Point C, is lower than A and the vertical distance between A and C is 1 m. For example, B is higher than A, and the vertical distance between A and B is 2 m. Any other point in the surrounding area is higher or lower than A, and the vertical distance between the two can be determined. In figure 51, point A is at the top of a concrete bridge. The main slope and cross slope of an irrigated field The thick arrow indicates the direction of what can be called the main slope the thin arrow indicates the direction of the cross slope, the latter crosses the direction of the main slope.Īn illustration of the main slope and the cross slope of an irrigated field is shown in Fig. Now, tilt the book sideways (6 cm) so that only one corner of it touches the table (Fig. Place a book on a table and lift one side of it 4 centimetres from the table (Fig. The following table shows a range of slopes commonly referred to in irrigated fields.įig. What is the difference in height between the top and the bottom of a field when the horizontal length of the field is 300 m and the slope is 2. What is the slope in percent and in per mil of a field with a horizontal length of 200 m and a height difference of 1.5 m between the top and the bottom?įield slope in = field slope in % x 10 = 0.75 x 10 = 7.5 47:įinally, the slope can be expressed in per mil the formula used is then: Using the same measurements shown in Fig. The slope can also be expressed in percent the formula used is then: It is the vertical distance, or difference in height, between two points in a field, divided by the horizontal distance between these two points. The slope of a field is expressed as a ratio. An accurate survey of the land is necessary to identify these so called "flat slopes". 46, white arrow).įlat areas are never strictly horizontal there are gentle slopes in a seemingly flat area, but they are often hardly noticeable to the naked eye. Go downhill, this is a falling slope (see Fig. Start climbing from the foot of a hill toward the top, this is called a rising slope (see Fig. It is important for the farmer or irrigator to identify the slopes on the land.Ī slope is easy to recognize in a hilly area. A slope is the rise or fall of the land surface.
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