Flow characteristics in gravel bed rivers: an experimental investigation

The characterization of the kinematic characteristics of flow in gravel-bed rivers is one of the most important problems. In the present paper the streamwise velocity and turbulence intensity profiles are investigated on the basis of data collected in a straight laboratory gravel-bed flume. In order to take into account spatial heterogeneities, the double-averaged velocities are considered for the anal-ysis. Results show that, because of the presence of gravels, all the streamwise velocity profiles show an inflection point. Thus, the experimental profiles can be interpreted by the mixing layer scheme and considered as a composition of two parts of constant velocity separated by a confined interme-diate region (mixing layer) containing the inflection point. The thickness of the mixing layer varies passing from the banks to the channel axis.