Based on Acoustic Doppler Velocity Profiler (ADVP) field measurements, we discuss ve-locity profiles observed in two shallow gravel-bed rivers with low relative submergence. Inthese flows, log-shaped profiles and s-shaped profiles simultaneously exist, indicating thepossibility of 3D flow inside the roughness layer. A quasi-2D layer is generally found in anintermediate region of the flow above the roughness layer. Therefore a best-fit log-law ap-proach may lead to estimates of a roughness parameter which are reasonably correlated withthe local flow resistance. However, above a certain limit of the ratio roughness/water depth(≈0.6 from our measurements), the velocity distribution in the lower regions predominantlycorresponds to an s-shaped profile.
|Journal||Archives of Hydro-Engineering and Environmental Mechanics|
|Publication status||Published - 1 Jan 2009|