Prediction of plume generation and movement from dredging operations in Port Phillip Bay, Melbourne

This paper describes the calibration, validation and application of numerical models to assess the spreading, dispersion and settling of the material put into suspension by dredging operations in Port Phillip Bay. The models were set-up and validated using the field data collected during a trial dredging program specifically undertaken as part of investigations for the Supplementary Environment Effects Statement. A brief discussion of the trial and some of the data collected is included. A range of dredging scenarios consisting of varying wind and tide conditions and different dredging configurations were simulated. The full dredging program, spanning about two years, was modelled and, in addition, more than one operational scenario was considered so that a very large modelling effort was undertaken. The results show that the plumes in the south of Port Phillip Bay are driven primarily by the strong tidal-currents and can travel relatively large distances with varying levels of turbidity. In the north of the Bay, the tidal flows are much less and the turbid plumes do not travel large distances from the area of dredging operations. The time-series of turbidity at ecologically sensitive locations in combination with statistical patterns derived for the entire model area provide an estimation of both spatial and temporal variation of turbidity.