Sydney Harbour is becoming "cluttered" with boats, prompting the New South Wales Department of Transport to launch the first study into the impact of boat moorings on the health of the waterway.

"It would be great to be able to open up some of the waterways that are currently cluttered with moorings," Howard Glenn, the general manager of Maritime and Transport for NSW, said.

Sydney Harbour is home to about 17,000 recreational boat users, amounting to 8 per cent of registered vessels across the state.

There are 4,850 private moorings in the harbour and demand has increased at a rate of about 3 per cent a year.

"If you look at Rushcutters Bay, that's now pretty much full of boats on moorings," Mr Glenn said.

"Lots of boats on the Pittwater are full of boats on moorings and there's many other parts of the harbour where the bay is actually taken up as a storage facility, rather than as a recreational waterway."


It's the actual mooring line ... that can cause quite a wide area of damage not only to the sea grass, but to the soft sediment system itself.

Professor Emma Johnston, SIMS Director.


The NSW Government is looking at how to improve boat storage without hurting the environment.

Researchers from the University of New South Wales (UNSW) and the Sydney Institute of Marine Science (SIMS) have begun intensive surveys of the sea floor at six sites from Manly in Sydney's north, to Watson's Bay in the east. The project is expected to last three years.

SIMS director Professor Emma Johnston said traditional moorings were a particular concern for sea grass because they carve circular holes in harbour meadows.

"There's a very large block of concrete that usually sits on the bottom which causes a small amount of impact, but really it's the swing," she said.

"It's the actual mooring line and the way it moves through the sea grass bed that can cause quite a wide area of damage not only to the sea grass, but to the soft sediment system itself."

Professor Johnston said half of Sydney's sea grass meadows had disappeared in the last 60 years. One species, Posidonia Australis, or strapweed, is endangered.

"That's not only from moorings, but also from a range of other activities," she said.

"We're particularly concerned about strapweed.


"It's a species of sea grass that has been particularly vulnerable to human activity and it doesn't regrow very quickly.

"In Sydney we have very small fragments of strapweed left in the harbour and we think these populations are very, very precious.

"But there are existing moorings that occur within strapweed beds and we need to find better ways of keeping the boats on the harbour so people can use them, but avoiding damage to our precious sea grass."

The ABC joined technical divers from the UNSW near Nielsen Park in Sydney's eastern suburbs.

UNSW research associate Doctor Luke Hedge said there was "a lot going on" in Sydney Harbour, particularly around the boating infrastructure, marinas and moorings.

"We have big chains going up holding 40-foot yachts, we have hundreds of moorings in a one kilometre square area," Dr Hedge said.

Data to assist transport department in boating management

The research divers have seen evidence the mooring structures can affect the sediment.

Dr Hedge said they were taking comprehensive samples of the sea floor to gauge the extent of the damage.

He said the data could help the Government to implement the best possible management plans for the boating community.

"We're taking sediment samples, we're taking video transects, we're counting the fish, we're going down and looking at the sea grass, we have students taking three dimensional models of the sea floor," Dr Hedge said.

"We want to go deeper. We want to look at not only how moorings interact with sea grass, but also how the moorings can interact with say microbes ... right up to how these moorings can interact with the fish.

We need to work out compromises - the solution that is going to best fit the people, the recreational boaters themselves and the environment.

Professor Emma Johnston, SIMS Director


"All this data we've never had before. So it's really great for the Transport Department to invest to get that data so they can best manage our vibrant boating community."

Professor Emma Johnston said alternatives to traditional swing moorings had also raised potential environmental concerns.

"When you look at the moorings, they have a particular impact on the sea grass. Marinas tend to concentrate contamination," she said.

"And if we put the boats on land they tend to block people's view of the harbour, so we need to work out compromises - the solution that is going to best fit the people, the recreational boaters themselves and the environment."

Hugh Treharne installs and repairs moorings in Sydney Harbour. His father started the business in 1950.

He said too many boats were falling into disrepair and laying idle.

"Sadly they're just cluttering up the bays," he said.


Mr Treharne acknowledged moorings could harm sea grass, but only in shallow water less than 10 metres deep.

And, he said onshore storage solutions could prove to be unattractive and unpopular.

"Those stack buildings that they put them in with a forklift, they're a bit of an eyesore and [on] not too many parts of the harbour [are] people are going to like to see that sort of storage," Mr Treharne said.

"I hope they can come up with some other way."

In July 2015, 41 swing moorings are due to be removed from Clontarf in Sydney's north as part of the redevelopment of the local marina.

Scientists are preparing to monitor the area to see what, if any, recovery is possible on the ocean floor. Their findings will form part of the report to be delivered to the State Government.