ASTM D5243-92(1996)

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
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Designation: D 5243 – 92 (Reapproved 1996)
Standard Test Method for
Open-Channel Flow Measurement of Water Indirectly at
Culverts
This standard is issued under the fixed designation D 5243; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope method, refer to Terminology D 1129.
3.2 Definitions of Terms Specific to This Standard—Several
1.1 This test method covers the computation of discharge
of the following terms are illustrated in Fig. 1:
(the volume rate of flow) of water in open channels or streams
3.2.1 alpha (a)—a velocity-head coefficient that adjusts the
using culverts as metering devices. In general, this test method
velocity head computed on basis of the mean velocity to the
does not apply to culverts with drop inlets, and applies only to
true velocity head. It is assumed equal to 1.0 if the cross section
a limited degree to culverts with tapered inlets. Information
is not subdivided.
related to this test method can be found in ISO 748 and ISO
3.2.2 conveyance (K)—a measure of the carrying capacity
1070.
of a channel and having dimensions of cubic feet per second.
1.2 This test method produces the discharge for a flood
3.2.2.1 Discussion—Conveyance is computed as follows:
event if high-water marks are used. However, a complete
stage-discharge relation may be obtained, either manually or 1.486
2 3
/
K 5 R A
n
by using a computer program, for a gage located at the
approach section to a culvert.
where:
1.3 The values stated in inch-pound units are to be regarded
n = the Manning roughness coefficient,
as the standard. The SI units given in parentheses are for
2 2
A = the cross section area, in ft (m ), and
information only.
R = the hydraulic radius, in ft (m).
1.4 This standard does not purport to address all of the
3.2.3 cross sections (numbered consecutively in down-
safety concerns, if any, associated with its use. It is the
stream order):
responsibility of the user of this standard to establish appro-
3.2.3.1 The approach section, Section 1, is located one
priate safety and health practices and determine the applica-
culvert width upstream from the culvert entrance.
bility of regulatory limitations prior to use.
3.2.3.2 Cross Sections 2 and 3 are located at the culvert
entrance and the culvert outlet, respectively.
2. Referenced Documents
3.2.3.3 Subscripts are used with symbols that represent
2.1 ASTM Standards:
cross sectional properties to indicate the section to which the
D 1129 Terminology Relating to Water
property applies. For example, A is the area of Section 1.
D 2777 Practice for Determination of Precision and Bias of
Items that apply to a reach between two sections are identified
Applicable Methods of Committee D-19 on Water
by subscripts indicating both sections. For example, h is the
f
1–2
D 3858 Practice for Open-Channel Flow Measurement of
friction loss between Sections 1 and 2.
Water by Velocity-Area Method
3.2.4 cross sectional area (A)—the area occupied by the
2.2 ISO Standards:
water.
ISO 748 Liquid Flow Measurements in Open Channels-
3.2.5 energy loss (h )—the loss due to boundary friction
3 f
Velocity-Area Methods
between two locations.
ISO 1070 Liquid Flow Measurements in Open Channels-
3.2.5.1 Discussion—Energy loss is computed as follows:
Slope-Area Methods
Q
h 5 L
S D
f
3. Terminology
K K
1 2
3.1 Definitions—For definitions of terms used in this test
where:
3 3
Q = the discharge in ft /s (m /s), and
This test method is under the jurisdiction of ASTM Committee D-19 on
L = the culvert length in ft (m).
Waterand is the direct responsibility of Subcommittee D19.07 on Sediments,
3.2.6 Froude number (F)—an index to the state of flow in
Geomorphology, and Open-Channel Flow.
the channel. In a rectangular channel, the flow is subcritical if
Current edition approved May 15, 1992. Published September 1992.
Annual Book of ASTM Standards, Vol 11.01.
the Froude number is less than 1.0, and is supercritical if it is
3 nd th
Available from American National Standards Institute, 11 W. 42 Street, 13
greater than 1.0.
Floor, New York, NY 10036.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
D 5243
NOTE 1—The loss of energy near the entrance is related to the sudden contraction and subsequent expansion of the live stream within the culvert barrel.
FIG. 1 Definition Sketch of Culvert Flow
3.2.6.1 Discussion—The Froude number is computed as the Manning equation for uniform flow and discharge coeffi-
follows: cients for the particular culvert to compute the discharge, Q,in
cubic feet (metres) per second.
