An impact assessment of the planned deepening of the navigation channel of the entrance to Port of Santos, Brazil has addressed three main issues:

• Discharges in the water and lagoon system, water levels, currents and distribution of channel flow
• Intrusion of a salt water wedge and associated stratification
• Impact on sedimentation patterns and the general sediment balance due to deepening

The aquatic system in Port of Santos is influenced by three entrances to the port allowing seawater to enter the estuary such that a permanent stratification prevails yet with many smaller inflows feeding freshwater into the estuary. The area is characterized by its large mudflats and narrow channels surrounded by mangroves. The sediments change gradually from sand to clay when moving away from the sea - yet the composition of clay in the inner parts indicates both a marine as well as and a riverine component.

Using a detailed 3D model covering the entire Santos Estuary the following conclusions were reached:

• There will be small changes in the in- and outgoing fluxes due to deepening, only
• Likewise, small changes in salinities due to deepening are to be expected
• The deepening will lead to a small decrease in sedimentation rates in the mangroves while
• The sedimentation rates will increase in the channels