Vertically-averaged and moment model for meandering river morphology

Abstract

We report the first numerical tests of the two-dimensional vertically-averaged and moment (VAM) equations to simulate scour and deposition along alluvial meandering rivers with fixed banks. The VAM hydrodynamic model assumes a linear vertical distribution of the velocity profile and provides estimates of the magnitude and direction of the both near-bed and surface velocity vectors in a quasi three-dimensional (3D) fashion, reproducing at a very basic level some of the 3D effects of the secondary flow in bends. By assuming that the bed shear stress direction along the bed was given by the VAM’s near-bed velocity direction, it was possible to successfully reproduce the scour and deposition observed in a curved experimental flume and a meandering river reach. Although the VAM model is more general and does not require a secondary flow correction, as needed by conventional depth-averaged models, the results were not significantly better for the two cases analyzed.