Dinâmica da pluma de sedimentos oriundos de atividades de dragagens no estuário da Beira - Moçambique

Abstract

The Beira Estuary in Mozambique is a marine system of high importance in terms of biodiversity, and navigation use at Beira Harbor , the second largest harbor of Mozambique. The intense traffic of large ships implies frequent activities of maintenance of the port access channel, since it suffers severe siltation. Dredging activities have negative impacts on the marine environment, and may temporarily affect the abundance and distribution of marine species, also causing change in estuarine circulation and its bathymetry. This paper focuses on the evaluation of sediment plume dispersion from dredging activities in the Beira Estuary, and was based on hydrodynamic and sedimentological modeling using Delft3D software. In general, tidal currents are responsible for sediment transport within the estuary, and dredging activities increase the concentration of suspended sediments (near the surface) and near the bottom during their execution. River discharges have an important influence limited to their mouths, transporting sediments towards the estuary. The wind action induces currents with variable directions in the shallower areas, conditioned by bathymetry (channels and sandbanks) also being responsible for sediments transport. The dynamics of the dredging plume is mainly conditioned by the hydrodynamics that depends on the bathymetry characteristics and the tidal action.