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   Nov 21

Gold Coast beach erosion plan: Is the plan on the right track?

Gold Coast beach erosion Photo: Supplied Durban seawall protection Photo: Robin Candy
Nanjing Night Net

The Gold Coast has a plan for management of beach erosion. Photo: Wes Palmer\

Relaxing before the storm – Surfer’s Paradise beach Photo: Peter Braig

As the 2015 summer storm season approaches, has the Gold Coast City Council got the right plan in place to protect the beaches luring the 11.5 million tourists, residents and investors to Australia’s playground each year?

Two years ago – in June 2013 after three years of storms – Gold Coast City Council launched its “Three-Point Plan for Coastal Protection”, part of its high-profile 10-year Ocean Beaches Strategy.

The “Three-Point Plan” promised $30 million over two years until June 2015 to build a mix of new seawalls and dredging sand from locations off the beach to re-nourish Gold Coast beaches.

In a nutshell it wanted to bring forward two to three decades of beach protection work; with $15 million from the Gold Coast City Council and $15 million from the previous State Government.  However, the state government never provided money to the plan.

Why is preventing beach erosion on the Gold Coast important?

The Gold Coast is susceptible to rising sea levels, a 2014 Climate Council of Australia report “Counting the Costs – Climate Change and Coastal Flooding” found.

The study by Professor Will Steffen, Dr John Hunter and Professor Lesley Hughes was a collation of previous research.

“A 2009 study by the Department of Climate Change (DCC) estimated that there are 2,300 residential buildings located within 50 metres of sandy coast and 4,750 within 110 metres,” the report found.

“This exposes between 4,000 and 8,000 private dwellings to the impacts of coastal flooding if sea levels were to rise by 1.1 metres, whilst a five-metre rise would flood most of the developed area.”

Alarmist perhaps, but that is largely why the Gold Coast City Council’s Three Point Plan was bought forward.

It is the latest approach to protecting Gold Coast beaches after eight savage storms in January-July 1967 smashed Gold Coast beaches and prompted a seawall construction project called the “A-line.”

The Gold Coast’s “A-Line” is effectively a line on a map of the Gold Coast where the worst beach erosion got to in 1967 and where a 16-metre deep seawall was built in the 1970s and 1980s.

June 2013 – Inside The Gold Coast’s two-year, ‘Three Point’ beach protection plan

The 2013 two-year plan suffered an early setback when the previous State Government refused to contribute $15 million to the plan.

Gold Coast City Council however pushed ahead with a revised series of projects.

The Gold Coast City Council decided this was the way ahead:

1. Public Seawall Construction

2. Northern Gold Coast Shoreline Project

3. Burleigh to Kurrawa Shoreline Project

Overall the plan is to add to the existing A-Line seawall and allow the new seawall to be covered by dunes of sand and vegetation and only exposed by erosion during bad weather.

In summary that meant building new seawalls at Miami, Palm Beach, Broadbeach, Main Beach, Currumbin, Tugun and Surfers Paradise in two projects.

It also means progressively “re-nourishing” beaches from Burleigh, Miami, Nobby Beach, Mermaid, Kurrawa, the Gold Coast Seaway and Broadbeach from off-coast sand “banks” which receive sand from the shore in good weather.

The next step is the Palm Beach Shoreline project, which has irritated some residents and surfers.

June 2015 – two years on – what has been achieved?

Over the past two years the Gold Coast has built additional public seawalls at Broadbeach (850m), Main Beach (350m), at North Kirra (1465m) and along the southern stretch of Bilinga Beach (1240m).

Over the past two years the Gold Coast City Council’s teams have checked the condition of the existing 16-metre deep, six-metre wide seawall – the A-Line.

“Investigative peel backs earlier this year exposed small sections of existing seawalls in order to determine the condition of the structures,” a spokesman said.

At some stage in the past car bodies, concrete chunks, logs and rocks were dumped to try to save homes.

Almost four kilometres of this A-line has been certified as operating successfully by engineers, which the Council says is saving the city $15 million.

“Not having to reconstruct 3.9km of seawall has saved the City approximately $15 million,” the spokesman said.

Where are they working now?

The new section is a 125-metre seawall being built at Palm Beach near 27th Avenue and the Esplanade at a cost of $1.1 million.

“The works are scheduled for completion in September 2015 and are being carried out by the City’s construction team,” the spokesman said.

Gold Coast’s future works for the next two years

Main Beach, Narrowneck, North Burleigh, Northcliffe and Surfers Paradise.

This link details how the seawalls are designed and built at Broadbeach; and at Palm Beach; where there has been delays – with some residents questioning how much they should be contributing.

The project will not be finished until August or September 2015.

What do the experts say?

Peter Nielson is a Professor in Coastal Engineering at the University of Queensland and believes while the strategy overall is good, a number of questions need to be asked.

Professor Nielsen said questions remained over the quality of the Gold Coast’s original boulder seawall, the A-Line.

“It is under the sand in most cases,” Professor Nielsen said.

“And parts of that are considered to be properly designed and constructed, and there are other parts that are not,” he said.

He said it needed to be further examined by Gold Coast authorities.

