2003•Coasts & Ports 2003 Australasian Conference : Proceedings of the 16th Australasian Coastal and Ocean Engineering Conference, the 9th Australasian Port and Harbour Conference and the Annual New Zealand Coastal Society ConferenceRequires access
Reducing Dredging Costs for the Port of Townsville a Full Scale Hydrodynamic and Sediment Transport Model
Ross Fryar, Ivan Botev, Chris Martin, Chris J. Jones
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Abstract
The approach channel and a key berth in the outer harbour of the Port of Townsville have experienced heavy siltation since construction. This has required intensive maintenance dredging at a cost of about one million A$ per year. To cope with the problem, an investigation of several structural options designed to protect the berth has been initiated using a full-scale hydrodynamic and sediment transport modelling system. The model covers some 200 km of coastline and extends 50 km offshore. The modelling system has undergone extensive calibration to currents, waves and sediment transport data at both a regional and local scale. The hydrodynamic component of the system features three-level hydrodynamic nesting on a curvilinear grid and simulates the interaction of tidal currents with the predominant wave conditions. The results of modelling have illustrated the potential benefit of a new wall extending out to from the shore alongside the berth. The hydrodynamic model allows accurate simulation of sediment transport over the entire tidal cycle, capturing the re-suspension of sediment by different mechanisms. Wave action dominates during periods of neap tide with tidally induced transport occurring during spring tides. The simulation of the interaction between the tide and waves, and rigorous model validation, have proven to be the key factors in reproducing the monthly average deposition rates recorded in the area. Model calibration has been based on threshold bed-shear stresses, sedimentation/re-suspension fluxes and bi-modal grain size. A 'do nothing' option and three structural solutions have been compared based on the predicted volume of deposited suspended sediment in the berth. Creation of the model has led to several additional significant benefits. These revolve around the capability of the model to allow accurate impact assessments of future infrastructure and environmental assessments within the port area and surrounds. The model now allows the simulation of items or processes associated with navigability, a new marina, and oil spills.