ASTM D5243-92(2001)
(Test Method)Standard Test Method for Open-Channel Flow Measurement of Water Indirectly at Culverts
Standard Test Method for Open-Channel Flow Measurement of Water Indirectly at Culverts
SCOPE
1.1 This test method covers the computation of discharge (the volume rate of flow) of water in open channels or streams using culverts as metering devices. In general, this test method does not apply to culverts with drop inlets, and applies only to a limited degree to culverts with tapered inlets. Information related to this test method can be found in ISO 748 and ISO 1070.
1.2 This test method produces the discharge for a flood event if high-water marks are used. However, a complete stage-discharge relation may be obtained, either manually or by using a computer program, for a gage located at the approach section to a culvert.
1.3 The values stated in inch-pound units are to be regarded as the standard. The SI units given in parentheses are for information only.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D 5243 – 92 (Reapproved 2001)
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.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope ISO 748 Liquid Flow Measurements in Open Channels-
Velocity-Area Methods
1.1 This test method covers the computation of discharge
ISO 1070 Liquid Flow Measurements in Open Channels-
(the volume rate of flow) of water in open channels or streams
Slope-Area Methods
using culverts as metering devices. In general, this test method
does not apply to culverts with drop inlets, and applies only to
3. Terminology
a limited degree to culverts with tapered inlets. Information
3.1 Definitions—For definitions of terms used in this test
related to this test method can be found in ISO748 and
method, refer to Terminology D1129.
ISO1070.
3.2 Definitions of Terms Specific to This Standard—Several
1.2 This test method produces the discharge for a flood
of the following terms are illustrated in Fig. 1:
event if high-water marks are used. However, a complete
3.2.1 alpha (a)—a velocity-head coefficient that adjusts the
stage-discharge relation may be obtained, either manually or
velocity head computed on basis of the mean velocity to the
by using a computer program, for a gage located at the
truevelocityhead.Itisassumedequalto1.0ifthecrosssection
approach section to a culvert.
is not subdivided.
1.3 The values stated in inch-pound units are to be regarded
3.2.2 conveyance (K)—a measure of the carrying capacity
as the standard. The SI units given in parentheses are for
of a channel and having dimensions of cubic feet per second.
information only.
3.2.2.1 Discussion—Conveyance is computed as follows:
1.4 This standard does not purport to address all of the
1.486
safety concerns, if any, associated with its use. It is the
2 3
/
K 5 R A
n
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
where:
bility of regulatory limitations prior to use.
n = the Manning roughness coefficient,
2 2
A = the cross section area, in ft (m ), and
2. Referenced Documents
R = the hydraulic radius, in ft (m).
2.1 ASTM Standards:
3.2.3 cross sections (numbered consecutively in down-
D 1129 Terminology Relating to Water
stream order):
D 2777 Practice for Determination of Precision and Bias of
3.2.3.1 The approach section, Section 1, is located one
Applicable Methods of Committee D-19 on Water
culvert width upstream from the culvert entrance.
D 3858 Practice for Open-Channel Flow Measurement of
3.2.3.2 Cross Sections 2 and 3 are located at the culvert
Water by Velocity-Area Method
entrance and the culvert outlet, respectively.
2.2 ISO Standards:
3.2.3.3 Subscripts are used with symbols that represent
cross sectional properties to indicate the section to which the
1 property applies. For example, A is the area of Section 1.
This test method is under the jurisdiction ofASTM Committee D-19 on Water
and is the direct responsibility of Subcommittee D19.07 on Sediments, Geomor-
phology, and Open-Channel Flow.
3 nd th
Current edition approved May 15, 1992. Published September 1992. AvailablefromAmericanNationalStandardsInstitute,11W.42 Street,13
Annual Book of ASTM Standards, Vol 11.01. Floor, New York, NY 10036.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 5243 – 92 (2001)
NOTE 1—Thelossofenergyneartheentranceisrelatedtothesuddencontractionandsubsequentexpansionofthelivestreamwithintheculvertbarrel.
FIG. 1 Definition Sketch of Culvert Flow
Items that apply to a reach between two sections are identified
aV
h 5
v
by subscripts indicating both sections. For example, h is the 2g
f
1–2
friction loss between Sections 1 and 2.
where:
3.2.4 cross sectional area (A)—the area occupied by the
a = the velocity-head coefficient,
water.
V = themeanvelocityinthecrosssection,inft/s(m/s),and
3.2.5 energy loss (h)—the loss due to boundary friction
f
g = the acceleration due to gravity, in ft/s/s (m/s/s).
between two locations.
