CONICET | Buscador de Institutos y Recursos Humanos

Measurements of flow, suspended matter transport and maximum distance travelled by the tidal front in a coastal plainestuary, located in the southeast of Buenos Aires province (Argentina) are reported. The system has shallow upper andmiddle sectors, while an important deep-water port is installed along the lower zone. Findings are related to themorphology, river discharge, tidal height and meteorological conditions. Salinity profiles, velocity field and backscatterintensity were obtained during tidal cycles in stations located in the last 10.5km of the estuary. The concentration, type andsize of the suspended elements are determined analysing water samples, and generalized for the cross-section by meansof the relationship between the backscatter intensities of two ADCPs operating at different frequencies. Under calmweather conditions, the estuary is stratified and the suspended solids consist mainly in flocs of varied sizes composed ofparticles of medium and very fine silt, clay and abundant organic matter. Hence, the stratified estuary behaves as a lowenergy system that favours the aggregation of the wash load while the settling of sediments occurs mainly on specificplaces of the harbour where intense dredging is needed. The results are the first of a series of long-term measurementsunder different hydrodynamic conditions and complement those previously obtained in the lower sector, thus contributingto the understanding of the global estuarine dynamics. The information acquired compensates for the lack of systematicmeasurements due to the wide range of river flow and the morphological and structural changes that occurred in the portzone, mainly in the last decades.