Sediment Exchange between a River and Its Groyne Fields: Mobile-Bed Experiment |
| |
Authors: | Mohamed F. M. Yossef Huib J. de Vriend |
| |
Affiliation: | 1Researcher/Consultant, Deltares (Delft Hydraulics), Delft, The Netherlands; formerly, Ph.D. Student, Section of Hydraulic Engineering, Delft Univ. of Technology, The Netherlands (corresponding author). E-mail: mohamed.yossef@deltares.nl 2Professor, Section of Hydraulic Engineering, Delft Univ. of Technology, The Netherlands.
|
| |
Abstract: | Experiments have been carried out in a mobile-bed laboratory flume in order to study the sediment exchange process between the main channel and the groyne fields. The flume represented half the width of a schematized river reach with a series of groynes. The experiment was designed to represent typical dimensions of the Dutch River Waal at a geometrical scale of 1:100. The conditions were set to guarantee bed load as well as suspended load sediment transport. Conditions with submerged and emerged groynes were investigated. In addition to traditional measurements, viz., bed-level changes, suspended sediment concentrations, and flow velocities, bed-form propagation was measured in two dimensions using a the particle image velocimetry technique. The results were analyzed with focus on sediment exchange mechanisms and sediment transport patterns. The results demonstrate that under all flow conditions there is a net import of sediment into the groyne fields. The prevailing transport mechanisms vary with the flow stage: if the groynes are emerged it is mainly advection by the primary circulation cell, whereas if the groynes are submerged it is rather residual advection by large-scale coherent flow structures (in a straight reach). Additional entrainment of sediment by enhanced turbulence complicates the erosion/deposition patterns. |
| |
Keywords: | Groins, structures Flumes Laboratory tests Scour Sediment transport Rivers Morphology Measurement |
|
|