Circulation and suspended sediment transport in a sediment starving ria: the Itapessoca

Abstract

The Itapessoca estuary is part of the Itamaracá-Itapessoca Estuarine System, a ria-type estuary located on the northeast Brazilian shore, in the state of Pernambuco. Here we present an assessment of the estuarine circulation, suspended sediment dynamics, and its main transport mechanisms. We carried out a field survey where water level, currents, salinity, temperature, and suspended sediment concentration (SSC) were recorded at 10-minute intervals during two complete semi-diurnal tidal cycles under spring tide conditions. The field survey was conducted in September (2012), which is a transitional period between wet and dry seasons. The water level displayed symmetrical ebb-flood phases; however, currents were ebb-dominated. The freshwater contribution was negligible, and the mean salinity was ~35 g/kg, which is slightly lower than the adjacent shelf values (36.5 g/kg). The SSC transport was driven by the ebb-dominated tidal currents, with the highest values of ~30 mg/l occurring during the peak current during the ebb. The source of the suspended sediment was the erosion from the bottom, and the concentration was much lower than other similar estuaries (e.g., Caravelas). This observation suggests this system is a ‘sediment starved system’ in the sense that it presents a low concentration of suspended sediment.