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' REVISED <br />7/30/85 <br />' ~- Table 5 <br />' FISH CREEK TIPPLE <br />DIVERSIOPI )ITCH DESIGN CALCULATIONS (Continued) <br />' Ditch E-4 <br /> Tributary area = 12.6 a.:. watershed <br />' Weighted CN = 70 <br /> Total runoff @ CN(70) = 0.17 (in)/12 (in/ft) x 12.6 (ac.) = 0.18 ac-ft <br />' Peak flow (steep slope) 17.7 (cfs/in. runoff) x 0.17 (in. runoff) <br /> = 1.6 cfs uncorrected <br /> Basin slope factor (actual slope 26%) = 1.07 <br /> Basin shape factor (hydraulic length 760 ft., equivalent area 8.5 ac.) <br /> = 12.6/8.5 = 1.48 <br />' Corrected peak flow = 3..0 cfs x 1.07 x 1.48 = 4.75 cfs <br /> Design: trapezoidal ditch, 1.5 ft. deep, bott om width = 1.0 ft., <br />' side slopes = 2:1, gradient = 0.04 ft/ft, n = 0.03 <br /> Flow conditions: depth = 0.5 ft., velocity = 4.6 fps, ar ea <br /> <br />~ = 1.04 sq. ft. <br />' <br />° Check calculation: Q = VA = 4.6 x 1.04 = 4.78 cfs <br />' Ditch F-1 <br />Tributary area = 140 ac. undisturbed <br />Weighted CN = 70 <br />Total runoff @ CN(70) = 0.17 (in) / 12 (in/ft) x 140 (ac.) = 1.98 ac-ft <br />' Peak flow (steep slope) 225 (cfs/in. runoff) x 0.17 (in. runoff) <br />= 38.3 cfs uncorrected <br />' Basin slope factor (actual slope 10%) = 0.853 <br />Basin shape factor (hydraulic length 3,550 ft., equivalent area 115 ac.) <br />= 140/115 = 1.217 <br />' Corrected peak flow = 3f~.3 cfs x 0.853 x 1.217 = 39.8 cfs <br />Design: trapezoidal ditch, 3.0 ft. deep, bottom width = 2.0 ft., <br />' side slope = 2:1, gradient = 0.005 ft/f t, n = 0.03 <br />Flow conditions: depth = 1.90 ft., velocity = 3.62 fps, area <br />' = 10.98 sq. ft. <br />Check calculation: Q = VA = 3.62 x 10.98 = 39.75 cfs <br />1 z G ~~ ~ ~s <br />/ U -15- <br />