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Technical Revision 90-06 <br />• ~ The drainage height was calculated by subtracting the minimum and maximum <br />elevations within the contributing drainage area <br />~ The watershed hydraulic length was determined by a trial and error method of <br />plotting runoff flow paths within the drainage area and selecting the path with <br />the greatest total length <br />~ The equivalent drainage area was calculated by substituting the watershed <br />hydraulic length in the equation L = 209a°~° <br />~ A correction factor for watershed shape was calculated as the ratio between <br />the total contributing drainage area and the equivalent drainage area <br />~ The average watershed slope was determined by using the equation: <br />• 0.252 (IC25 + LC50 + LC751 <br />S = DA <br />Where: <br />S =average watershed slope in °~ <br />Z =drainage height in feet <br />LC25/50/75 = length of contour within the contributing <br />drainage area to 25, 50, and 75 percent of <br />the drainage height in feet <br />DA =drainage in square feet <br />~ A correction factor for watershed slope was determined from Appendix E of <br />SCS-Technical Release No. 55 <br />~ Equivalent peak discharge or each storm event was determined from the peak <br />discharge tables in SCS-Technical Release No. 55 (Type II Storm Distribution - <br />. Western Colorado) <br />TR 90-06 Exhibit 3 - 7 Revised 1 1 /16/90 <br />