TM 5-820-3/AFM 88-5, Chap. 3
APPENDIX C
OUTLET PROTECTION DESIGN PROBLEM
C-1. This appendix contains examples of recommended application to estimate the extent of scour in a
cohesionless soil and alternative schemes of protection required to prevent local scour.
C-2. Circular and rectangular outlets with equivalent cross-sectional areas that will be subjected to a range
of discharges for a duration of 1 hour are used with the following parameters:
Dimensions of rectangular outlet = Wo = 10 feet, Do = 5 feet
Diameter of circular outlet, Do = 8 feet
Range of discharge, Q = 362 to 1,086 cubic feet per second
Discharge parameter for rectangular culvert, q/Do3/2 = 3.2 to 9.7
Discharge parameter for circular culvert, Q/Do5/2 = 2 to 6
Duration of runoff event, t = 60 minutes
Maximum tailwater el = 6.4 feet above outlet invert (> 0.5 Do)
Minimum tailwater el = 2.0 feet above outlet invert (< 0.5 Do)
C-1
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