Possible sediment transport discharged from the Fitzroy River into estuary

The Fitzroy River is the largest river in Central Queensland discharging to the Central Queensland coast. The river flow is highly episodic and it periodically carries a very high sediment load which is transported into Keppel Bay and further on by coastal sediment transport processes. The high sediment load of the Fitzroy River is a major concern to both river and coastal waters due to the sediment quality. A report for the World Wide Fund (WWF) for Nature (Australia) states that the Fitzroy and Burdekin rivers contribute 19 million tons of sediment out of a total of 28 million tons dumped onto the reef each year. To verify those figures a proper sediment transport formula must be used for calculation. There are several available formulae, and the goal of the study presented in this paper was the adoption of one of them to Fitzroy River conditions, based on available field measurements. Comprehensive sediment sampling carried out by the Queensland Department of Natural Resources and Mines (DNRM) at the Laurel Banks site located about 76 km upstream of the Fitzroy River mouth during four flood events in the period 1994 -1999 allowed the evaluation of 14 different sediment transport formulae. Finally the authors have developed a sediment transport formula best suited to the Fitzroy River conditions. By applying acceptable formulae to hydro graph data for 35 years it was confirmed that approximately 20 million tons of sediment might be eroded from the catchment during the most severe flood events. The mean annual total sediment discharge has been computed to be more than 5 million tons, and the mean bed material discharge sums up to about 260,000 tons