Sea bottom characteristics related to tidal currents at Rosales Port, Bahía Blanca Estuary, Argentina.

SILVIA SUSANA GINSBERG; DIANA G. CUADRADO; EDUARDO A. GÓMEZ

Mar del Plata, Pcia de Bs As

Simposio; Joint IAPSO-IABO Assembly 2001: An Ocean Odyssey. Symposium IB01: Regional estuarine and coastal systems of the Americas.; 2001

Rosales Harbour was constructed on the northern coast of Bahía Blanca Estuary (Argentina), to provide shipping services for fisher-ship. North-south stone pier interrupt the sediment transport towards the southeaster-northwester arises different zones at both sides it. Therefore, eastward the pier is located an ancient and wide tidal flat, which is exposed during low tide and westwards the pier a deeper area is found. The differences between both sides continue at the subtidal area, where eastwards sector is covered by asymmetrical megaripples that abruptly end close to the pier, giving place to bottom composed by consolidated. Internal estuarine processes and southern storms simultaneously affect these areas. As a consequence these processes have increased the sedimentation rates more than expected. Bathymetric surveys, side scan sonar sonograms, grain size trends of surficial sediment and currentmeters data were used to define the dynamics of both sector. Observation of the morphologies of the west and east pier in relation to currents behaviour and sediment transport show that the above relations difference in the harbour morphologies is due to the pier induced longshore drift for the different sectors. Computations of sediment transport as bed-load also show differences between both areas. This preliminary evidence suggests that subtidal and intertidal differences between both areas may be related to an acceleration of tidal currents caused by the presence of the pier.