ASTM D5388-93(1997)

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

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.
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 problems, 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: 09-Dec-1997
• Technical Committee: D19 - Water
• Drafting Committee: D19.07 - Sediments, Geomorphology, and Open-Channel Flow

Relations

• Replaced By: ASTM D5388-93(2002) - Standard Test Method for Indirect Measurements of Discharge by Step-Backwater Method
• Effective Date: 15-Apr-1993

Standards Content (Sample)

Designation: D 5388 – 93 (Reapproved 1997)
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Test Method for
Indirect Measurements of Discharge by Step-Backwater
1
Method
This standard is issued under the fixed designation D 5388; 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
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
2
roughness as input to gradually-varied flow computations.
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 appro-
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
,
3
D 1129 Terminology Relating to Water
FIG. 1 Definition Sketch of Step-Backwater Reach
D 2777 Practice for Determination of Precision and Bias of
3
Applicable Methods of Committee D-19 on Water
equal to unity if the cross section is not subdivided. For
D 3858 Practice for Open-Channel Flow Measurement of
subdivided sections, a is computed as follows:
3
Water by Velocity-Area Methods
3
k
i
(
3. Terminology
2
a
i
a5 (1)
3.1 Definitions: 3
K
T
3.1.1 For definitions of terms used in this test method, refer 2
A
T
to Terminology D 1129.
3.2 Definitions of Terms Specific to This Standard: where:
NOTE—Several of the following terms are illustrated in Fig. k and a 5 the conveyance and area of the subsection
indicated by the subscript i, and
1.
K and A 5 the conveyance and area of the total cross
3.2.1 alpha (a)—a dimensionless velocity-head coefficient
section indicated by the subscript T.
that represents the ratio of the true velocity head to the velocity
3.2.2 conveyance (K)—a measure of the carrying capacity
head computed on the basis of the mean velocity. It is assumed
of a channel without regard to slope and has dimensions of
cubic feet per second. Conveyance is computed as follows:
1
This test method is under the jurisdiction of ASTM Committee D-19 on Water
1.49
2/3
and is the direct responsibility of Subcommittee D19.07 on Sediments, Geomor-
K 5 AR (2)
n
phology, and Open-Channel Flow.
Current edition approved April 15, 1993. Published June 1993.
3.2.3 cross-section area (A)—the area at the water below
2
Barnes, H. H., Jr., “Roughness Characteristics of Natural Streams,” U.S.
the water-surface elevation that it computed. The area is
Geological Survey Water Supply Paper 1849, 1967.
3
Annual Book of ASTM Standards, Vol 11.01. computed as the summation of the products of mean depth
1

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D 5388
2 2
multiplied by the width between stations of the cross section.
A 5 cross-section area, ft (m ),
3.2.4 cross sections (numbered consecutively in downstream R 5 hydraulic radius, ft, (m), and
order)—representative of a reach and channel and are posi- S 5 friction slope, ft/ft (m/m).
f
tioned as nearly as possible at right angles to the direction of 3.2.11 roughness coeffıcient (n)—or Manning’s n is used in
flow. They must be defined by coordinates of horizontal the Manning equation. Roughness coefficient or Manning’s n is
distance and ground elevation. Sufficient ground points must a measure of the resistance to flow in a channel. The factors
be obtained so that straight-line connection of the coordinates that influence the magnitude of the resistance to flow include
will adequately describe the cross-section geometry. the character of the bed material, cross-section irregularities,
depth of flow, vegetation, and channel alignment. A reasonable
3.2.5 expansion or contraction loss (ho)—in the reach is
evaluation of the resistance to flow in a channel depends on the
computed by multiplying the change in velocity head through
experience of the person selecting the coefficient and reference
the reach by a coefficient. For an expanding reach:
to texts and reports that contain values for similar stream and
ho 5 Ke~h 2 h ! (3)
v v
1 2
flow conditions (see 10.3).
and for a contracting reach:
3.2.12 velocity head (h )—in ft(m), compute velocity head
v
as follows:
ho 5 Kc~h 2 h ! (4)
v v
...