Effects of Vegetation Morphology on Mean Velocity and Turbulence Intensity under Oscillatory Flows and Their Implications for Sediment Transport in Benthic Zone

Aquatic vegetation modifies the flow by generating coherent structures and imposing resistance. Flow-vegetation interaction becomes function of individual plant morphology (stem and leaf shape and dimensions), canopy density, and spatial distribution of vegetation. We investigate the effect of plant morphology on turbulence intensity under oscillatory flows. By using a state-of-the-art 3D volumetric Particle Image Velocimetry system (3D-PIV), we characterize the mean velocity and turbulence statistics near and around submerged vegetation within an oscillatory tunnel. The U-shape oscillatory tunnel allows us to reproduce well-defined waves over a wide range of periods and amplitudes, whereas the 3D-PIV system allows us to obtain instantaneous velocity fields with high temporal frequency and spatial resolution in the vicinity of several types of vegetation. Our study of the three-dimensional velocity field provides further insight into the near-bed flow conditions and its interactions with the observed leaf-, stem- and canopy-scale flow structures, which in turn control resuspension and deposition of sediment within and around patches of vegetation. Since vegetation-induced turbulence drives essential transport mechanisms for ecosystem development, such as gas exchange, nutrient transport, bed and suspended sediment transport, among others, characterization of its dependence on plant morphology and flow conditions will improve our understanding of their role in aquatic environments and the impacts caused by human activities on coastal and tidal vegetated areas.