DHI Australia has completed an artificial reef for improving coastal protection and the surfing amenity at Palm Beach
Designing a complex artificial reef
The reef design itself has evolved from a rectangular submerged breakwater rotated obliquely to the incident wave direction and with mild seaward facing slopes merging into a conical wave focusing toe.
The design used wave refraction to focus and intensify wave energy towards the shallow crest, and as a result of this, further increase wave dissipation.
The crest level of the reef was set to 1.5 meters below mean sea level to make sure the reef crest remained submerged during low tide, while still being able to induce wave breaking on most swell conditions.
The shape of the reef was carefully designed to make sure that wave breaking on the reef occurred in a continuous and predictable fashion suitable to most surfers.
A rubble mound rock boulder design was chosen as the best option to assure that the design shape could be achieved in construction and that its structural integrity could be assured during large storms.
- not accept the shape of the bottom of the places we surf
- get our local governments to crack a few rocks and make these places better
- place building-waste blocks where they need to be to improve surfing spots OR better still, make places that people can’t surf into places where they can.
I can give examples but what do you think?
In NSW in the 1930s and 1940s there was a massive building, especially around Sydney, of swimming pools on the coast, they were hewn out of rock on the tidal platforms. Why don’t we do something similar to make/improve surf breaks?
Gold Coast QLD Narrowneck artificial reef
The Gold Coast Council is spending more than $2 million to revamp the offshore artificial reef at Narrowneck using another 70 sandbags the size of a small bus.
It is worth looking at this article just to see the specialised boat doing the job.
In an article in The (Hobart) Mercury Park Beach surfer Mr Hollmer-Cross has called for more research to be undertaken.
“There has been no hydrological or environmental assessments on why that spot has been selected as the optimum spot in Tasmania,” he said.
“The surf is really functional as it is, it always has been. For recreational and learner surfers it’s actually ideal.”
That is one of the rules of building artificial surf reefs:
Put them somewhere that no one surfs – there are miles of coastline that fulfill that requirement.
Shane Abel has spent the past three years working on a proposal for an artificial reef at Park Beach, south-east of Hobart.
Mr Abel has done extensive research on attempts to create artificial surf reefs around the world.
Read about how he intends to construct the “reef” in this article by ABC:
Shane Abel on Facebook:
Editied from the Facebook page:
The reef is constructed from HDPE, the same material used in fish farm cages. The reef is supported on timber piles and is above the ocean floor and not interfering with the littoral drift or sealife that live in the sea beds.
The Wavebuster HDPE reef surface can be designed to match any world class reef within 20mm. The reef slope can be set at any angle to incoming swell with 45 degrees being the middle ground with increased angle producing faster waves and decreased angles producing slower waves.
Construction of the reef is simple with the piles driven from a barge and the reef fabricated onshore then floated out and sunk into position.
Unlike rock or sandbags the Wavebuster reef can be removed easily if there any issues.
Gold Coast City Council (in Queensland, Australia) have a Surf Management Plan that includes:
- strategies to maximise enjoyment and minimise conflict between beach user groups (e.g. seasonal adjustments to flagged swimming and board riders zones)
- new coastal capital works projects will give consideration to both coastal protection and where possible, enhancement of surf amenity.
They announced in June 2016 that $4.5 million has been set aside to start the Palm Beach Shoreline Project and build an artificial reef about 400 metres off Palm Beach. It is expected to take four years.
See also the previous story (July 2015):
Note that Australian Coastal Walls are selling the ACW Geo-Block beach protection system. More about that on their web page.
For a longer term view of Gold Coast coastal management: