Hydrodynamics and particulate suspended matter transport in a shallow and highly urbanized estuary: the Cocó estuary, Fortaleza, Brazil

Abstract

This study evaluates the hydrodynamics of the Coc´o river estuary (Fortaleza, Cear´a State, Brazil). Two 25-hour campaigns were carried out in different tide conditions during summer. Water level variation and current speed and direction data were acquired using an Acoustic Doppler Current Profiler (ADCP). Surface and bottom salinity and temperature data were collected using a Conductivity and Temperature (CT). Samples of surface and bottom water were collected every hour in order to determine Suspended Particulate Matter (SPM). The salinity and temperature vertical profiles showed an homogeneous behavior during most of the time in both campaigns, although during neap tide, small differences were observed due to low tidal range and consequent lower mix present in the Coc´o river. The SPM concentration variation presented a direct correlation with tidal waves, increasing at the surface and at the bottom during floods and then decreasing during ebb tide. The Coc´o river estuary is an importer of SPM during spring and neap tidal conditions, with larger negative transport during neap tides. Furthermore, the estuary presented as highly turbulent in both tidal conditions, although during neap tide the stratification overcame the turbulence in some situations.