TM 5-820-3/AFM 88-5, Chap. 3
(13)
The feasibility of a paved channel
efficiency; if trapezoidal, they should be designed
with a slope compatible with that of the local
to have side slopes of lV on 3H and a depth-to-
terrain for conveyance of the design discharge at
width ratio of 0.3.
subcritical conditions should be investigated.
(14)
For example, assume a subcritical
However, it may not be feasible with slopes of 1
paved channel with a Manning's n of 0.015 and
percent or greater. Paved channels for subcritical
slope of 0.01 foot per foot is to be provided for a
conveyance of flows should be designed to provide
design discharge of 400 cubic feet per second. The
Froude numbers of flow ranging from about 0.25
maximum slope and discharge permissible for
to 0.8 to prevent excessive deposition and flow
conveying flow with a Froude number less than 0.8
instabilities, respectively, If rectangular, paved
in a hydraulically efficient rectangular channel with
channels should be designed to have a depth of
a minimum practical width of 1.0 foot can be
width radio as near 0.5 as practical for hydraulic
determined from figure D-6. For a D/B = 0.5 and
D-9
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