Real-time monitoring of turbidity levels and water velocities during dredge spoil placement within Moreton Bay, Queensland, Australia

This study presents a real-time monitoring and turbid event analysis approach within a dredge placement area located close to the Port of Brisbane, Moreton Bay, Australia. Turbidity and water velocities were measured continuously for the period spanning July 2018 - January 2019. Measured data was accessible to all parties involved including; dredge and port operators, environmental permit holders and research groups. Damaged or fouled instruments were identified remotely, resulting in approximately 14-days of unsatisfactory data for both bottom and surface turbidity parameters throughout the monitoring period. Median turbidity values prior to and during dredge operations were 2 NTU and 7 NTU respectively, values consistent with suspended sediment concentrations less than 10 mgL. The application of an event-by-event analysis approach identified 108 turbid events exceeding a pre-defined turbidity threshold (6 NTU). The applicability of the applied monitoring and analysis approach provides dredge operators in the area the potential for better decision making and the establishment of new monitoring guidelines for future dredge campaigns.