Aspectos hidrodinâmicos do estuário do Rio Cocó, Fortaleza, Ceará, Brasil

Abstract

This study evaluates the hydrodynamics of the Cocó river estuary (Fortaleza, Ceará). Two 25-hour campaigns were carried out in different tide conditions during summer time. Water level variation and current speed and direction data were acquired using an Nortek Acoustic Doppler Current Profiler (ADCP). Surface and bottom salinity and temperature data were collected using an Nortek Conductivity and Temperature (CT). Surface and Bottom water were collected every hour in order to determine Suspended particulate matter (SPM). Based on the flood time, it was show that the flood current were more intense than the ebb, both during spring and neap tide. The salinity and temperature from surface to bottom showed an homogeneous behavior during most of the time in both campaigns, although during neap tide, small differences were recorded due to the low tidal range and consequent lower mix present on the Cocó river. The variation of the SPM concentration presented a direct correlation with the tidal waves, increasing at the surface and the bottom during floods and then decreasing during ebb tide. The dataset has been used to estimate the transport of particulate material, the Richardson number and the dimensionless circulation parameters to construct the Hansen & Rattray (1966) diagram. These results show that the Cocó river estuary is an importer of SPM in spring and neap tidal conditions, with larger negative transport in neap tides. Furthermore, the estuary behaved as highly turbulent in both tidal conditions, although during neap tide the stratification overcame the turbulence in few situations. The Cocó river estuary was classified as type 1a or vertically homogeneous.