“Basically, the next few hours will be critical,” he said. “After that, the risks will drop significantly.”
Impact from this event appear similar to the 2007 storm – often remembered for the beaching of the Pasha Bulker freighter near Newcastle – but not as severe as the 2016 east coast low that famously dislodged a swimming pool, Dr Harley said.
Waves, while reaching 6 metres, were not as high as in 2016, and winds were also not as strong and more from the south, sparing Collaroy-Narrabeen from worse damage, he said. UNSW has had a permanent monitoring site overlooking Collaroy-Narrabeen since 2004.
As a rule of thumb, beaches in the area can recover about a metre of sand every ten days, so the region will take months to recover.
That assumes, though, that another storm doesn’t eventuate, and there are some indications of a further threat of beach erosion emerging by next weekend, Dr Harley said. The source would be tropical cyclone Uesi, which has formed in the Coral Sea.
Some models indicate it could veer towards the eastern coast of Australia, he said.
At Ramsay Street overlooking Collaroy Beach, bemused locals looked at at a massive build up of sea foam. The cream-coloured foam was mid-calf deep at the end of the road.
Veteran surfer Don Norris, who started the website realsurf.com, said he hadn’t seen it as extensive before.
“I have seen sea foam before but just not this much,” Mr Norris said. “I wasn’t planning on surfing today because of all the storm water run off; I don’t go in for at least a couple of days after the rain.”
One resident who lives in an apartment across from the properties overlooking Collaroy Beach that were devastated in 2016 had a different take on the storms.
“Because we live across the road we are always hoping these houses will fall in [to the sea] and the land reclaimed so we get ocean views,” Fiona Foster joked.
Kristen Hansen, from Collaroy, said she had never seen sea foam before.
“It’s incredible. I am down at the beach all the time but [have never seen] anything like this.”
Dr Harley said Monday should see the “first test” for a temporary seawall built after the 2016 storm. That wall – in effect, a “giant sandbag” – had been buried by sand in the years since that event, and would now likely be exposed, he said.
Helen Reid, a duty forecaster with the Bureau of Meteorology, said models indicate more wild weather may indeed by on the way to the NSW coast.
Meteorologists are watching the newly formed tropical cyclone Uesi near Vanuatu in the south Pacific and Coral Sea region, with indications that storm will track “closer to the NSW coast than elsewhere”.
It could be days before impacts are known but “the bulk of the action will be offshore”, Ms Reid said. For eastern NSW, rainfall totals next weekend would be more like follow-up falls “rather than the deluge we’ve just seen”.
By the time impacts are felt in eastern Australia, the system would likely have become a so-called Tasman low, pressure system, transitioning from its tropical cyclone strength.
Peter Hannam writes on environment issues for The Sydney Morning Herald and The Age.
Tim Barlass is a Senior Writer for The Sydney Morning Herald