Author(s): Hariom Gautam; Anirban Mandal; Zulfequar Ahmad; Pramod K. Sharma

Linked Author(s): HARIOM GAUTAM

Keywords: Velocity Distribution; Local Scour; Individual Flexible vegetation; Turbulence

Abstract: Vegetation in waterways alters flow by modifying velocity distributions, inducing turbulence, and increasing resistance, leading to bedform development such as scour and sediment deposition. The present laboratory study investigates the effects of individual submerged flexible vegetation on turbulent flow and sedimentation patterns, including scour and deposition. An artificial flexible plant made of plastic with an irregular shape and non-uniform frontal width was used to replicate natural sedge/grass. The experiments were conducted under different flow conditions for both vegetated and non-vegetated scenarios. Velocity profiles and turbulence characteristics were measured using an Acoustic Doppler Velocimeter (ADV), while scour and deposition patterns were recorded via an ultrasonic bed profiler. Results indicate that submerged vegetation significantly modifies bed morphology by enhancing wake turbulence and altering velocity distribution. Scour depth and sediment transport increased with discharge, with maximum scour occurring at the plant root zone due to intensified shear stress and vortex-induced turbulence. Downstream deposition shifted with higher discharge as reduced flow velocity facilitated sediment settling. Vorticity analysis revealed turbulence intensification near the canopy top due to shear-layer instabilities, promoting sediment resuspension. Drag coefficient analysis highlighted the role of plant flexibility in increasing wake turbulence and momentum loss. Velocity vector analysis showed reduced near-bed velocities and upward flow redirection, stabilizing the channel bed while enhancing sediment transport. The ratio of mixing layer to momentum thickness differs between a single plant and fully developed vegetated flow.

DOI: https://doi.org/10.64697/978-90-835589-7-4_41WC-P2123-cd

Year: 2025