Tuggerah Lakes water quality: Expert panel hands down findings and solutions
Fifty solutions have been put forward to fix the water quality of Tuggerah Lakes, with an expert panel finding we have been “loving the lakes to death”.
Central Coast
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Fifty recommendations have been put forward to fix the water quality of Tuggerah Lakes.
The long-awaited report from the State Government’s Tuggerah Lakes Expert Panel is now complete with research, data and solutions for a way forward.
Expert Panel chair Associate Professor Will Glamore said one of the main issues affecting the lakes was local development.
“You can see all the houses and all the development, people are aware that the Central Coast has been booming in recent times and every one of those things is creating pollutants,” he said.
“One of the most important outcomes within our plans is that the lakes are largely reflective of the local catchment and what comes off the hills and developments are the issue we need to deal with. We are loving the lakes to death.
“We need things like stormwater infrastructure that treats the water before it gets in there … the rehabilitation of our foreshores. People want to see the birds and the vegetation that supports fish life and stopping the turbidity from coming on so sediment doesn’t wash everywhere.
“Little things like that are what’s going to make a big difference and we need to get that into the coastal management program.”
He said while the water quality had improved there was “pressure on the future”.
“We really need to deal with these pressures. Unfortunately there is no easy fix for things like The Entrance or wrack management however we want to create integrated management plans that empower the community to get involved,” he said.
“Through detailed research and our consultation with the community we wanted to highlight that the lakes are a unique ecosystem. They are a highly valued by the community.
“We think Tuggerah Lakes could be a shining example of how things could be done. It really could be best practice in the world.”
Mr Glamore said while dredging helped with creating clearer waters, it did not necessarily help with water quality.
“It’s about fixing what’s coming from the catchments, that’s what will make the big difference,” he said.
He said the pollutants were the cause of wrack moving from the centre of the lakes to the edges.
Central Coast Parliamentary Secretary Adam Crouch said for the first time there was one document encapsulating all the information on Tuggerah Lakes.
“This brings together all the science, research and data. Council and the State Government will work together to ensure Tuggerah Lakes has a bright future,” he said.
“The extensive public consultation conducted by the Expert Panel shows that our community thinks a ‘reset’ into the management of Tuggerah Lakes is required, and this report enables the (Central Coast) Council to do exactly that.”
Environment Minister Matt Kean said development was placing huge pressure on the system.
“There’s stormwater run off, overflow from sewerage systems. We now have 50 recommendations to preserve the lake system,” he said.
Mr Kean said the panel’s work will help form the Central Coast Council’s Coastal Management Program for Tuggerah Lakes which will set the strategic direction for management of the lakes for the next 10 years.
“The Expert Panel’s final report, Tuggerah Lakes Water Quality Independent Expert Panel Review, is the next step in unlocking what actions need to be taken to protect and conserve the Lakes for generations to come,” he said.
The report is currently with the Sate Government which will consider the 50 recommendations.
The Panel was established in 2019 to address ongoing water quality issues and community concern for Tuggerah Lakes.
Why The Entrance Channel won’t be getting breakwalls
A review by Manly Hydraulics Laboratory of more than 20 studies into Tuggerah Lakes and The Entrance Channel dating back to 1987 has effectively ruled out twin breakwalls as a solution to flooding and improved water quality.
Central Coast Council commissioned the review as a “Stage 1” report for its Tuggerah Lakes Entrance Management Study, which will govern the long-term management of the channel.
Council Environment and Planning director Scott Cox said the conceptual models contained in the report describe the complex nature of the processes and management of the Tuggerah Lakes entrance.
“Managing the entrance is a complex issue with no simple solution,” he said.
“It requires a careful balance between reducing the severity of major catchment floods while protecting the lakes from adverse ocean inundation and minimising disturbances to the community, typical lake water levels and the unique ecology of Tuggerah Lakes.”
Administrator Dick Persson said the community would have a chance to provide input about the plans later this year.
However, an analysis of MHL’s review has found any chance for permanent twin breakwalls — such as those at Wallis Lake, Forster, or Lake Illawarra on the south coast — are all but off the table.
MHL’s review found people have been dredging navigation channels through the sand shoals which build up at The Entrance channel as early as 1912 and the channel has been fully closed at least 13 times in the past 100 years.
The review noted a 1994 study by Lawson & Treloar which found the condition of the channel was “the single most important aspect controlling flood behaviour in the lakes”.
A 2013 study by Cardno, which led to an election promise of a 100m long rock groyne on The Entrance Beach, looked at twin breakwalls at 100m, 150m and 200m apart.
“The results revealed that limiting the entrance to a 100m wide opening caused an increase in peak flood levels of about 0.08m,” MHL’s review of that study states.
“Also, it was estimated that the water levels remain elevated for several days longer than other scenarios, with in-excess of 1300 properties around the lake expected to experience over-floor flooding. Therefore, the training wall with an opening of 100m was discarded.”
It further found breakwalls would not impact the flushing of the lake and would therefore not improve water quality, not to mention cost $43 million to build.
“The results revealed that the maintenance dredging of the type already undertaken by council should be continued,” MHL’s review states.
Another study in 2014 found a channel 250m wide would lower peak flood levels 2.23m to 1.92m-1.78m but “maintaining a fully open channel of these dimensions is not physically or economically viable”.
A further report by Cardno looked at breakwalls and removing some of the rock shelf under The Entrance channel.
It found it would lower the water level in the lake and increase tidal flows which could scour the foundations of The Entrance Bridge and cause shoreline erosion along Terilbah Reserve.
A study of breakwalls across NSW in 2016 by Nielsen and Gordon concluded breakwalls at The Entrance would likely increase erosion along North Entrance Beach.
MHL’s review said that study found sand still banks up at the mouth of twin breakwalls but even if it was deep enough to become “self scouring” it would undermine the existing foreshore seawalls at The Entrance, produce ocean floods during king tides or storm surges and at low tide expose mud flats and seagrass beds.
MHL’s review found a dredging program was most likely the best solution.
“The condition of the entrance, including its channels, berm and shoals, acts as a primary control allowing catchment flows to drain from the lake system while also restricting the amount of ocean inundation into the lake system,” MHL’s report states.
Former Central Coast Councillor Bruce McLachlan said he supported a suggestion by coastal engineer Angus Jackson to trial geotech sandbags as temporary twin breakwalls to see what effect they had.
He said at a cost of about $300,000 the geotech breakwalls could be easily removed if they were found to be ineffective.
“Often these reports are designed to rubbish the most expensive option so nothing gets done, whereas there are other cheaper options,” he said.
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