Abstract This study experimentally investigates the hydrodynamic performance of submerged near‐bank rigid vegetation patches with varying densities in a channel containing submerged and emergent sandbars. The flume configuration naturally generated distinct low‐velocity and high‐velocity zones, enabling assessment of vegetation effects under contrasting hydraulic conditions. Flow measurements were obtained using an Acoustic Doppler Velocimeter (ADV) across six cross‐sections, focusing on non‐dimensional streamwise velocity (U*), turbulent kinetic energy (TKE*), Reynolds shear stress (RSS*), quadrant analysis, near‐bed shear velocity (u*) and shear layer characteristics. Results indicate that in low‐velocity zones (U* ≈ 2–4), sparse vegetation reduced velocity by 30–50%, while dense vegetation achieved marginal additional reductions. In high‐velocity zones (U* ≈ 8–10), sparse vegetation was largely ineffective, whereas dense vegetation reduced velocity by 30–35%. TKE* was reduced by 30–50% (sparse) and 40–60% (dense) in low‐velocity zones, compared to 40–60% (sparse) and 65–75% (dense) in high‐velocity zones. RSS* peaks were ~1.5 × higher in low‐velocity zones than in high‐velocity zones, with dense vegetation reducing RSS* by up to 65% in high‐velocity regions. Quadrant analysis showed a shift from sweep (Q4) dominance in non‐vegetated conditions to ejection (Q2) dominance with vegetation, particularly in dense configurations. Near‐bed u* was approximately twice as high in high‐velocity zones as in low‐velocity zones. Shear‐layer analysis showed that increasing near‐bank vegetation density extends the shear layer laterally and vertically in low‐velocity zones, and primarily vertically in high‐velocity zones. Overall, vegetation effectiveness is zone‐dependent, with moderate densities sufficient for low‐energy conditions and dense vegetation required in high‐energy zones.
Maurya et al. (Tue,) studied this question.