A sediment fluxes investigation for the 2-D modelling of large river morphodynamics

• We investigated sediment fluxes in a bifurcation of the large Parana River.
• A 2-D numerical un-coupled model was applied to the bifurcation reach.
• Numerical experiments were performed to test the model reliability.
• The grid longitudinal spacing corresponded to the wave length of the observed dunes.
• The morphodynamic time step accounted for the observed river bars celerity.

A complete understanding of alluvial-bed dynamics is desirable for evaluating a variety of issues related to water resources.Sediment fluxes were investigated in a bifurcation of the large Parana River near Rosario, Argentina. The backscatter estimations from the Doppler profilers provided the suspended load of the sediment forming the riverbed. An echo-sounder was applied to track the dunes yielding the bed-load estimation.Aiming to show the usefulness of the recorded data, a 2-D numerical code was applied to the 10-km long and 2-km wide Rosario reach. The morphodynamic module was un-coupled from the hydrodynamics assessment, which enabled the long-term prediction of the river morphology accounting for the hydrological yearly variation with a quasi-steady approach.Numerical experiments were performed to test the sensitivity of the hydrodynamic model to the computational time-step and mesh size, to test the un-coupling scheme performance regarding the full-dynamic modelling, to test the accuracy of the sediment transport formulae based on the field evidence and, finally, to provide guidance to properly fix the model parameters.