Author(s): Mehdi Yasi
Linked Author(s): Mehdi Yasi
Keywords: Mean velocity; Relative submergence; Coarse-bed rivers
Abstract: The main characteristic of the flow in coarse-bed rivers is the development of an armor layer with cobbles and boulders. While this layer establishes a stable and smooth boundary at low flows, its mobility introduces a different mode of bed-roughness configuration during high flows. The process of flow resistance is complex for this type of rivers, and data are limited for a range of unsteady flows. Reliable prediction of mean velocity in such rivers is of major importance in river engineering. Several relationships have been presented and tested against data in gravel-bed rivers and mountain streams. The application of such equations has not been fully evaluated in coarse gravel, cobble and boulder-bed rivers under different flow conditions. The present study was aimed at obtaining an accurate set of data in a typical reach of a coarse-bed river in Iran. The Fahlian River reach was selected to investigate the most hydraulic information, under different flow conditions during a flooding period. This paper compares the measured values of mean velocities with those predicted by some present relationships applicable to the study reach. The flow condition under which each of these equations is to be valid is determined by an error level of 10% and 30%. A purpose-developed equation has been presented to estimate the mean velocity in different reaches of the Fahlian River and in similar rivers by an error range of γ■10%.
Year: 2001