ASTM D5388-93(2013)

Standard Test Method for Indirect Measurements of Discharge by Step-Backwater Method

SIGNIFICANCE AND USE
5.1 This test method is particularly useful for determining the discharge when it cannot be measured directly (such as during high flow conditions) by some type of current meter to obtain velocities and with sounding weights to determine the cross section (refer to Test Method D3858). This test method requires only one high-water elevation, unlike the slope-area test method that requires numerous high-water marks to define the fall in the reach. It can be used to determine a stage-discharge relation without needing data from several high-water events.  
5.1.1 The user is encouraged to verify the theoretical stage-discharge relation with direct current-meter measurements when possible.  
5.1.2 To develop a rating curve, plot stage versus discharge for several discharges and their computed stages on a rating curve together with direct current-meter measurements.
SCOPE
1.1 This test method covers the computation of discharge of water in open channels or streams using representative cross-sectional characteristics, the water-surface elevation of the upstream-most cross section, and coefficients of channel roughness as input to gradually-varied flow computations.2  
1.2 This test method produces an indirect measurement of the discharge for one flow event, usually a specific flood. The computed discharge may be used to define a point on the stage-discharge relation.  
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.

General Information

• Status: Historical
• Publication Date: 31-Dec-2012
• ICS: 17.220.20 - Measurement of electrical and magnetic quantities
• Technical Committee: D19 - Water
• Drafting Committee: D19.07 - Sediments, Geomorphology, and Open-Channel Flow

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:D5388 −93 (Reapproved 2013)
Standard Test Method for
Indirect Measurements of Discharge by Step-Backwater
1
Method
This standard is issued under the fixed designation D5388; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope D3858 Test Method for Open-Channel Flow Measurement
of Water by Velocity-Area Method
1.1 This test method covers the computation of discharge of
water in open channels or streams using representative cross-
3. Terminology
sectional characteristics, the water-surface elevation of the
upstream-most cross section, and coefficients of channel 3.1 Definitions:
2
roughness as input to gradually-varied flow computations.
3.1.1 For definitions of terms used in this test method, refer
to Terminology D1129.
1.2 This test method produces an indirect measurement of
3.2 Definitions of Terms Specific to This Standard:
the discharge for one flow event, usually a specific flood. The
NOTE—Several of the following terms are illustrated in Fig.
computed discharge may be used to define a point on the
1.
stage-discharge relation.
3.2.1 alpha (α)—a dimensionless velocity-head coefficient
1.3 The values stated in inch-pound units are to be regarded
that represents the ratio of the true velocity head to the velocity
as the standard. The SI units given in parentheses are for
head computed on the basis of the mean velocity. It is assumed
information only.
equal to unity if the cross section is not subdivided. For
1.4 This standard does not purport to address all of the
subdivided sections, α is computed as follows:
safety concerns, if any, associated with its use. It is the
3
k
i
responsibility of the user of this standard to establish appro-
2
(
a
i
priate safety, health, and environmental practices and deter-
α 5 (1)
3
K
T
mine the applicability of regulatory limitations prior to use.
2
A
T
1.5 This international standard was developed in accor-
dance with internationally recognized principles on standard-
where:
ization established in the Decision on Principles for the
k and a = the conveyance and area of the subsection indi-
Development of International Standards, Guides and Recom-
cated by the subscript I, and
mendations issued by the World Trade Organization Technical
K and A = theconveyanceandareaofthetotalcrosssection
Barriers to Trade (TBT) Committee.
indicated by the subscript T.
3.2.2 conveyance(K)—ameasureofthecarryingcapacityof
2. Referenced Documents
a channel without regard to slope and has dimensions of cubic
3
2.1 ASTM Standards:
feet per second. Conveyance is computed as follows:
D1129 Terminology Relating to Water
1.49
D2777 Practice for Determination of Precision and Bias of 2/3
K 5 AR (2)
n
Applicable Test Methods of Committee D19 on Water
3.2.3 cross-section area (A)—theareaatthewaterbelowthe
water-surface elevation that it computed. The area is computed
1
This test method is under the jurisdiction of ASTM Committee D19 on Water
as the summation of the products of mean depth multiplied by
and is the direct responsibility of Subcommittee D19.07 on Sediments,
the width between stations of the cross section.
Geomorphology, and Open-Channel Flow.
Current edition approved Jan. 1, 2013. Published January 2013. Originally
3.2.4 cross sections (numbered consecutively in downstream
approved in 1993. Last previous edition approved in 2007 as D5388 – 93 (2007).
order)—representative of a reach and channel and are posi-
DOI: 10.1520/D5388-93R13.
2
tioned as nearly as possible at right angles to the direction of
Barnes, H. H., Jr., “Roughness Characteristics of Natural Streams,” U.S.
Geological Survey Water Supply Paper 1849, 1967.
flow. They must be defined by coordinates of horizontal
3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
distance and ground elevation. Sufficient ground points must
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
be obtained so that straight-line connection of the coordinates
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. will adequately describe the cross-section geometry.
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1

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D5388−93 (2013)
V
F 5 (7)
=gdm
where:
V = the mean velocity, ft/s (m/s),
dm = the mean depth in the cross section, feet, and
g = the acceleration of gravity, ft/s/s (m/s/s).
3.2.9 hydraulic radius (R)—defined as the area of a cross
section or subsection divided by the corresponding wetted
perimeter. The wetted perimet
...