Newcastle, Lake Macquarie and Hunter beaches face losing more sand and a future of seawalls, sand nourishment and possible retreat

In some cases, shorelines may have to be moved back as the ocean erodes land.

University of Newcastle researchers are seeking to highlight the issue, amid the need to adapt to a changing climate.

Dr Michael Kinsela, a coastal marine geoscientist, said there were "two different types of beaches in the Hunter".

Beaches south of the Hunter River had bedrock underneath.

"At the moment, they're pretty stripped of sand. There's not a lot of beach at Bar Beach and Merewether," Dr Kinsela said.

Redhead Beach has also been hit by erosion in recent storms, while Blacksmiths Beach has long been considered a storm-surge risk spot.

"On the north side of the river you have Stockton. It is a very different and systemic problem where you have an ongoing loss of sand, as the system has been changed [due to the breakwater and Port of Newcastle]."

Associate Professor Hannah Power said coastal erosion was "very topical now because we've had two La Ninas in a row and there's a risk of a third".

"In these La Nina times, we have more eroded beaches with less sand. That's superimposed on the creeping changes that are occurring with sea level rise," said Dr Power, a coastal scientist.

Dr Kinsela said the erosion of beaches in recent storms provided "an early glimpse of gradually rising sea levels".

"You're going to lose sand offshore more often," he said.

"At the start of July, we had a coastal storm with a low-pressure system over the eastern seaboard. That allowed the water level to be 10 to 15 centimetres higher than it would have been otherwise," Dr Kinsela said.

"That water level allows the waves to attack the beach and dunes."

Infrastructure and roads around beaches mean "there's not a lot of room for movement".

"To maintain beaches over the coming decades and century of sea level rises, good planning will be needed."

Seawalls, like a $10 million plan at North Cronulla, are an option. Seawalls in the "frontal dunes" would mean "periods where the beach is stripped of sand and the water will wash up to the wall".

"The key with a seawall is having a sand management plan," Dr Kinsela said.

This would establish a "proactive process to put sand back to help the beaches recover" after a big storm.

He said sand nourishment would be an option but "not on the scale of the Stockton approach", as it was a bigger and different problem.

He gave examples of places like Newcastle and Wamberal on the Central Coast.

"If you put a seawall there and you have a big storm and the sand gets moved offshore, it will come back of its own accord. But it might not come back quick enough for the community's expectation," he said.

"Do we wait for the sand to come back naturally and will the community be happy with that? Or do we have an expedited process and say we want it back for summer, as it's important [for recreation and tourism]."

Dr Power said stormy summers are more likely during La Nina. This meant beaches that erode in winter "don't have time through the summer to recover".

Dr Kinsela said some beaches might require sand to be trucked in after a storm. In some cases, though, seawalls and sand management may not be viable. Some beaches may have to retreat, with infrastructure moved.

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