2024 schedule for maintenance dredging of Queensland ports

This schedule has been prepared by the Queensland Ports Association as part of reporting requirements under the Queensland Government's Maintenance Dredging Strategy for Great Barrier Reef World Heritage Area Ports.

Queensland ports require routine maintenance dredging to remove sediments that have accumulated in channels, berths and swing basins due to siltation and sediment transport processes. Most ports cannot sustainably function without maintenance dredging. Maintenance dredging has occurred in Queensland since ports were first established. 

Most maintenance dredging is carried out by the Trailing Suction Hopper Dredge Brisbane which undertakes an annual dredging program of Queensland ports over a period of 6–8 months. The dredge, based in Brisbane and operated by the Port of Brisbane Pty Ltd, was specifically designed and built for Queensland conditions with the vessel applying high standards of environmental management. The environmental management mechanisms are equivalent to the features installed in the latest Trailing Suction Hopper Dredge models used around the world and ensure environmental impact is minimised during the dredging works.  

The Queensland Government has developed the Maintenance Dredging Strategy for Great Barrier Reef World Heritage Area Ports (the Strategy) consistent with the requirements of the Reef 2050 Long-Term Sustainability Plan. The Strategy aims to build on the current strong regulatory requirements and ensure the ongoing protection of the Reef’s values and the continued operating efficiency of ports within the Great Barrier Reef World Heritage Area.

The Strategy requires ports to work together to ensure that the annual state-wide maintenance dredging program for the Brisbane is developed to optimise environmental outcomes and operational efficiencies and to make the schedule publicly available.

The Strategy focusses on ports within the Great Barrier Reef World Heritage Area however, development of the state-wide schedule needs to consider other Queensland ports (for example Weipa, Amrun, Karumba and Bundaberg) as they also have maintenance dredging requirements and need to be included in scheduling of the Brisbane. The northern ports campaign can be influenced significantly by the level of monsoon activity or wet season extreme weather events, particularly at Weipa, or Karumba, and hence affect the schedule at the Great Barrier Reef ports. 

The schedule for the state-wide maintenance dredging program by the Brisbane varies from year to year and consecutive years are rarely the same. Not all Queensland ports require dredging each year and the volume of dredging required at each port, and associated urgency, depends upon the level of siltation at each port and its operational needs.  

Importantly, environmental risks associated with timing of maintenance dredging, whilst typically low, may also vary annually. Each port has therefore completed a port-specific environmental risk assessment as a key input to the development of the 2024 dredge schedule (consistent with the requirements of the Maintenance Dredging Strategy).

The 2024 dredging schedule may be influenced by unanticipated factors such as weather, dredge breakdown, logistical or provisioning issues. Ports will continually monitor the schedule to determine whether such changes are likely to result in increased environmental risk. In instances where the environmental risk increases, we will be notified, and existing environmental controls reviewed to determine whether they are still effective.

2024 state-wide maintenance dredging schedule by the Brisbane

Month	Location of the Trailing Suction Hopper Dredge Brisbane for Maintenance dredging
January	Port of Brisbane
February	Port of Brisbane
March	Port of Brisbane
April	Port of Brisbane Port of Bundaberg
May	Port of Bundaberg Port of Cairns Port of Weipa
June	Port of Weipa Amrun Port of Karumba
July	Port of Cairns
August	Vessel refit in Cairns Port of Hay Point
September	Port of Hay Point Port of Townsville
October	Port of Townsville Port of Gladstone
November	Port of Gladstone Port of Brisbane
December	Port of Brisbane

To develop the 2024 state-wide dredging schedule, individual ports and the dredge operator considered the following issues:

• opportunities to minimise dredging requirements
• opportunities to minimise environmental risks
• permitting and approval conditions
• volumes of material to be dredged
• urgency of port dredging requirements
• dredge vessel maintenance including refit needs
• economic efficiencies
• response to natural disasters including cyclones and flood events
• reducing carbon emissions.

Minimise dredging requirements

The schedule is best initiated after the wet season when most sedimentation occurs to avoid the need for follow-up dredging. The schedule for this year will begin in mid-April.

Minimise environmental risks

Port specific risk assessments suggest maintenance dredging is a low risk at all ports.  However good practice principles suggest that, for 2024, dredging should be avoided:

• at Bundaberg from October to February when turtle nesting occurs at Mon Repos (this is also a permit condition)
• at Karumba a permit condition requires that dredging only occurs between 1 May and 30 September in any year
• at Hay Point from October to December to avoid coral spawning periods (permit condition prohibits maintenance dredging within seven days either side of predicted coral spawning events)
• at Port of Townsville voluntary limitations are in place from:
  • 17 to 24 October and 16 to 23 November to avoid timing of coral spawning
  • 29 August to 4 September to avoid a local event for navigational safety (note event window subject to change by a few days). 

Seagrass communities at ports vary in condition and extent reflecting environmental conditions (for example cyclones or above average rainfall) experienced over the preceding years with some being in good condition whilst others are recovering or are in poor condition. Many years of dredge and seagrass monitoring indicate no environmental benefit would be gained by restricting maintenance dredging at ports to a specific time of the year.

Permitting and approval conditions

Permit conditions include restrictions on dredging at Bundaberg in the period October to February due to turtle nesting in the area and restrictions on dredging at Karumba from October to April due to prawn migration and turtle nesting.

Annual sediment sampling is being undertaken at the Port of Cairns as part of permitting requirements. As this is yet to be approved, there is no dredging between January and April.

Volumes of material to be dredged

The degree of siltation and its location within the channel, berth or swing basin determines the volume of material to be dredged and the duration of dredging at each port required to restore designated depths. Currently forecast volumes in 2024 at all ports are generally consistent with or below long-term averages with the potential exception of Cairns, which has been subject to heavy flooding and rainfall during December 2023 and January 2024.

Urgency of dredging requirements

The urgency of dredging requirements varies from year to year depending upon the degree and location of siltation at each port. Based on current conditions there are no immediate urgent requirements.

Dredge refit

The Brisbane will undertake an in-water refit for 21 days in mid-August.

Dredge economic efficiencies

The schedule has been designed to ensure ports are visited in a relatively linear fashion and avoid the need to “backtrack” wherever possible. Increased requirements for the dredge to travel between ports results in increased costs (potentially $100,000’s), fuel usage and vessel emissions.

Emergency response

Extreme weather including following Tropical Cyclone Jasper affected the wet tropics region, with possible implications for siltation at the Port of Cairns. In addition, tropical cyclone Kirrily was declared in late January 2024 and may create additional siltation concerns for a number of ports within the warning area including, Townsville and Mackay/Hay Point. The extent of siltation is unknown at the time of writing this document, but ports will be surveyed following the event, and siltation models and dredging needs communicated to the Port of Brisbane Pty Ltd with regards to any updates to the schedule.