Abstract

The silting of fine suspended sediments in shallow reservoirs is a phenomenon which is not yet fully understood. It involves complex physical processes such as transport of bed and suspended load, deposition, as well as erosion or resuspension. This paper presents the influence of the width of rectangular shallow reservoir on the sediment depositions and flow patterns. The experimental study focuses on the sedimentation of shallow reservoirs mainly by suspended sediments. The water surface elevation in the reservoir is similar for all experiments. Water and sediment discharge conditions remain constant during the experimental runs. This allows to understand the complex relation between flow patterns, sediments exchange and sediments transport. In spite of the symmetric setup, an asymmetric flow and sediments pattern developed. For all tested geometries, the influence of suspended sediments on both flow patterns and bed forms was found very similar. At the beginning of the tests, the highest sediments depositions and concentrations were found along the main jet flow, where the velocity is highest. The flow pattern was stable, with smooth or relatively low roughness over the entire bed. However, after some time, ripples developed underneath the main jet, with thicknesses of about 0.15 times the flow depth. These were able to change the flow pattern.

Keywords: Flow patterns, Sedimentation of shallow reservoirs; Suspended load; Sediments retention basin; Rectangular reservoir geometry