Jurien Bay Boat Harbour

The Department of Transport (DoT) is researching how it can improve the harbour environment in the Jurien Bay Boat Harbour.

The Jurien Bay Boat Harbour (JBBH) has experienced seasonal water quality issues that are primarily caused by ingress, accumulation and decomposition of seagrass (wrack) into the boat harbour during winter. Decomposing seagrass leads to oxygen depletion in the boat harbour waters and at times a strong hydrogen sulphide odour. The low oxygen levels typically occur in winter and through spring, leading to occasional fish kill events

Over the past 6 years, Department of Transport (DoT) has completed a comprehensive data collection and research program in order to better understand the physical and biological properties of these events, and to develop an effective solution to the wrack issue. These include coastal modelling studies, data collection, environmental studies and a number of trials including dredging, trawling and more recently the use of a bubble curtain to prevent wrack ingress into the harbour and to oxygenate the harbour water.

Following this large body of work, it was determined that reconfiguring the boat harbour entrance would be the most effective option to investigate as a solution.

  Entrance reconfiguration concept

Modelling studies undertaken show that a structural modification to the northern breakwater by the addition of a large spur groyne proved to be the most effective when modelled against future tides, wind, wave and wrack movement.

The modelling studies showed that by reconfiguring the harbour entrance with the additional groyne, a high percentage of seagrass movement into the harbour should be diverted and significantly improve the water quality within the harbour annually. 

It must be noted that this structural modification will result in some trapping of wrack on the northern beach.

Northern Breakwater modification concept
Northern Breakwater modification concept
Northern Breakwater modification concept
Northern Breakwater modification concept

  Scope and status of the concept

The JBBH entrance reconfiguration is proposed to be delivered by DoT and will require State funding. The 150-metre spur groyne addition to the northern breakwater reconfigures the entrance, and thereby prevents seagrass from entering the harbour. The works will include import of rock material by truck and placement of this material using large earthmoving equipment to construct the spur groyne.

DoT is working actively with the Shire of Dandaragan to explore funding options and opportunities. DoT is currently undertaking a detailed design process for the spur groyne and environmental approvals are being scoped and actively sourced based on the current preliminary design.

  Jurien Bay Boat Harbour maintenance dredging campaigns

Sand and seaweed from the offshore marine environment are transported into Jurien Bay Boat Harbour via natural coastal processes and accumulate within the entrance channel and basin. Maintenance dredging is the process undertaken to remove accumulated marine sand and seaweed in order to:

  • restore navigable depths for vessels;
  • provide ongoing access and operational use of the harbour
  • remove decomposing seaweed and maintain harbour water quality; and,
  • restore natural tidal flushing.

Offshore placement

Jurien Bay Boat Harbour maintenance dredging campaigns are completed approximately every two years. For previous campaigns, dredged material has been placed onshore in a designated area north of the harbour. DoT has been seeking a long-term sustainable solution with dredged material now proposed to be returned to the offshore marine environment into a natural seabed depression.

DoT has secured environmental approvals for this offshore disposal location and dredged material will be placed within this area during future maintenance dredging campaigns.  Maintenance dredging campaigns will be monitored and managed as per environmental approval conditions and the Jurien Bay Boat Harbour Maintenance Dredging Long Term Monitoring and Management Plan.

Offshore disposal location 

Jurien Bay Boat Harbour Maintenance dredging offshore placement
Jurien Bay Boat Harbour Maintenance dredging offshore placement
Page last updated: Fri Sep 30 2022 3:47:42 PM