Ecological impact assessment – dredging Porto Central
Porto Central is a private deep-water industrial port complex under development at the center of the Brazilian east coast in the State of Espírito Santo. The approximately 2,000 hectares deep-water port with up to 25 meters draft, is capable to receive deep-draught vessels, such as Valemax and VLCC’s – Very Large Crude Oil Carrier.
A 25-km approach channel should enable vessels to reach the port. Both the basin and the approach channel need to be dredged, resulting in a capital dredging volume of about 170 million m³. The dredging and offshore disposal will create high-turbidity plumes and additional sedimentation in an environmentally fragile coastal zone.
Royal HaskoningDHV is asked to define expected high-turbidity plumes and sedimentation values, and to assess the potential impact on the sensitive coastal environment.
Royal HaskoningDHV used sediment dispersion modelling to predict the spreading of sediment brought into suspension during the dredging and offshore disposal activities. Among others, an assessment of the dredging approach was made, including the effect of overflow. Numerical modelling software MIKE21 FM has been used, which accounts for tidal currents, ocean currents, wind-generated currents, and waves. The model results were used for the assessment of environmental impact, in particular on the rhodolite corals.
Royal HaskoningDHV developed an Adaptive Dredging Scheme based on the model results in combination with threshold sediment concentrations and deposition rates. This Adaptive Dredging Scheme enabling for quick adjustment of the dredging method to prevent negative impact on the coastal environment.
The study gave valuable insight in the environmental impact that can be expected during and after dredging the port basin and approach channel. Applying Adaptative Dredging enables the prevention of avoidable negative environmental impacts along the Brazilian coast caused by the dredging and disposal activities.