Flow‐Measurement Structures of Compound Cross Section for Rivers

Abstract

Several types of flow‐measurement structures are used in rivers. One of the more common flow‐measurement structures is the critical‐depth flume. By definition, the velocity increases through the contracted section of the flume, which, in turn, minimizes deposition of sediment in the structure. Critical‐depth flumes are preferred in rivers where sediment transport through the structure is substantial. Dimensioning of these flumes for sediment‐free flow conditions over the structure has not yet been studied. In this paper, theoretical and experimental studies carried out on critical‐depth flumes of symmetrical compound cross sections are presented. Design criteria based on hydraulic model studies conducted with sedimentary materials having various properties are given. Following the procedure for dimensioning a proper flow‐measurement structure, a design example is presented for application. This procedure can easily be applied to a river of known hydraulic and geometric properties to determine the appropriate dimensions of the flow‐measurement structure along which there will be no sediment deposition under any flow condition. Consequently, a fixed rating curve that is unaffected by sediment deposition can be obtained for the flow‐measurement structure.