“There is some concerns that it hasn’t and won’t be up to the job – in some areas where it has been privately constructed – whenever there has been a bad storm.”

Palm and Mermaid beaches are the main areas of concern, he said.

In some cases residents built seawalls at their own expense to protect their ocean-front properties, in some cases Gold Coast City Council build the seawalls using levies from ratepayers.

“But that is definitely something that is needed and needed fairly urgently, I think.”

Professor Nielson said the beach nourishment plans were working well but he had concerns about the artificial reef and beach at Narrowneck on the Coast’s north.

“The Narrowneck bank was meant to have a sheltering effect on the beach behind it, providing a surfing locality,” he said.

“But it never really worked in most people’s opinion.”

Professor Nielsen said he asked six months ago for more information about the proposed new artificial reef – built from boulders – off Palm Beach.

Gold Coast City Council proposes $16.9 million be spent on what is called the Palm Beach Shore Project, but that also needed a 50-per-cent subsidy from the Queensland Government.

“But I am not sure where that is heading at the moment because of costs and some safety concerns,” he said.

“I think it was quite questionable about whether it was going to provide value for money,” Professor Nielsen said.

“And also, there were concerns about safety about construction and people could hurt themselves while they were surfing and get thrown onto the rocks.”

Professor Rodger Tomlinson – who has advised Gold Coast City Council on its plan – said within constraints – the Gold Coast’s three-point plan was working.

He said the lack of state government money meant changes from the start.

“So the project in the way it was conceived as a ‘Let’s get in there full-on and get lots of things done straight away’ hasn’t happened,” Professor Tomlinson said.

“But the framework is driving what activities that are going on within the city,” he said.

Professor Tomlinson said it was not appropriate to yet measure the success of the project because it was scaled back without the state government funding.

“The people are definitely seeing the work that is going on with the seawalls,” he said.

“They city has a very active beach dune revegetation program, looking after the dunes.

“So all the good things are happening and they are ongoing.”

Would interlocking concrete blocks provide a better seawall protection than boulders or geotextile bags?

Several private companies have proposed a range of large interlocking bricks be used on the Gold Coast instead of big boulders or geo-textile bags.

Professor Tomlinson said only the Narrowneck reef (2000) and a groyne at Kirra (1980s) were built using geotextile bags and both were now covered with sand.

He believes the bags – a Gold Coast initiative – suit the natural cycle of sand flowing out to offshore sandbanks during bad weather and returning to the beach in good weather.

Professor Tomlinson said large boulders are used because they are easily accessible and cheap.

“But as we move into an era where it is harder to get big rocks, other techniques are being considered,” he said.

“And certainly around the world concrete devices and similar things are being considered.”

Patrick Johnson is a South African businessman – now living in New South Wales – who wants to introduce a system of interlocking brick walls used on South Africa beaches to the Gold Coast.

Patrick Johnson founded a company called Australian Coastal Seawalls and has recently had Manly’s Hydraulic Laboratories, a division of the New South Wales public works department, test his seawalls.

Patrick Johnson has twice approached Gold Coast City Council for a trial.

“Manly Hydraulic Laboratories said this product would withstand a 1 in 100-year event and in a catastrophic event it would not suffer more than one per cent damage,” Mr Johnson said.

“They are interlocking concrete blocks specifically designed to stop erosion,” he said.

“They capture sand, and they line the back of beaches.”

Mr Johnson said the concrete blocks, can be dyed to match the surroundings and said the walls are angled back to capture the sand in the water.

“The overall wall is angled back at a 65-degree angle and the water follows the line of least resistance, so the wave baring sand runs up the wall and the water subsequently drains back to the ocean, but the sand is captured in the blocks.”

He said sections of his interlocking block walls did not tumble from the seawall in heavy swells like boulders.

“It requires very little maintenance and because the blocks interlock they don’t tumble in big surf,” he said.

“Then they have to replenish. We don’t have to do that.”

Professor Tomlinson acknowledged boulders did get dislodged during storms and said there was nothing “fundamentally wrong” with interlocking concrete barriers if they were designed properly.

“It is just the Gold Coast City Council’s current policy is to continue to use rock,” he said.

“No-one has a particular thing against concrete block units.

“It is just that in the current situation on the Gold Coast 99.9 per cent of the seawall are built out of rock, so we want to continue building out of rock.”

“To suddenly put concrete in there might look a bit different, if it got exposed.”

Patrick Johnson said he has had two meetings with Gold Coast City Council staff but wants the chance to press his case with councillors.

Mr Johnson believes his system carried similar costs – around $1 million per kilometre – as the Gold Coast’s seawall program when ongoing maintenance was taken in to account.

Beach erosion experts say these interlocking walls are designed to be “in front” of the sand dunes, not covered by sand.

Patrick Johnson says his interlocking block walls are designed to be either buried or used in front to retain land.

“They can be buried, completely buried,” he said.

“It can be either or, as the situation demands.”

Professor Peter Nielsen said interlocking brick walls could be more popular on the Gold Coast if natural rock boulders were not readily available to the Gold Coast.

“That would be one reason for doing it, otherwise I think the economics of it would rule it out,” he said.

“They can be designed to be equally good. So I would say the difference is in the economics.”

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