FLOOD01242

• County: Statewide
• Community: State of Colorado
• Stream Name: All
• Title: Hydraulic Design of Improved Inlets for Culverts
• Date: 9/1/1981
• Prepared For: USDOT
• Prepared By: Federal Highway Administration
• Floodplain - Doc Type: Educational/Technical/Reference Information

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Throat Control

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In order-to utilize more of the available culvert barrel
area, the control at design discharge generally should be at the
throat rather than at the face or crest. Chart 14 presents the
headwater depth, referenced to the throat invert, required to pass
a given discharge for side- or slope-tapered inlets operating in
throat control. This chart is in a semi-dimensionless form, Ht/D
plotted against Q/BD3/2. The term, Q/BD3/2, is not truly dimension-
less, but is a convenient parameter and can be made non-dimensional
by dividing by/the square root of gravitational acceleration, gl/2.
A table of BDj 2 values 1s contained in Section VIII.

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Face Control

e

Design curves for determining face width are provided in
Chart 15. Both the inlet edge condition and sidewall flare angle
affect the performance of the face section. The two curves 1n
Chart 15 pertain to the options in Figure 11. The dashed curve,
which is less favorable, applies to the following inlet edge
conditions:

(1) wingwall flares of 150 to 260 and a 1:1 top edge bevel,
and

(2)

wingwall
bevels) .
headwalL.

flares of 260 to 900 and square edges (no
A 900 wingwall flare is commonly termed a

The more desirable solid curve applies to the following entrance
conditions:

(1) wingwall flares of 260 to 450 with a 1:1 top edge bevel,
or

(2) wingwall flares of 450 to 900 with a 1:1 bevel on the
side and top edges.

.

Note that undesirable design features, such as wingwall
flare angles less than ISO, or 260 without a top bevel, are not
covered by the charts. Although the 1. 5: 1 bevels can be used,
due to structural considerations, the smaller 1:1 bevels are
preferred.

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