Influence of Flow and Sediment Transport Processes on the Sedimentation in Groyne Fields

Groynes have been widely used to maintain a suitable channel for the purpose of flood control, bank protection and to improve navigation conditions. Various deposition patterns have been found in the groyne fields which are supposed to relate to the flow and sediment transport processes. For a groyne field dominated by a single large gyre and the sediment being mainly transported in form of suspended load, the sediment deposition pattern is found to be consistent with the gyre structure. For groyne fields showing complex flow structures or bedload dominating the sediment transport process, the relationship between the deposition patterns and the flow and sediment transport processes is unclear yet. In this study, the deposition patterns of groyne fields formed by different flow and sediment transport processes were analyzed based on flume experiments. The topographic change in groyne fields was measured using a high-precision photogrammetric method. The bedload transport process near the groyne fields was captured by analyzing time-sequential photos of the flume bed using a spatial-correlation method. The distribution of flow characteristics was calculated using the Horizontal Large Eddy Simulation (HLES) of the Delft3d model. The results confirmed that the deposition patterns were affected by the flow structures and sediment transport processes. For suspended sediment dominated situations, the deposition patterns were consistent with the gyre structures. For bedload dominated conditions, the sediment deposition occurred where the bed shear stress falls below the critical shear stress.