SUSPENDED SEDIMENT TRANSPORT IN A HIGHLY STRATIFIED ESTUARY UNDER TRANSIENT RIVER DISCHARGE

Abstract

The present paper assesses the hydrodynamics and suspended sediment transport in the Araranguá river estuary in response to a flood peak. A field survey was carried out in May, 2006, when water level, current velocity and direction, salinity and suspended sediment concentration (SSC) were recorded. Current data were obtained through a moored acoustic Doppler current profiler, from which the SSC were estimated based on the acoustic backscattering. The field survey was carried out just after a flood 3 -1 peak, during the waning phase of the hydrogram, when the discharge decreased from 120 to 30 m s in a 50-hour period. The longitudinal salinity distribution was strongly affected as well as the currents and SSC. The currents responded to the flood peak by changing from a barotropic regime downstream to a two layer baroclinic, with downstream currents at surface layer and upstream currents at the bottom layer. The suspended sediment transport was directly related to the currents, changing from an exportation phase during the flood peak to an importation phase through the bottom layer.