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Peak discharge from <br />• the 10 year, 24 hour <br />10 year, 24 hour <br />25 year, 24 hour <br />Curve Number <br />the area is determined as follows for both <br />event and the 25 year, 24 hour event: <br />precipitation = 1.8 inches <br />precipitation = 2.2 inches <br />= 84 <br />LAG = 0.095 hrs. (from TR-55, Figure 3.3 for a slope of 7.8~ <br />and a length of 900 ft.) <br />Time of Concentration 1.667 x LAG = 0.158 hrs. (from TR55, <br />Figure 5.2 for TC 0.158 hrs., and area 0.011 sq. mi.) <br />Peak discharge, 10 yr., 24 hr, event 5.7 cfs <br />Peak discharge, 25 hr., 24 hr. event = 8.3 cfs <br />The two year sediment yield is determined by applying the <br />Universal soil loss equation (A-RKLSCP) to 5.5 acres of disturbed <br />area at the laydown area where: <br />• A = soil loss per unit area (tons/acre/yr). <br />R = The rain fall factor: is the number of erosion-index <br />units in a normal year's rain. <br />K =The soil erodibilitY factor: is the erosion rate per unit <br />of erosion index for a specific soil in cultivated continu- <br />ous fallow, on a 9 percent slope 72.6 feet long. <br />L = The slope-length factor: is the ratio of soil loss from <br />the field slope length to that from a 72.6 foot length on <br />the same soil type and gradient. <br />5 = The slope-gradient factor: is the ratio of soil loss <br />from the field gradient to that from a 9 percent slope. <br />n <br />D-6 <br />