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Designation: D5243 − 92 (Reapproved 2013)Standard Test Method forOpen-Channel Flow Measurement of Water Indirectly atCulverts 1This standard is issued under the f i xed designation D5243; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (´) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the computation of discharge(the volume rate of f l ow) of water in open channels or streamsusing culverts as metering devices. In general, this test methoddoes not apply to culverts with drop inlets, and applies only toa limited degree to culverts with tapered inlets. Informationrelated to this test method can be found in ISO 748 and ISO1070.1.2 This test method produces the discharge for a f l oodevent if high-water marks are used. However, a completestage-discharge relation may be obtained, either manually orby using a computer program, for a gauge located at theapproach section to a culvert.1.3 The values stated in inch-pound units are to be regardedas the standard. The SI units given in parentheses are forinformation only.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards: 2D1129 Terminology Relating to WaterD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3858 Test Method for Open-Channel Flow Measurementof Water by Velocity-Area Method2.2 ISO Standards: 3ISO 748 Liquid Flow Measurements in Open Channels-Velocity-Area MethodsISO 1070 Liquid Flow Measurements in Open Channels-Slope-Area Methods3. Terminology3.1 Def i nitions—For def i nitions of terms used in this testmethod, refer to Terminology D1129.3.2 Several of the following terms are illustrated in Fig. 1.3.3 Def i nitions of Terms Specif i c to This Standard:3.3.1 alpha (α)—a velocity-head coefficient that adjusts thevelocity head computed on basis of the mean velocity to thetrue velocity head. It is assumed equal to 1.0 if the cross sectionis not subdivided.3.3.2 conveyance (K)—a measure of the carrying capacity ofa channel and having dimensions of cubic feet per second.3.3.2.1 Discussion—Conveyance is computed as follows:K 51.486nR2/3 Awhere:n = the Manning roughness coefficient,A = the cross section area, in ft 2 (m 2 ), andR = the hydraulic radius, in ft (m).3.3.3 cross sections (numbered consecutively in down-stream order):3.3.3.1 The approach section, Section 1, is located oneculvert width upstream from the culvert entrance.3.3.3.2 Cross Sections 2 and 3 are located at the culvertentrance and the culvert outlet, respectively.3.3.3.3 Subscripts are used with symbols that representcross sectional properties to indicate the section to which theproperty applies. For example, A 1 is the area of Section 1.1 This test method is under the jurisdiction of ASTM Committee D19 onWaterand is the direct responsibility of Subcommittee D19.07 on Sediments,Geomorphology, and Open-Channel Flow.Current edition approved Jan. 1, 2013. Published January 2013. Originallyapproved in 1992. Last previous edition approved in 2007 as D5243 – 92 (2007).DOI: 10.1520/D5243-92R13.2 For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at service@astm.org. For Annual Book of ASTMStandards volume information, refer to the standard’s Document Summary page onthe ASTM website.3 Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http://www.ansi.org.Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1