Modelling vegetation effects in irregular meandering river

A numerical investigation of vegetation effects on the hydrodynamics of the Blackwater River, Hampshire, UK, is presented. The computational code Telemac-2D was applied to simulate a flood event in an irregular meandering reach. Velocities were measured at three cross-sections using Acoustic Doppler Current Profiler and Acoustic Doppler Velocimeter. With these, the friction factors for the main channel and the floodplain were calibrated. A uniform Manning coefficient method and an emergent vegetal drag force method to specify flow resistance of vegetation on the floodplain were used to compare flow simulations. An attempt was made to assess the accuracy of the constant viscosity model, the Elder model and the k-ϵ model. Simulated hydraulic parameters were used to assess the boundary shear stress. The vegetation greatly influenced flow behaviour, reducing both velocity and boundary shear stress as the drag force increases. These results can guide practising engineers in estimating flood conveyance and improve the understanding of bed shear behaviour in rivers with vegetated floodplains.