The deep and complex low pressure system has brought tides washing all the way up to the car park at some northern beaches, with high tides combining to dump large amounts of sand up on the promenade at Thirroul.

Some beaches are showing rock forms which hadn't been seen by locals for many years.

Wollongong's North Beach has lost a large amount of sand - while Stanwell Park is said to have gained sand.

At Little Austinmer, a rock platform has become exposed at the southern end of the beach more dramatically than for more than a decade, when that beach used to have less sand, some locals have estimated.

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The saltwater pool drainage pipe has been fully exposed at Thirroul, while at Scarborough large rocks are now exposed in the middle of the beach, which itself is a fraction of the width it has been for years.

Scarborough Board Riders Club president Christian De Clouett, 44, said he remembered seeing the rocks like that when he was a kid, and estimated it may have been 15 years since the last time.

"We've had a big chunk taken out ... at Scarborough it's really ripped out the beach. The beach is gone," he said. De Clouett said grasses that had been growing near the high tide mark were now gone, a mark of how severely the beach height has been changed.

And the sand movement had improved the surfing. "It's better now it's been taken out the back - it gives you a longer ride and more options."

He said a friend had reported excess sand had been deposited at Stanwell Park.

The southern end of McCauleys beach has been reduced to rock and clay.

It's become quite the talking point for regular beachgoers, as well as many others who have been spending more time at home or walking the beaches.

A Wollongong City Council spokesman said council crews would remove the sand at Thirroul.

"The large swells and high tides also brought sand onto the promenade at Thirroul Beach and, as the conditions subside, council crews will be working shortly to remove this sand," he said.

"Our council crews also will continue to monitor all our beaches to ensure that there are no other issues such as significant scarping that may have arisen due to the large swells and tides."