AFTER sea wrack removal trials were carried out at Two Rocks earlier this year the City of Wanneroo is investigating the feasibility of some alternative wrack removal options.
The results of the sea wrack removal trials were presented at a Two Rocks Yanchep Residents Association meeting on May 30.
The first trial was held during a sea breeze event on March 1 with a maximum water level of 1.26m.
The City of Wanneroo’s coastal engineers said once the wrack was pushed into the ocean most of it moved offshore in a northwards direction and then returned the same day.
Sea wrack removal trials were then carried out on March 25 and 28 during an offshore easterly with a maximum water level of 1.23m.
Some wrack appeared to come back soon after being pushed into the ocean, particularly to the south of the site.
There were some challenges with the later trials as the loader was unable to reach the water due to the high volume of sea wrack and soft sand.
The alternative options include a recommendation by the Department of Transport to bury the wrack in the foredune, removal of the sea wrack from the beach for disposal or reuse, doing nothing and a community survey.
The total cost of the trials was $23,325, which was supported by an $8200 contribution from the state government via the Department of Planning, Lands and Heritage.
Wanneroo deputy mayor Brett Treby said the beach immediately south of the Two Rocks marina had experienced ongoing sea wrack accumulation since the construction of the marina in 1973, resulting in issues with beach usability, public safety and odour.
Mr Treby said the sea wrack management trial ran from December 2021 to March 2022 and involved regular beach monitoring to determine when the deposited sea wrack became an issue, pushing 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 wrack to track its movements and confirm its removal from the beach area.
“The sea wrack pushing works were based on Department of Transport recommendations from a sea wrack accumulation study in 2020, which identified weather and tide and wave conditions that resulted in the natural transport of the deposited wrack back into the ocean and away from the beach,’’ he said.
“We are currently investigating the feasibility of alternative wrack removal options.
“Council members and all stakeholders, including the Two Rocks Yanchep Residents Association, will be updated on the outcomes of this investigation.
“A community survey will also be conducted in future to obtain community views on potential sea wrack management options.’’