V
F 5
gd
=
m
5. Significance and Use
5.1 This test method is particularly useful to determine the
where:
discharge when it cannot be measured directly with some type
V = the mean velocity in the cross section, ft/s (m/s),
of current meter to obtain velocities and sounding equipment to
d = the average depth in the cross section, in ft (m), and
m
2 2 determine the cross section. See Practice D 3858.
g = the acceleration due to gravity (32 ft/s ) (9.8 m/s ).
5.2 Even under the best of conditions, the personnel avail-
able cannot cover all points of interest during a major flood.
3.2.7 high-water marks—indications of the highest stage
The engineer or technician cannot always obtain reliable
reached by water including, but not limited to, debris, stains,
results by direct methods if the stage is rising or falling very
foam lines, and scour marks.
rapidly, if flowing ice or debris interferes with depth or velocity
3.2.8 hydraulic radius (R)—the area of a cross section or
measurements, or if the cross section of an alluvial channel is
subsection divided by the wetted perimeter of that section or
scouring or filling significantly.
subsection.
5.3 Under flood conditions, access roads may be blocked,
3.2.9 roughness coeffıcient (n)—Manning’s n is used in the
cableways and bridges may be washed out, and knowledge of
Manning equation.
the flood frequently comes too late. Therefore, some type of
3.2.10 velocity head (h )—is computed as follows:
v
indirect measurement is necessary. The use of culverts to
aV
determine discharges is a commonly used practice.
h 5
v
2g
6. Apparatus
where:
6.1 The equipment generally used for a “transit-stadia”
a = the velocity-head coefficient,
V = the mean velocity in the cross section, in ft/s (m/s), and survey is recommended. An engineer’s transit, a self-leveling
g = the acceleration due to gravity, in ft/s/s (m/s/s). level with azimuth circle, newer equipment using electronic
3.2.11 wetted perimeter (WP)—the length along the bound-
circuitry, or other advanced surveying instruments may be
ary of a cross section below the water surface. used. Necessary equipment includes a level rod, rod level, steel
and metallic tapes, survey stakes, and ample note paper.
4. Summary of Test Method
6.2 Additional items of equipment that may expedite a
4.1 The determination of discharge at a culvert, either after survey are tag lines (small wires with markers fixed at known
spacings), vividly colored flagging, axes, shovels, hip boots or
a flood or for selected approach stages, is usually a reliable
practice. A field survey is made to determine locations and waders, nails, sounding equipment, ladder, and rope.
elevations of high-water marks upstream and downstream from 6.3 A camera should be available to take photographs of the
the culvert, and to determine an approach cross section, and the culvert and channel. Photographs should be included with the
field data.
culvert geometry. These data are used to compute the eleva-
tions of the water surface and selected properties of the 6.4 Safety equipment should include life jackets, first aid
sections. This information is used along with Manning’s n in kit, drinking water, and pocket knives.
D 5243
7. Sampling of the tailwater, the entrance or barrel geometry, or a combi-
nation of these.
7.1 Sampling as defined in Terminology D 1129 is not
applicable in this test method. 9.2.3 Determine the discharge through a culvert by applica-
tion of the continuity equation and the energy equation
8. Calibration
between the approach section and a control section within the
8.1 Check adjustment of surveying instruments, transit, etc.,
culvert barrel. The location of the control section depends on
daily when in continuous use or after some occurrence that
the state of flow in the culvert barrel. For example: If critical
may have affected the adjustment.
flow occurs at the culvert entrance, the entrance is the control
8.2 The standard check is the “two-peg” or “double-peg”
section, and the headwater elevation is not affected by condi-
test. If the error is over 0.03 in 100 ft (0.091 m in 30.48 m),
tions downstream from the culvert entrance.
adjust the instrument. The two-peg test and how to adjust the
instrument are described in many surveying textbooks. Refer to
10. General Classification of Flow
manufacturers’ manual for the electronic instruments.
8.3 The “reciprocal leveling” technique (1) is considered 10.1 Culvert Flow— Culvert flow is classified into six types
the equivalent of the two-peg test between each of two on the basis of the location of the control section and the
successive hubs.
relative heights of the headwater and tailwater elevations to
8.4 Visually check sectional and telescoping level rods at
height of culvert. The six types of flow are illustrated in Fig. 2,
frequent intervals to be sure sections are not separated. A
and pertinent characteristics of each type are given in Table 1.
proper fit at each joint can be checked by measurements across
10.2 Definition of Heads—The primary classification of
the joint with a steel tape.
flow depends on the height of water above the upstream invert.
