The Dog Beach section of Noosa Spit showing the red zone where a seawall may be eventually built.
The Dog Beach section of Noosa Spit showing the red zone where a seawall may be eventually built.

Saving the Spit: $4M erosion plan, seawall on cards

NOOSA Spit's erosion management plan is likely come at a cost of at least $4 million including sand nourishment over 20 years and could involve the eventual construction a seawall.

That is the forecast expenditure by council's foreshore erosion expert Daniel Wishaw, who is asking councillors to endorse his plans for a first stage $1.2 million spend to be put up for consideration in next year's budget.

This follows the completion of the technical studies of the Spit Erosion Management Plan with the findings to be sent out for public consultation and stakeholder engagement.

Mr Wishaw at this Monday's council committee meeting will present a proposed SEMP implementation pathway for erosion management which contains three zones and two "trigger lines" based on sand movements along the Dog Beach section of the Spit.

This is the Spit section where a sea breakthrough is most likely.

"The first trigger line was established based on the 2016 shoreline position, before erosion accelerated, and allows a limited recreational beach and a suitable sand buffer for the protection or re-establishment of vegetation," Mr Wishaw said.

"The second trigger line is the minimum width of the Noosa Spit within which a seawall may be constructed.

"The proposed pathway is intended to maintain the beach width in the green zone for as long as feasible and delay, as long as possible, the need for a structural sea wall at the edge of red zone (running the length of the Spit).

His management plan proposes "a two-staged intervention pathway" with stage one creating "a sand plug at either end of the Doggie Beach".

Stage two would see the beach nourishment "monitored and evaluated with respect to the trigger lines".

 

An overview of the Noosa Spit erosion sections where council is looking at implementing a nourishment program.
An overview of the Noosa Spit erosion sections where council is looking at implementing a nourishment program.

 

This sand replacement would be repeated when the shoreline eroded into the designated yellow zone" possibly five to eight years after the first intervention. He expects sand nourishment would have to be undertaken on average about every seven years.

"If beach nourishment becomes ineffective/unfeasible a seawall could be constructed," Mr Wishaw said.

This would be along the red zone line.

He also recommends a series of complementary activities to "reduce future erosion, including beach access management, vegetation management and replanting as well as community education and consultation".

Since his last quarterly report in September, Mr Wishaw said the shoreline at Noosa Spit has remained fairly stable, "with a review of recent aerial photography indicating negligible change".

"The lower estuary is in a phase which appears to be favouring the formation of a central channel, which typically alleviates pressure on the Dog Beach section of Noosa Spit," he said.

"However, there has been significant volumes of sand that have migrated into the river from both the southern side, and more recently, the northern side which may block this channel in future.

"At present the state of the lower estuary would make the proposed mitigation solution easier to implement, given that the central channel is naturally opening."

This report will go before Thursday night's last council ordinary meeting of the year for a final vote.