Monitoring outcomes supporting maintenance dredging and ocean disposal at Rosslyn Bay Boat Harbour

The Department of Transport and Main Roads (TMR) manages Rosslyn Bay Boat Harbour, located south of Yeppoon in Central Queensland. Due to its location 40km north of the Fitzroy River entrance, the harbour experiences significant siltation and requires frequent (3-4 yearly) maintenance dredging. To support the maintenance dredging campaigns over the last eight years TMR has undertaken a range of modelling and monitoring investigations. This paper discusses the project learnings from these investigations, with a particular focus on the environmental monitoring methodologies, the monitoring outcomes and how these outcomes will be used to refine future monitoring strategies for this site. The Water Quality data collected shows that wind, wave and freshwater flooding events during the dredging project caused high turbidity and low light conditions at the sensitive sites monitored and at the control site 10km south. For this reason no impacts could be attributed to the dredging project itself. Hydrographic Monitoring indicated that 75% of the material placed at the disposal site had been re-suspended and redistributed during the works. As of the time of writing the benthic surveys were not complete however these results post dredge and then 12 months after the works will be important in guiding ongoing management of Rosslyn Bay Boat Harbour.