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2016 Australian port or terminal of the year

port-of-the-year

Dredging

What is Dredging?

Dredging is the removal of sand, silt, mud and rock that collects (via wind or wave action) on the bottom of a body of water (like a river or sea bed) that has collected through natural processes on the sea floor.

Why is dredging required at the Port of Townsville?

Dredging is required to keep the channel between the port and the ocean at an acceptable depth for ships to be able to safely access the port.
Cleveland Bay is a naturally shallow and turbid bay with most of it having a depth of less than 10 metres of water.

Each year, sediment is deposited into the shipping channel and Cleveland Bay from the Burdekin River, Haughton River, Ross River and Ross Creek.

To keep the channel passable, the Port of Townsville has been carrying out maintenance dredging at least once a year since 1883 to allow continued shipping access to our region.

By law, the Port of Townsville is required to maintain a safe shipping channel into the waters off Townsville to ensure an efficient port services the community of the region.

If dredging was not allowed to happen, ships would be prevented from accessing the port and operations would stop. This would mean no supplies could get through to Townsville like fuel, oil, gas, food, clothing, building materials etc.

Our surveyors use specialist equipment and carry out detailed hydrographic surveying four times per year. These surveys assess the depth of the water around the port and monitor the volume of sediment accumulating in the channel.

The results of these surveys are given to the Maritime Safety Queensland Regional Harbour Master and port users to determine when dredging is required.
The results of the hydrographic surveys are considered against navigational target depths for our port, anticipated shipping trends, and projects or developments that may affect navigable depths.

Where does the dredging happen?

The Port of Townsville is linked to national shipping routes by a 13 kilometre long and 92 metre wide channel. To ensure ships can maintain access to our port, we need to maintain a depth of at least 11.7 metres.

We are also responsible for maintaining appropriate depths so that vessels and boats can access Ross River and the Marine Precinct.

How do we dredge?

Maintenance dredging for the Port of Townsville is carried out by a vessel called the Brisbane. 

What do you do with the dredge material?

Any dredged material that is going to be deposited into an alternate location in the ocean is tested under rigorous requirements in accordance with the London Protocol (an international agreement relating to the disposal of dredged material in Australian waters).

The Port of Townsville’s current site for the placement of dredged material has been in use for more than 40 years and is not located in the Great Barrier Reef Marine Park.

The Port of Townsville does not dispose of dredge material in the Great Barrier Reef Marine Park.

The selection of the current offshore Dredge Material Placement Area was the subject of a comprehensive re-assessment in 1992/93 (in conjunction with the Great Barrier Reef Marine Park Authority and the Australian Institute of Marine Science) with additional research and monitoring undertaken in relation to benthic fauna, hydrodynamics and sedimentation.  The current site and dimensions were chosen for its proximity to key dredge areas, distance from the sensitive environmental receptors, depth past the 10 m contour and location outside of the Great Barrier Reef Marine Park. 

Toxic or hazardous material is not permitted to be disposed of at sea.

Townsville Port Authority Capital Dredging Works 1993 Environmental Monitoring Program