Modeling the Suspended Sediment Transport in a Very Wide, Shallow, and Microtidal Estuary, the Río de la Plata, Argentina

The impact of the diverse processes responsible for the distribution of suspended sediments in the wide, shallow, and microtidal Río de la Plata estuary and the adjacent shelf is studied by means of a set of process-oriented numerical simulations. Model results show that the large width and the geometry of the estuary play a major role in the sedimentation processes. The widening and deepening of the estuary drives a significant reduction in current speeds at (i) the confluence of the tributaries and (ii) downstream Barra del Indio Shoal. Thus, sediment deposition enhances downstream those areas. Even though tides are of small amplitude in the study area, they have a significant impact on lateral mixing and resuspension of the bottom sediments. Resuspension augments the concentration of fine sediments in the layers close to the bottom, but tidal energy is not enough to lift them to the surface. Winds (which can be quite strong over this area) enhance horizontal mixing, smoothing the pattern produced by tides. Wind waves increase the concentration of sediment by vertical mixing, and their effect is most evident along the southern coast where wind waves lift the sediments resuspended by tides to the surface. The estuarine circulations associated to the bottom salinity front acts retaining sediments upstream the Barra del Indio Shoal, where estuarine currents and flocculation play an important role in sediment deposition.Fil: Moreira, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; Argentina. Instituto Franco-argentino sobre Estudios del Clima y sus Impactos; ArgentinaFil: Simionato, Claudia Gloria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; Argentina. Instituto Franco-argentino sobre Estudios del Clima y sus Impactos; Argentin

Horizontal transport, mixing and retention in a large, shallow estuary: Río de la Plata

© 2014, Springer Science+Business Media Dordrecht. We use field data and a high-resolution three-dimensional (3D) hydrodynamic numerical model to investigate the horizontal transport and dispersion characteristics in the upper reaches of the shallow Río de la Plata estuary, located between the Argentinean and Uruguayan coasts, with the objective of relating the mixing characteristics to the likelihood of algal bloom formation. The 3D hydrodynamic model was validated with an extensive field experiment including both, synoptic profiling and in situ data, and then used to quantify the geographic variability of the local residence time and rate of dispersion. We show that during a high inflow regime, the aquatic environment near the Uruguayan coast, stretching almost to the middle of the estuary, had short residence time and horizontal dispersion coefficient of around 77 (formula presented.), compared to the conditions along the Argentinean coastal regime where the residence time was much longer and the dispersion coefficient (40 (formula pr esented.)) much smaller, making the Argentinian coastal margin more susceptible for algae blooms