3.2.11 wetted perimeter (WP)—thelengthalongthebound-
3.2.5.1 Discussion—Energy loss is computed as follows:
ary of a cross section below the water surface.
Q
h 5 L
S D
f
K K 4. Summary of Test Method
1 2
4.1 The determination of discharge at a culvert, either after
where:
3 3 a flood or for selected approach stages, is usually a reliable
Q = the discharge in ft /s (m /s), and
practice. A field survey is made to determine locations and
L = the culvert length in ft (m).
elevationsofhigh-watermarksupstreamanddownstreamfrom
3.2.6 Froude number (F)—an index to the state of flow in
theculvert,andtodetermineanapproachcrosssection,andthe
the channel. In a rectangular channel, the flow is subcritical if
culvert geometry. These data are used to compute the eleva-
the Froude number is less than 1.0, and is supercritical if it is
tions of the water surface and selected properties of the
greater than 1.0.
sections. This information is used along with Manning’s n in
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
V
cubic feet (metres) per second.
F 5
gd
=
m
5. Significance and Use
where:
5.1 This test method is particularly useful to determine the
V = the mean velocity in the cross section, ft/s (m/s),
discharge when it cannot be measured directly with some type
d = the average depth in the cross section, in ft (m), and
m ofcurrentmetertoobtainvelocitiesandsoundingequipmentto
2 2
g = the acceleration due to gravity (32 ft/s ) (9.8 m/s ).
determine the cross section. See Practice D3858.
5.2 Even under the best of conditions, the personnel avail-
3.2.7 high-water marks—indications of the highest stage
able cannot cover all points of interest during a major flood.
reached by water including, but not limited to, debris, stains,
The engineer or technician cannot always obtain reliable
foam lines, and scour marks.
results by direct methods if the stage is rising or falling very
3.2.8 hydraulic radius (R)—the area of a cross section or
rapidly,ifflowingiceordebrisinterfereswithdepthorvelocity
subsection divided by the wetted perimeter of that section or
measurements, or if the cross section of an alluvial channel is
subsection.
scouring or filling significantly.
3.2.9 roughness coeffıcient (n)—Manning’s n is used in the
5.3 Under flood conditions, access roads may be blocked,
Manning equation.
cableways and bridges may be washed out, and knowledge of
3.2.10 velocity head (h )—is computed as follows: the flood frequently comes too late. Therefore, some type of
v
D 5243 – 92 (2001)
indirect measurement is necessary. The use of culverts to approach channel to the culvert is usually tranquil and fairly
determine discharges is a commonly used practice. uniform. Within the culvert, however, the flow may be sub-
critical, critical, or supercritical if the culvert is partly filled, or
6. Apparatus
the culvert may flow full under pressure.
9.2.1 The physical features associated with culvert flow are
6.1 The equipment generally used for a “transit-stadia”
survey is recommended. An engineer’s transit, a self-leveling illustrated in Fig. 1. They are the approach channel cross
level with azimuth circle, newer equipment using electronic section at a distance equivalent to one opening width upstream
circuitry, or other advanced surveying instruments may be from the entrance; the culvert entrance; the culvert barrel; the
used.Necessaryequipmentincludesalevelrod,rodlevel,steel culvert outlet; and the tailwater representing the getaway
and metallic tapes, survey stakes, and ample note paper. channel.
6.2 Additional items of equipment that may expedite a 9.2.2 The change in the water-surface profile in the ap-
survey are tag lines (small wires with markers fixed at known proach channel reflects the effect of acceleration due to
spacings), vividly colored flagging, axes, shovels, hip boots or contraction of the cross-sectional area. Loss of energy near the
waders, nails, sounding equipment, ladder, and rope. entrance is related to the sudden contraction and subsequent
6.3 Acamerashouldbeavailabletotakephotographsofthe expansion of the live stream within the barrel, and entrance
geometry has an important influence on this loss. Loss of
culvert and channel. Photographs should be included with the
field data. energy due to barrel friction is usually minor, except in long
rough barrels on mild slopes. The important features that
6.4 Safety equipment should include life jackets, first aid
kit, drinking water, and pocket knives. control the stage-discharge relation at the approach section can
be the occurrence of critical depth in the culvert, the elevation
7. Sampling
of the tailwater, the entrance or barrel geometry, or a combi-
nation of these.
