The influence of dredging on estuarine hydrodynamics: Historical evolution of the Santos estuarine system, Brazil

We assess changes in estuarine hydrodynamics due to the deepening of navigation channels by dredging. A validated numerical hydrodynamic model (Delft3D) was used to analyze scenarios (historical bathymetry data from 1876 to 2014) and applied to assess the hydrodynamic evolution of the Santos estuarine system (SES), Brazil. During the studied period, the SES underwent significant morphological changes, mainly related to the dredging of the Santos harbor navigation channel. The unprecedented results of the hydrodynamic evolution of the SES show that the gradual process of deepening the channels by dredging resulted in modified estuarine circulation parameters such as tidal propagation and stratification of the water column, as well as the residual water and materials transport through the SES channels. Channel deepening resulted in greater saline intrusion, a decrease in the volume of water transported through the Santos channel, an increase in the influence of the tide in the system and an increase in its asymmetry over the years in the upper estuary. •We assess changes in estuarine circulation by the deepening of channels through dredging.•A validated hydrodynamic model (Delft3D) was used to analyze morphological scenarios.•Gradual deepening of the channels resulted in local changes in estuarine circulation.•Tidal propagation and water column stratification are modified.•Residual water transport through the estuarine channels is changed.