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   The contour lines of Nature's seas and lakes have been borrowed and are used as a device by the many professions concerned with land-use, so as to illustrate in a practical and accurate manner on paper, the shapes and the forms of land surfaces.

   A contour line surrounds the land. A contour line surrounds the water--of lakes and ponds. The water line around a swimming pool or a bath are contour lines.

   For the purpose of illustrating land on paper, the lines are used on 'contour' maps where the individual contour lines show where the land is the same height as indicated by the contours. The lines are placed to show set vertical distances below each other, such as one foot or ten feet.

   On a map the highest contour line is placed as if all the contour lines which indicate lower land, were under the water of an imaginary lake and this first contour line was part of the shoreline of the lake or of an island in the lake. The next contour line of the map, say ten feet vertically lower than the top line, is again part of the shoreline when the water of the lake has dropped ten feet--and so on downwards.

   The contour lines on a map show the shapes and the forms of the land and the positions and relationships of water courses and ponds. They show also how water will behave anywhere on the land, because the natural path of water flowing over the surface is always at right angles to the contours of the land. This natural path of water is the steepest and fastest route, but it is never a straight line; it always forms a flat S curve from ridge to valley.

   The main ridge is the top of the land, the backbone and the outline of the landscape. Look again at the skyline!

   The contour diagram of the main ridge displays the contours as a series of elongated loops, one outside the other downwards, with the distance from loop to loop wider at the crest line of the main ridge and narrower elsewhere.

   The head of the primary valley intrudes into this contour pattern of the main ridge where part of a contour line swings in closer to the contour line above. The change of pattern shows the first slope at the head of the primary valley to be steeper than the nearby slope of the main ridge.

   The elongated loop pattern of the main ridges changes to a series of flatter loop patterns of the primary ridges between the closer together contours at the head of the primary valleys. The loop pattern of the primary ridge contours approach more the shape of the arcs of a circle than the hair-pin like loops of the main ridge. The contours are widest apart at the centre or divide line of the primary ridge and narrowest at the head of the primary valley.

   The primary valley has two slopes which change from steep to much flatter at the Keyline of the valley.

   At the Keyline the contour pattern changes. The contours become closer together near the primary valley before they open out to display the flatter slope of the primary valley below the Keyline. Then they converge again on the other side of the primary valley to open out again to display the next primary ridge shape. A line through the contours, joining the points of greatest convergence on each side of the primary valley, marks the boundary between valley and ridge shape.

   This combined contour pattern of the three shapes of the land may change again near the creek below, by the contours coming closer together near the centre of the primary ridge and being wider apart in the primary valley. This new pattern indicates that the primary ridge has 'nosed over' just above its lower boundary--the creek below.

   The land forms of hill, saddle and pond also have their contour patterns. If there is a saddle in the main ridge at the level, say, of the second contour, the two top contours will be elongated ovals to display the hill on the main ridge. Near the saddle they may be closer together or sometimes further apart. A saddle point is always on the crest line (water-divide line) of a ridge. A saddle point can be, on iiiiiioccasions, the Keypoint of a primary valley or more often be at the top of the first steep slope of a primary valley. A hill on a primary ridge will have the same closed contours, each outside the other, but with the oval form less pronounced or gone altogether.

   From a saddle point, contours go four ways. If there is another saddle at the same height or lower, the contours join up and form a figure 8.

   The contour diagram of a pond displays the same pattern as for a hill, but the inside contour is the lowest line and the outside contour, the highest.

   Since the main ridge rises into the rising country towards the head of the watershed, the height of the Keylines of the series of primary valleys tend to have a rising relationship also.

   The creek is the lower boundary of its tributary primary valleys and of the primary ridges on each side of the primary valleys.

   Run-off water from rainfall on the main ridge and the higher parts of the primary ridges, flows to the primary valley by the steepest path and the fastest route. The pattern of flow is at right angles to the contours. The contour diagram illustrates that the steepest slopes of land are in the primary valley above the Keyline. The contours show also that the run-off from rain converges from the steep head of the primary valley to concentrate at the Keypoint. Therefore the stability and permanence of the natural landscapes depend largely on the fertility and thus the strength of the primary valley to resist the force of flowing water.

   The combined contour diagram of the land illustrates further, the paramount efficiency of Nature's landscape design for getting rid of water quickly.

   If you look for a primary valley in the city you may not recognise it so easily. It has been disguised by being overlooked and by our education which ignores it. Even if you look at a primary valley in the cleared countryside you will not see the Keyline, unless a farmer has marked it with a water channel or has disclosed it with the water line of a farm dam. But you may discern the. Keypoint where the two slopes of the primary valley meet.

   If you do go out in the country and find the Keypoint of a primary valley and stand there, you will see the family place of the three shapes of land where they meet; you may look upwards and see THE AMPHITHEATRE OF THE LANDSCAPE. If this place were filled with people, you would be the centre of all eyes--the centre of the stage. In the same way, if a sheet of water flowed from all around the highest tier of the theatre, you would cop the lot.

   The functions of the primary valleys in the landscape have been overlooked by those who were responsible for devising the special purpose landscapes of man--with one exception. By accident or by instincts developed from long and intimate association with land, a few farming families have improved and strengthened the primary valleys. In doing so they increased the fertility and the durability of their farmscape.

   There are thus special characteristics disclosed by Nature's landscape design for consideration when we attempt to superimpose on them the special purpose

   landscapes for ourselves. There is the efficiency of the shapes of land for getting rid of water and the only way water is retained for the benefit of the land, by being slowed down and some of it being stored by the soil, the grass and the trees--by all the life in the landscape. Then the water which falls as rain on all the ridges, which occupy so. much of the land, flows as run-off to concentrate in the primary valleys which are so little of the land surface; yet the value of land--rural land in Australia certainly--is as high as 80% a water value.

   Water flows from farming land in the same efficient manner as it does from the natural landscapes. Therefore much water passes without being used effectively in the landscape. NATURAL WASTE PRODUCTS FROM PLANTS AND ANIMALS AND FROM ARTIFICIAL SUBSTANCES USED ON THE FARM, ARE RUSHED TO THE WATER COURSES TO POLLUTE THE COMMON WATERS OF THE LAND AND THE SEAS. This type of pollution, when it does not contain artificial substances, is named Primitive Pollution.

   The natural landscapes had come to terms with the water. A state of balance existed which was in accord with the amount of water available to the land. Where the rainfall was high and reliable, rain forests had developed; where the rainfall was moderate and its incidence less reliable, the grasslands of nature were found. When the man-made landscapes of farm and city were imposed on those of nature, the balance of the association of land and water was changed. The flow of water off the land was speeded-up, instead of being slowed down.

   It is evident that landscape design must firstly be concerned with water to (1), to control positively and to use more effectively the water which flows from the land to the water courses and (2), to improve on or change the pattern of behaviour of water which falls on the ridge shapes.

   The design which achieves the optimum control and beneficial use of water for the development of high fertility, efficiency and balance for the farmscape, will be the logical design for townscape and cityscape and for all the special purposes landscapes of man. And the control and better use of water is the first answer for the control and final elimination of pollution.

   The life in the landscape of Nature was principally a process of slowly moving water: even our own bodies are 70% water. Nature slowed down the water, with the life of the landscape. Surely the next step which is up to us is to control and to use every drop of water before it reaches the streams and the rivers, for the aggrandisement of all the special purpose landscapes of man.