7.1 Sampling as defined in Terminology D1129 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
culvert barrel. The location of the control section depends on
8.1 Checkadjustmentofsurveyinginstruments,transit,etc.,
the state of flow in the culvert barrel. For example: If critical
daily when in continuous use or after some occurrence that
flow occurs at the culvert entrance, the entrance is the control
may have affected the adjustment.
section, and the headwater elevation is not affected by condi-
8.2 The standard check is the “two-peg” or “double-peg”
tions downstream from the culvert entrance.
test. If the error is over 0.03 in 100 ft (0.091 m in 30.48 m),
adjust the instrument. The two-peg test and how to adjust the
10. General Classification of Flow
instrumentaredescribedinmanysurveyingtextbooks.Referto
10.1 Culvert Flow—Culvertflowisclassifiedintosixtypes
manufacturers’ manual for the electronic instruments.
on the basis of the location of the control section and the
8.3 The “reciprocal leveling” technique (1) is considered
relative heights of the headwater and tailwater elevations to
the equivalent of the two-peg test between each of two
height of culvert.The six types of flow are illustrated inFig. 2,
successive hubs.
and pertinent characteristics of each type are given in Table 1.
8.4 Visually check sectional and telescoping level rods at
10.2 Definition of Heads—The primary classification of
frequent intervals to be sure sections are not separated. A
flowdependsontheheightofwaterabovetheupstreaminvert.
properfitateachjointcanbecheckedbymeasurementsacross
This static head is designated as h − z, where h is the height
1 1
the joint with a steel tape.
abovethedownstreaminvertand zisthechangeinelevationof
8.5 Check all field notes of the transit-stadia survey before
theculvertinvert.Numericalsubscriptsareusedtoindicatethe
proceeding with the computations.
section where the head was measured.Asecondary part of the
9. Description of Flow at Culverts classification, described in more detail in Section 18, depends
onacomparisonoftailwaterelevation h totheheightofwater
9.1 Relations between the head of water on and discharge
at the control relative to the downstream invert. The height of
through a culvert have been the subjects of laboratory inves-
water at the control section is designated h .
c
tigations by the U.S. Geological Survey, the Bureau of Public
10.3 General Classifications—From the information in Fig.
Roads,theFederalHighwayAdministration,andmanyuniver-
2, the following general classification of types of flow can be
sities. The following description is based on these studies and
made:
field surveys at sites where the discharge was known.
10.3.1 If h /D is equal to or less than 1.0 and ( h − z)/D is
4 1
9.2 The placement of a roadway fill and culvert in a stream
less than 1.5, only Types 1, 2 and 3 flow are possible.
channel causes an abrupt change in the character of flow. This
10.3.2 If h /D and (h − z)/D are both greater than 1.0, only
channel transition results in rapidly varied flow in which 4 1
Type 4 flow is possible.
acceleration due to constriction, rather than losses due to
10.3.3 If h /D is equal to or less than 1.0 and ( h − z)/D is
boundary friction, plays the primary role. The flow in the 4 1
equal to or greater than 1.5, only Types 5 and 6 flow are
possible.
10.3.4 If h /D is equal to or greater than 1.0 on a steep
The boldface numbers in parentheses refer to a list of references at the end of 4
the text. culvert and (h − z)/D is less than 1.0, Types 1 and 3 flows are
z
D 5243 – 92 (2001)
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
possible. Further identification of the type of flow requires a 11.2 Relation Between Discharge and Depth—It can be
trial-and-error procedure that takes time and is one of the shown that at the point of minimum specific energy, that is, at
reasons use of the computer program is recommended. critical depth, d , there is a unique relation between discharge
c
(or velocity) and depth as shown by the following equations:
11. Critical Depth
2 3
Q A
11.1 Specific Energy— In Type 1 flow, critical depth occurs
g T
attheculvertinlet,andinType2flowcriticalflowoccursatthe
and:
culvert outlet. Critical depth, d , is the depth of water at the
c
V A
point of minimum specific energy for a given discharge and
5 d 5
m
g T
crosssection.Therelationbetweenspecificenergyanddepthis
illustratedinFig.3.Thespecificenergy, H ,istheheightofthe
o
energy grade line above the lowest point in the cross section.
where:
Thus: 3 3
Q = discharge, in ft /s (m /s),
A = area of cross section below the water surface, ft
V
H 5 d 1
o
2(m ),
2g
T = width of the section at the water surface, in ft (m),
where:
d = maximum depth of water in the critical-flow sec-
c
H = specific energy,
o tion, in ft (m), and
d = maximum depth i
...
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