Author(s): P. M. Mckee; E. M Elsawy; E. J Mckeogh
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Abstract: The hydraulic characteristics of flow in a compound channel of a deep main channel and one flood-plain, were investigated in the laboratory. The main channel to flood-plain width ratio and flow depth were varied while maintaining constant bed slope. Velocity and turbulence distributions were measured by Laser-Doppler. Anemometry technique and shear stress distribution were measured using a Preston tube. Results confirmed that when over bank flow occurs in a river velocities and discharges in the compound channel are decreased by the interaction mechanism. Also energy, as quantified by an apparent shear stress at the interface, showed that main channel lost up to 25% of its energy while the flood-plain was increased by up to 250%. Shear stress ratios for non-interacting and interacting conditions were related to the geometry of the cross-section. By further analysis velocity and discharge ratios were correlated with shear stresses. Semi-empirical formulae were proposed and compared with the Manning equation to take into consideration the effect of interaction mechanism.
Year: 1985