; Two Rocks Sea Wrack Management - Coastal management - City of Wanneroo

Coastal management

Two Rocks Sea Wrack Management

Sea wrack (seaweed and seagrass) accumulation in Two Rocks is caused directly by the Two Rocks Marina which interrupts the alongshore movement of both sand and sea wrack. The beach immediately south of the Two Rocks Marina has experienced ongoing sea wrack accumulation since the construction of the marina, particularly during summer months, resulting in issues with beach usability, public safety and odour. This beach area falls outside of the City of Wanneroo managed land boundary, however a Section 91 licence for the use of Crown Land has been obtained to cover the 2021/22 summer period to enable the City to conduct works on this land during this time.
The Department of Transport (DoT) conducted an assessment of wrack accumulation for this location which confirmed excessive wrack accumulation during summer months and identified metocean conditions which resulted in the transport of the deposited wrack back into the ocean and away from the beach. The DoT Two Rocks Summer Wrack Accumulation Study (2020) can be found by clicking below:

Department of Transport - Two Rocks Summer Wrack Accumulation Study

Based on the recommendations of the DoT study, the City, in consultation with the Two Rocks Yanchep Residents Association, will be conducting a sea wrack management trial from December 2021 to March 2022 involving the following:

  • Regular beach monitoring to determine when the deposited sea wrack becomes an issue;
  • Pushing of the deposited sea wrack back into the ocean using loaders on the beach during favourable weather conditions; and
  • Deployment of GPS drifters into the water with the sea wrack to track sea wrack movements and confirm that the wrack is removed from the beach area.

This project is partly funded by the State Government via the Department of Planning Lands and Heritage 2021/22 Coastwest Grant.

Should you have any queries on management of sea wrack accumulation south of the Two Rocks Marina, please contact the City’s Specialist Coastal Engineer, Mr Rory Ellyard, on 9405 5883

Two Rocks - Sea Wrack Project Map

Two rocks sea wrack project map