Flexible vegetation distributed on the bed of the apex section of a meandering bend: an experimental study on the effect on the lateral dispersion

Understanding flow characteristics and dispersion processes in rivers in the presence of vegetation is especially important with respect to the identification of the water quality and the ecosystem conditions. In the present paper attention is focused on the lateral dispersion processes in a high‐curved channel with different distributions of flexible submerged vegetation on the bed. The analysis is conducted with the aid of data collected in a large amplitude meandering channel constructed at the Department of Engineering – University of Palermo. In particular, the study examines the lateral dispersion coefficient at the apex section of the flume in three different conditions of the bed: in the absence of vegetation, in the presence of uniformly distributed flexible vegetation, in the presence of two squared patches of flexible vegetation. Results show that the presence of vegetation affects the distribution of the lateral dispersion coefficient. In particular, while in the absence of vegetation the lateral diffusion could play an important role in the central part of the water depth, in the presence of uniformly distributed vegetation it could be important just close to the top of vegetation depending on the value of relative submergence. In the case of partially distributed vegetation a behavior similar to that obtained in the case of uniformly distributed vegetation has been observed in the vegetated patches, but in the transition from the non‐vegetated areas to the vegetated ones the fluctuation of the vegetated stems still affects the values of the lateral dispersion.