Waterfront homes on Sydney's Northern Beaches could be at risk this week, with wild weather likely to further erode coastline that has already marched back 25 metres.
Waves were already crashing close to properties at Collaroy Beach after last week's wild weather, which saw almost 400mm of rain fall over the Harbour City in four days.
The coast is expected to be hit again this week as Cyclone Uesi makes its way towards Australia, creating swells of up to 5 metres on Friday and Saturday.
ABC News meteorologist Graham Creed said the cyclone, which is passing north-east of New Caledonia, would track south-west towards the Tasman Sea.
"This may produce large swells, which combined with king tides may cause issues for beach erosion, as well as prolong the potential for locally heavy rainfall in showers and thunderstorms," he said.
Mitchell Harley, a coastal hazard expert with the UNSW Water Research Laboratory, has been collaborating with the University of Sydney to monitor erosion changes between Collaroy and Narrabeen on the Northern Beaches.
He said the CoastSnap beach monitoring station at North Narrabeen recorded a 21-metre recession in the coastline following the weather chaos.
Dr Harley said elsewhere the weekend's storms eroded about 25 metres of beach at Collaroy, but the good news was it was not permanent.
"The important thing to note is that it's not lost from the beach, it's a temporary recession," he said.
For every 1 metre of recession, it takes about 10 days for it to naturally recover, he said.
"However, the concern is that the beach is now quite narrow, quite vulnerable to storm events."
He said the research laboratory would watch for large waves caused by Tropical Cyclone Uesi impacting the coast.
Energy companies are still working to restore power to more than 40,000 homes and businesses after the weekend's devastating storms.
The Bureau of Meteorology (BOM) said it was continuing to assess the impact of the cyclone.
BOM forecaster Rebecca Kamitakahara said Uesi would weaken as it moved south.
"It is still likely to bring us some pretty big surf at the weekend — that's one thing we can be sure of," she said.
"It's still a few days away and it's a tricky system to predict. We're keeping a close eye on it and encourage people to keep up to date with all the forecasts and warnings."
The forecast at this stage is for swells of about 2 to 3 metres starting on the north NSW coast on Thursday and increasing to 3 to 5 metres on Friday.ABC