Scientists took advantage of the predicted huge east coast low in June last year to document the before and after shape along 177 kilometres of coastline from Sydney to Coffs Harbour. The scale of the survey was "unprecedented" for a cyclone outside the tropics, they said.

It took just two days for the the beach at Collaroy to go from its widest in decades to devastatingly eroded.

They found the coast shifted an average of 22 metres inland, with almost 12 million cubic metres - enough to fill the MCG to the brim sevenfold - during the three-day event, according to findings published in Nature Scientific Reports.

"The amount of erosion was astounding," said Mitchell Harley, a senior research associate at UNSW's School of Civil and Environmental Engineering.

The impact of the June event, though, was less to do with the storm's intensity - it was about a one-in-five-year event - but rather its unusual direction coming largely from the east.

"When you get particularly unusual waves it really causes huge changes [to the coast]," Dr Harley, the paper's lead author, said. "The whole south-eastern Australian coastal line is in equilibrium, lined up for southerly or south-easterly storms."

While easterly storms are not unknown, climate change is projected to increase their frequency, he said. Homes, roads and even vegetation now usually sheltered by headlands or offshore reefs and islands may be less protected in years to come.

"Certainly, the indications are that storm direction will shift in the future" as the tropical regions expand poleward in both hemispheres, Dr Harley said. "So in Sydney we may see storms more akin to what you see in Brisbane."

Dr Harley made the comments on Thursday from Coogee Beach in Sydney's east, one area that was hammered in last year's event. The local surf lifesaving clubhouse, normally well protected from swells by Wedding Cake Island, copped heavy damage.

The NSW government is in the midst of overhauling its coastal planning, with some residents anxious for an acceleration of the reforms to guide new developments in the wake of last year's storm.

Those changes have sought to take into account projected sea level rise and also the prospect of more intense storms increasing the height of storm surges. Dr Harley said the likelihood of shifting storm tracks should also be considered.

"The coastal hazard lines… are all designed for coastal events of the past," he said. "We need to rethink how we approach coastal planning and maybe these hazard lines needed to be reviewed."