ABSTRACT
Groyne fields often provide favorable conditions for riparian and aquatic vegetation. Although hydrodynamics of flow in groyne fields is the subject of ongoing intensive research, effects of vegetation on the structure of recirculation flows in groyne fields is insufficiently understood. This paper reports preliminary results of a field experimental study, which examines hydrodynamics of flow in vegetated groyne fields. Field experiments were carried out in a branch of the Tagliamento River in Italy. Two sequences of 7 groynes each were constructed along the river banks. Eight experiments were carried out with model vegetation - wooden cylinders and flexible silicone model plants. Population density, submergence ratios, and patterns of vegetation were varied between the experiments. Measurements of flow were taken with an array of Vectrino++ velocimeters. The results indicate that presence of vegetation substantially rearranges the flow structure inside groyne fields. A twin circulation system, which is characteristic of the groyne fields with an aspect ratio of this study, was replaced by a return flow without notable recirculation, when the vegetation was rigid and emerged. The magnitude of the return flow was greatly reduced compared to the case without vegetation.
