APPCOR11859

• Permit No: C1984062
• IBM Index Class Name: Application Correspondence
• Doc Date: 1/17/1983
• Doc Name: TR TO PN 76-16 FOR COMPLIANCE WITH WQCD
• Media Type: D
• Archive: No

' _
' DIVERSION DITCH DESIGNS
(Cont'd)
' Design: trapezoidal ditch, 1.5 ft. deep, bottom width = l.0 ft., side slopes 2:1,
' gradient = 0.04 ft/ft, n = 0.03
Flow conditions: depth = 0.5 ft., velocitry = 4.6 fps, area = 1.04 sq. ft.
' Check calculati~~: Q = VA = 4.6 x 1.04 = 4.78 cfs
Ditch F-1
' Tributary area = 140 ac. undisturbed
Weighted CN = 70
' Total runoff @ CN(70) = 0.17 (in) / 12 in/ft x 140 ac. = 1.98 ac-ft
Peak flow (steep slope) 225 cfs/in. runoff x 0.17 in runoff = 38.3 cfs uncorrected
' Basin slope factor (actual slope 10%) = 0.853
Basin shape factor (hydraulic length 3,550 ft., equivalent area 115 ac.) = 140/115 =
' 1.217
Corrected peak flow = 38.3 cfs x 0.853 x 1.217 = 39.8 cfs
' Design: trapezoidal ditch, 3.0 ft. deep, bottom width = 2.0 ft., side slopes 2:1,
gradient = 0.005 ft/ft, n = 0.03
' Flow conditions: depth = 1.90 ft., velocitry = 3.62 fps, area = 10.98 sq. ft.
Check calculation: Q = VA = 3.62 x 10.98 = 39.75 cfs
' Ditch F-2
Tributary area = 235 ac. undisturbed and reclaimed
' Weighted CN = 70
Total runoff @ CN(70) = 0.17 (in) / 12 in/ft x 235 ac. = 3.33 ac-ft
' Peak flow (steep slope) 150 cfs/in. runoff x 0.17 in runoff = 25.5 cfs uncorrected
Basin slope factor (actual slope 10%) = 0.859
' Basin shape factor (hydraulic length 4,200 ft., equivalent area 150 ac.) = 235/150 =
1.567
Corrected peak flow = 25.5 cfs x 0.859 x 1,567 = 34.3 cfs
Design: trapezoidal ditch, 3.0 ft. deep, bottom width = 2.0 ft., side slopes 2:1,
' gradient = 0.03 ft/ft, n = 0.03
Flow conditions: depth = 1.51 ft., velocitry = 4.51 fps, area = 7.60 sq. ft.
Check calculation: Q = VA = 4.51 x 7.60 = 34.3 cfs
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