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Mooloolaba boat harbour dredging

The Mooloolaba harbour and entrance training walls were built in the late 1960's. Since that time, sand shoaling events have occurred regularly in the entrance channel.

Maintaining a safe navigable entrance here is crucial for all boaties. We aim to keep the entrance clear to navigable design depths (depth of -2.5m Lowest Astronomical Tide – LAT) at all times.

Direction of sand transport around Point Cartwright

Channel shoaling

During a shoaling event sand enters the channel where it accretes to form a shoal (like a sand bar). The shoal decreases the water depths making navigation more hazardous.

To improve safety, dredging removes the sand shoal by pumping the sand onto Mooloolaba Beach. The dredge stays in position and continues to remove sand until safe navigation depths are reached. The 2020-2021 shoaling event has required almost continuous dredging since September 2020.

Aerial image of the dredge in the Mooloolaba channel

Current dredging strategy

We have contracted local Sunshine Coast dredging contractor – Hall Contracting to dredge the Mooloolaba channel entrance. A small cutter suction dredge is used, as this plant is manoeuvrable and small enough for boaties to pass safely whilst in use. This arrangement allows a dredge to be available at short notice and on cost effective establishment and standby rates due to rough weather or between shoaling events. Other types and sizes of dredges were not viable for this location.

The dredge remains mobilised in the harbour entrance and dredges continuously when calm weather allows until the shoal is cleared. A permanent pipeline was installed in 2013 along the eastern breakwater wall and then runs across the channel anchored on the riverbed. This makes dredging more efficient with less impact on boaties accessing the harbour. The dredged sand is pumped onto Mooloolaba Beach by the pipeline that runs under the beach. Sunshine Coast Council undertakes dredging works where the primary purpose is the maintenance of the beach as an erosion buffer along Mooloolaba Spit.

Active dredging in the channel with pipeline connected at Mooloolaba

Current dredging work

Since 1 January 2021, the dredge has pumped approximately 70,000m3 of sand from the entrance channel directly onto Mooloolaba Beach.

The entrance channel was cleared to design depths in mid-May 2021 and the dredge was removed for maintenance. The dredge was quickly re-established in June 2021 with dredging works continuing. Design depth was achieved on 24 August 2021.

Hydrographic surveys are carried out regularly to monitor depths. Boaties are reminded that coastal bars are constantly changing. Plan your crossing of the Mooloolah Bar and navigate with caution. Stay up-to-date with the latest Notice to Mariners advice to see if your crossing will be impacted.

The Mooloolah River entrance is designated as a coastal bar. This means that each person on board an open boat less than 4.8m in length must wear an appropriate lifejacket while crossing the coastal bar.

Pipeline pumping sand from the channel and depositing on the beach

Entrance monitoring cameras

In July 2021, we installed cameras to monitor the wave conditions and dredging activity at the channel entrance. The cameras are fixed to the 2 towers at the end of each Mooloolaba breakwater, looking down into the channel. A photo is taken every 15 minutes.

Investigations to a longer term solution

A extension to the eastern breakwater to intercept large shoaling events has been recommended by coastal engineering consulting firm WBM Oceanics Australia. This option was assessed in a 2014 options study. After considering all options a 60m breakwater extension was confirmed as the preferred option in 2018.

Proposed extension to the channel eastern breakwater

In February 2019, coastal engineering consultants KBR started the detailed design work of the 60m breakwater extension. The design was tested at the QLD Government Hydraulic Laboratory through physical modelling using a 1 in 41 scale model. The design was modified and included analysis of concrete armour units for the construction of the breakwater.

Further design and modelling work are now planned to try to reduce the armour sizing of the concrete units and bring the construction cost down.

Physical model testing of the proposed lengthened breakwater

Contact us

If you would like to register your interest in this project and be added to the stakeholder email contacts for further updates, please email the project team: boatinginfrastructure@msq.qld.gov.au

Last updated
10 September 2021