FLOOD06195

• County: Statewide
• Community: State of Colorado
• Basin: Statewide
• Title: Measurment of Peak Discharge at Culverts by Indirect Methods
• Date: 6/1/1968
• Prepared By: G.L. Bodhaine
• Floodplain - Doc Type: Educational/Technical/Reference Information

0,06

TECHNIQUES OF WATER-RESOURCES INVESII'IGATIONS

26

0.05

0,04

u
"
~ "l~ 0.03
oi
-

Type 2

0,02

om

0,01

0,02

Critical slope (Sc),

Type 1

0,03
So

0,06

0,04

0,05

Figure 11.-Critical slope: for culverts of rectangular section, with free outfall.

Figures 12 and 13 are graphicsl solutions of
equation 14 for circular and riveted pipe-arch
sections. Figure 14 is the solution for square or
rectangular sections, These curves are based
on ponded approach conditions and the assump-
tion that V,= V,. Similar curves may be con-
structed for any given culvert shape, but the
development is so tedious that it generally is
not worthwhile.
In the event that approach velocity head and
friction loss cannot be neglected, the (h,-.)
term should be increased' by their algebraic
sum.
In long rough culverts V, is much larger than
V,; therefore,

V,' V,' (1 ) VI
2g0'<<2g+ 0,-1 2g'

(15)

The smaller the discharge coefficient, the
greater wiJI be the difference in d,. The d, com-
puted from figures 12, 13, and 14 may be greatly
in error when this condition exists. The proper
way to determine d, in this situation is by
routing. The routing method is described on
page 31.
The procedure outlined below is recom-
mended for computation of discharge,

Circular sed ions

Computation steps:
1. Com pu te 0 and enter figure 10 wi th
(h,- .)ID. Select the value of d,ID from
the appropriate curve.
2. Use 95 percent of d,ID as a first approxi-
mation to compute d" The 95 percent is

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