keypoint is the Keyline of this valley area.
Any property that includes in its area a watershed or water dividehas one or more Keylines.
In order to understand the full development and uses of this and otherKeylines, reference will be made to contour maps and particular contour lines ofthe maps. Not all readers will have had experience of these maps and their contourlines, but the following description will make the later references clear.
Contour lines, or contours, are lines on maps or marked on the landitself to show particular levels. Map 1 is a simple contour map and the contour lineson the map mark the levels.
All points on the lines marked with the various heights are the sameheight as indicated by the figures. Thus on the 200-foot contour line all pointsare 200 feet above "datum". Datum is very often mean sea-level, but maybe any other permanent point.
A contour line lies at right angles to the slope of the land; as theslope changes direction the contour lines curve and turn. Contour lines on a contourmap are placed at regular vertical heights apart. The distance apart is called thevertical interval. On farm contour maps these range from 25 feet to 2 feet, accordingto the type of land formation and accuracy desired. On Map 1 they are 10 feet apartvertically. The space or interval between two contour lines is referred to as a contourstrip.
A contour map exhibits the formation of land by means of contour lines.
The contour Map 1 exhibits a simple valley formation. The centre lineof the valley floor is indicated by a dotted line and the downhill slope by an arrow.
The 220-foot contour is near the top of a watershed or water divide.The valley formation starts between the 210- and 200-foot contours, as indicatedby these two contour lines coming closer together near the dotted line of the valley.The actual slope here is steeper than that on either side between the same two contourlines. This is the valley head. The valley steepens a little more between the 200-and 190-foot contours, as indicated by these two lines being closer together thanthe 210- and 200-foot contours. The slope of the valley then remains constant tothe 180-foot contour in the valley. This is indicated on the map by the distancesbetween the 200- and 190-foot contours and between the 190- and 180-foot contourlines at the centre valley point being approximately equal. At this point, wherethe 180-foot contour line crosses the dotted line of the valley bottom, a changetakes place in the character of the valley formation. The valley bottom flattensconsiderably, as indicated by the greatly increased distance in the valley bottombetween contour lines 180 and 170 feet.
The whole relationship of the valley to its adjacent ridges in eachcontour strip has also changed.
Above the 180-foot contour line the valley bottom is steeper and narrowerthan its adjacent ridges in the contour strips, but below the 180-foot contour linethe valley is flatter and wider, in the contour strips, than its adjacent ridges.The slope relationship between this valley and the adjacent ridges continues throughthe lower contour strips of the map.
As a general rule, the relationship is constant for the remainderof a valley. The line of this change of relationship between the valley and its adjacentridges in each contour strip is the Keyline of this valley. The position or pointof this change in the valley itself is the Keypoint of the valley.
My own discovery, study and use of this -peculiar significance, relatingto the varying valley and ridge forms, is the basis of the Keyline plan. Its usein farming and general land planning and development is discussed throughout thisbook. A study of the topographical geography of general land formation will showa remarkable consistency and regularity in this changing relationship between valleysand their adjacent ridges.
The crucial point of change in the valley floor slope, the Keypoint,may coincide with the confluence of two or more valleys.
At the Keyline the line of the valley floor and adjacent ridge slopeare neutral.
Various types of land formations lend differing forms to their Keylines,but generally the significant valley and ridge relationship is consistent in thewidest variations of land formations.
It is important to keep in mind that the valley area in the contourstrip above the Keyline is narrower generally than the adjacent ridge area and thatthe valley area in any contour strip below the Keyline is wider generally than theadjacent ridge area of the same contour strip.
The 180-foot contour line of Map 1 is the simplest form of Keyline--theKeyline of a single valley. Keylines, as discussed here for farm work, are not locatedon the very small scale contour maps of large land areas, such as inch-to-the-mileland plans. Maps that have sufficient contours to exhibit accurately every valleyon a medium size property will, however, enable the Keylines to be located quiteclearly.
Before explaining the full development of Keyline, this simple formis used in the next chapter to illustrate a practical application of the Keylineprinciple.