Application of the entropy model to estimate flow discharge and bed load transport in a large river

The amount of sediment bed load being carried by rivers significantly impacts the inherent development of the riverine systems in terms of hydrodynamic and morphodynamic changes. In this direction, acoustic Doppler current profiler velocity literature data collected at the Óbidos station in the Amazon River were applied to investigate bed-load transport using the Entropy method. First, the cross-sectional velocity distribution was estimated with that model for two scenarios of source data: (a) all surface velocities and (b) single surface velocity as the maximum surface velocity. The latter analysis was conducted with two different assumptions of the surface velocity distribution: parabolic and elliptic. The error percentage for estimation of the mean cross-sectional velocity and discharge was 2.08% based on considering all surface velocities and was 4.08% and 12.5% based on parabolic and elliptic scenarios, respectively. Next, the shear velocity and Shields mobility parameter were calculated for two scenarios. Finally, the dimensionless bed load transport rate was calculated based on a range of particle diameters. Applying the different equations for the dimensionless bed load transport rate based on various scenarios of surface velocity distributions, the results from the entropy method agreed with the experimental data in the literature. Overall, the current study highlighted the potential of the entropy model to estimate river discharge and bed load transport in large rivers relying only on surface velocity.