CSIRO has released a new guideline that provides current best practice for dredge plume modelling in the context of Australia’s Environmental Impact Assessment processes.
The practical guideline aims to ensure that approaches taken in setting up and executing models are more consistent and improve confidence in decision making by environmental regulators that will also lead to reduced management costs for major dredging programs.
The Guideline on dredge plume modelling for environmental impact assessment takes into consideration the findings of five years of intensive studies through the Western Australian Marine Science Institution’s Dredging Science Node to help predict the intensity and extent of potential impacts on marine habitats from dredge-related pressures.
Lead author of the guideline CSIRO’s Dr Chaojiao Sun explained modelling dredge plumes is challenging and complex.
“Large-scale dredging campaigns that typically require the excavation of millions of tonnes of soil or rock material from the seabed are essential components of major port construction and deepening projects,” Dr Sun said.
“Dredging activities suspend sediment into the water and some of these sediments are then kept in suspension by coastal currents as they are carried downstream, resulting in horizontally spreading dredge plumes. The suspended sediment content in these plumes can reduce the amount of light reaching the seabed,” added Dr Sun.
“In areas where currents (bed stresses) are low, the plume sediments are no longer able to remain in suspension, and bed deposition occurs. These are two examples of dredging-induced environmental pressures that may induce potentially widespread ecological impacts in sensitive seabed marine communities including coral, seagrass and sponges,” Dr Sun stated.
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