A posible solution to Rosales Harbour excessive Siltation Rate (Bahia Blanca Estuary, Argentina)

Abstract

Puerto Rosales is the most external port in the Bahía Blanca harbour system, but it could never be fully developed as other ports of the system because an abnormally high siltation rate. Trying to diminish the harbour sediment income but not based on previous studies, in 1995 some modifications were introduced into the environment, increasing the siltation rate by about 600%. Suspended sediment concentration (SSC) profiles carried out through different wind conditions indicated that the source for the excessive SSC is the erosion of the neighboring tidal flats by locally generated waves. Also locally generated waves are responsible for an inward estuary littoral drift of sand about 4 m depth, exceeding the opposite net sediment transport rate caused by tidal currents. The more economically way to reduce the harbour excessive siltation rate would be to prevent the passage of water from where high SSC generates by constructing an eastward continuous barrier through the entire intertidal area. In order to avoid negative interactions between this barrier and tidal currents, a hydrodynamic mathematical model evaluated by field measurements is applied under different wind conditions. Three barrier lengths are tested, recognizing which one better behaves in order to prevent the passage of water from the intertidal areas and the growth of deposits of the sand transported by the littoral drift and/or the inward income of sand harbour by residual currents.