FLOOD04208

• County: Statewide
• Basin: Statewide
• Title: Hydraulic Charts for the Selection of Highway Culverts
• Date: 12/1/1965
• Prepared By: Federal Highway Administration
• Floodplain - Doc Type: Educational/Technical/Reference Information

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Highway Culverts", by H. G. Boss';..!. Experimental data for box culverts
with headwalls and wingwalls were obtained frOlIl an unpublished report of
the U. S. Geological Survey.

These research data were analyzed and nOlIlographs for determining
culvert capacity for inlet control were develo:Qed by the Division of Hy-
draulic Research, Bureau of Public Roads. These nomographs, Charts 1
through 6, give headwater-discharge relationships for most conventional
culverts flowing with inlet control through a range of headwater depths
and discharges. Chart No.7, discussed on p. 5-13, is included in this
revised edition to stress the importance of improving 1;he inlets of cul-
verts flowing with inlet control.

Culverts Flowing With Outlet Control

Culverts flowing with outlet control can flow with the culvert bar-
rel full or part full for part of the barrel length or for all of it,
(see fig. 2). If.the entire cross section of the barrel is filled with
water for the total length of the barrel, the culvert is said to be in
full flow or flowing full, figures 2A .and 2B. Two other common types of
outlet-control flow are shown in figures 2C and 2D. The procedures given
in this circular provide methods for the accurate determination of head-
water depth for the flow conditions shown in figures 2A, 2B and 2C. The
method given for the part full flow condition, fig. 20, gives a solution
for headwater depth that decreases in accuracy as the headwater decreases.

The head H (fig. 2A) or energy required to pass a given quantity of
water through a culvert flowiug in outlet control with the barrel flowing
full throughout its length is made up of three major parts. These three
parts are usually expressed in feet of water and include a velocity head
Hv, an entrance loss He, and a friction loss Hf. This energy is obtained
frOlIl ponding of water at the entrance and expressed in equation form

H=Hv+He+Hf

(1)

The velocity head Hy equals ~, where V is the mean or average ve-

locity in the culvert barrel. (The mean velocity is the discharge Q, in
cfs, divided by the cross-sectional area A, in sq. ft., of the barrel.)

The entrance loss He depends upon the geometry of the inlet edge.
This loss is expressed as a coefficient ke times the barrel velocity
2
head or He = ke ~. The entrance loss coefficients ke for various types

of entrances when the flow is in outlet control are given in Appendix B,
Table 1, (p. 5-49).

Y Presented at the Tenth National Conference, Hydraulics Division,
A.S.C.E., August 1961.

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