A depth‐averaged two‐dimensional model for flow, sediment transport, and bed topography in curved channels with riparian vegetation

Abstract

A depth‐averaged two‐dimensional numerical model has been developed to simulate flow, sediment transport, and bed topography in river channels with emergent and submerged rigid vegetation and large woody debris. The effect of helical flow in bends is considered by adopting an algebraic model for the dispersion terms in the depth‐averaged two‐dimensional momentum and suspended‐sediment transport equations and by adjusting the bed load transport angle. The governing equations are discretized using the finite volume method on a nonstaggered, curvilinear grid. Model validity has been assessed using experimental data observed in both fixed‐ and movable‐bed laboratory flumes and a natural channel with submerged and emergent rigid vegetation. In general, mean flow velocities, sediment transport rates, and changes in bed topography predicted by the model agree well with the experimental observations. For laboratory and field cases, root‐mean‐square relative errors for velocities were less than about 13% and 44%, respectively, and about 50% of errors for changes in bed topography were less than 14.5% and 8% of the flow depth, respectively.