The handbook of Technical irrigaTion informaTion - Hunter Industries

Handbook of Technical Irrigation InformationSlopeGeneralSlope, as used in irrigation, is a measure of the incline of an area. It can be described as 1) a percent, formula “A”, 2)a degree, formulas “B” and “C”, or 3) a ratio, formula “D”. The greater the incline, the greater the tendency for runoff.A) The percent of slope can be determined by dividing the net change in elevation between two points (Rise) by thehorizontal distance between those two points (Run).Point “B”S = RiseRunPoint “A”Where:S = the percent of slopeRise = the net elevation change in elevation between two pointsRun = the horizontal distance between the two pointsRunRiseNote: The units for Rise and Run can be any unit of linear measure, but they must be the same for both the Riseand Run.Example:What is the slope for a bank 40 feet wide (run) on which the elevation at the top (point “B”) is 20 feet higher thanthe toe of the slope (point “A”)S = 20 S = 0.50 or 50%40B) The degree of slope describes a slope as the angle of the slope (at “A”) from the horizontal plane. This method isuseful when taking field measurements as “c” represents the measured distance up a slope and “a” equals the elevationchange.Point “B”casin A = a/cWhere:A = the anglea = the height of the right trianglec = the length of the hypotenuse of a right triangleExample:a = 20 feetc = 44.72 feetPoint “A”Angle at “A”Horizontal Planesin A = 20 sin A = 0.4472 A = 26° 34'44.722