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

20

2
fo-
"'
'"
...
~
~
J:
f0-
Il.
'" 0,6
0
0,4

TECHNIQUES OF WATER-RESOURCES mVESTIGATIONS

/ / '// "h
/ / r//A
f;@W:-
. 'I i'
I ,
~ 'r -j--+ ,
I Iii I
L__.J i
.' ! in'
I '
Ll_ I -'

4

--- --,

r-i--'t

,

~j-

I ;...... ! //
I ' k;/
i-r- h~~~

0,2 ~~~~~I
~~i
0,1
0,1

0,2

0,4

0,6

I 2
AREA, IN SQUARE FEET

10

I IE

:::

"
D
N
~

10 I.:'::"~-':'-:~_-~::::',:' ::::: -=-FL Lrn::~::=::_- L '::::::c:r-'-'-Cp::;===--l
__~~ .--=, -- -j-- -t' -H--------t.---L--"t- jh . -j
I'--I-----~.- -, T -:-~--:; J
__' .: 0 'It
I ! . ",,-~- >.-
.I .f t'I') >. .0
,E~- _>._.o_C\l_
,.... ('<) .c Ln!
I c: N.o IX) ~
1- ., -+t- ,~- --~ 0 ///
I I I ~ Ii I :J "' '1/
~-----r---' ~-I;+/
"' I '" I

I )l~~~~

"
D
'"
-

I

--

4

6

J

20

Figure 5.-Depth-area curves for riveted pipe-arches.

showing properties of certain size pipes, and
pipe-arches. The purpose of these figures i, to
show the general shape these curves will follow
as well as to show certain type...; of curves t.hat
may be of vulue for sirnplifyill~ computntions
of odd-shaped culverts,

Flow at critical depth

At first glance, it may not be possible to tell
whether type 1, 2, or 3 (a backwater condition)
flow occurred. If the culvert is very steep and
the getaway conditions are good, the flow will
be type 1. For eulverts set on zero grade wit.h
good getaway conditions and no backwater,
type 2 flow is well assured. In both cases t.he '
type of flow must be proved, For fairly flat
slopes and when backwater may be a factor,
there is always the possibili t)' of type 3 flow

occurring. The following computational pro-
cedures will identify the type of flow,

Type 1 flow

The general procedure is to (1) assume that.
type 1 flow occurred, (2) compute the elevation
of t.he water surface at critical depth and the
critica.\ slope, and (3) compare the critical slope
with the bed slope, and the water-surface
elevation at critical dept.h with the tailwater
elevation. This will generally result in positive
identification of types 1 01' 3 flow or narrow the
possihle flow conditions to types 2 or 3,
If critical depth occurs at the inlet, the dis-
charge may be computed with the applicable
critical-depth equations, 1, 2, 3, 4, and the
energy equation 5 as written between the ap-
proach section and the inlet,

e

e

e