Influence of emergent and submerged plants on local hydrodynamics and turbulence anisotropy in vegetated rivers

This study investigates the influence of three plants configurations – Full emergent Vegetation (FV), Central Cut (CC), and Extensive Cut (EC) – on the hydrodynamics and turbulence anisotropy within a reclamation channel colonized by rigid Phragmites australis plants. Turbulence anisotropy is quantified via both turbulence intensities and anisotropy invariant map (AIM) derived from the Reynolds stress deviatoric tensor. Results demonstrate that FV setup induces the highest anisotropy, characterized by a quasi-two-component (disk-like) turbulence regime due to enhanced horizontal fluctuations. Conversely, EC and CC configurations promote vertical fluctuations and near-bed oblate (disk-like, from three- to two-component) turbulence with transition to prolate (rod-like, from three- to one-component) anisotropy tendencies near the free surface. In the CC configuration, the side emergent uncut plants stands foster lateral velocity gradients and transverse momentum exchange. These results demonstrate how plants spatial distribution and submergence modulate local turbulence anisotropy and hydrodynamics governing vegetated watercourses.