8.5 Check all field notes of the transit-stadia survey before
This static head is designated as h − z, where h is the height
1 1
proceeding with the computations.
above the downstream invert and z is the change in elevation of
the culvert invert. Numerical subscripts are used to indicate the
9. Description of Flow at Culverts
section where the head was measured. A secondary part of the
9.1 Relations between the head of water on and discharge
classification, described in more detail in Section 18, depends
through a culvert have been the subjects of laboratory inves-
on a comparison of tailwater elevation h to the height of water
tigations by the U.S. Geological Survey, the Bureau of Public
at the control relative to the downstream invert. The height of
Roads, the Federal Highway Administration, and many univer-
water at the control section is designated h .
sities. The following description is based on these studies and c
field surveys at sites where the discharge was known. 10.3 General Classifications—From the information in Fig.
9.2 The placement of a roadway fill and culvert in a stream
2, the following general classification of types of flow can be
channel causes an abrupt change in the character of flow. This
made:
channel transition results in rapidly varied flow in which
10.3.1 If h /D is equal to or less than 1.0 and ( h − z)/D is
4 1
acceleration due to constriction, rather than losses due to
less than 1.5, only Types 1, 2 and 3 flow are possible.
boundary friction, plays the primary role. The flow in the
10.3.2 If h /D and (h − z)/D are both greater than 1.0, only
4 1
approach channel to the culvert is usually tranquil and fairly
Type 4 flow is possible.
uniform. Within the culvert, however, the flow may be sub-
10.3.3 If h /D is equal to or less than 1.0 and ( h − z)/D is
critical, critical, or supercritical if the culvert is partly filled, or
4 1
equal to or greater than 1.5, only Types 5 and 6 flow are
the culvert may flow full under pressure.
9.2.1 The physical features associated with culvert flow are possible.
illustrated in Fig. 1. They are the approach channel cross
10.3.4 If h /D is equal to or greater than 1.0 on a steep
section at a distance equivalent to one opening width upstream
culvert and (h − z)/D is less than 1.0, Types 1 and 3 flows are
z
from the entrance; the culvert entrance; the culvert barrel; the
possible. Further identification of the type of flow requires a
culvert outlet; and the tailwater representing the getaway
trial-and-error procedure that takes time and is one of the
channel.
reasons use of the computer program is recommended.
9.2.2 The change in the water-surface profile in the ap-
proach channel reflects the effect of acceleration due to
11. Critical Depth
contraction of the cross-sectional area. Loss of energy near the
11.1 Specific Energy— In Type 1 flow, critical depth occurs
entrance is related to the sudden contraction and subsequent
at the culvert inlet, and in Type 2 flow critical flow occurs at the
expansion of the live stream within the barrel, and entrance
geometry has an important influence on this loss. Loss of culvert outlet. Critical depth, d , is the depth of water at the
c
energy due to barrel friction is usually minor, except in long point of minimum specific energy for a given discharge and
rough barrels on mild slopes. The important features that
cross section. The relation between specific energy and depth is
control the stage-discharge relation at the approach section can
illustrated in Fig. 3. The specific energy, H , is the height of the
o
be the occurrence of critical depth in the culvert, the elevation
energy grade line above the lowest point in the cross section.
Thus:
V
The boldface numbers in parentheses refer to a list of references at the end of
H 5 d 1
o
the text. 2g
D 5243
FIG. 2 Classification of Culvert Flow
TABLE 1 Characteristics of Flow Types
NOTE 1—D = maximum vertical height of barrel and diameter of circular culverts.
Location of h 2 z h h
1 4 4
Flow Type Barrel Flow Kind of Control Culvert Slope
Terminal Section
D h D
c
1 Partly full Inlet Critical depth Steep <1.5 <1.0 91.0
2 do Outlet do Mild <1.5 <1.0 91.0
3 do do Backwater do <1.5 >1.0 91.0
4 Full do do Any >1.0 . . . >1.0
5 Partly full Inlet Entrance geometry do :1.5 . . . 91.0
6 Full Outlet Entrance and barrel geometry do :1.5 . . . 91.0
where: where:
3 3
H = specific energy, Q = discharge, in ft /s (m /s),
o
d = maximum depth in the section, in ft, A = area of cross section below the water surface, ft
V = mean velocity in the section, in ft/s, and
2(m ),
2 2
g = acceleration of gravity (32 ft/s ) (9.8 m/s ).
T = width of the section at the water surface, in ft (m),
d = maximum depth of water in the critical-flow sec-
...