Sydney's northern beaches lost up to 40 metres of coastline in the massive storms that pounded the NSW coast on the weekend, and it's not over yet.
It has been 40 years since Sydney has seen such fierce storms and the residents of beachside communities like Narrabeen and Collaroy have been left counting the cost.
Mitchell Harley, a senior research assistant at the University of , told SBS News they had just recently measured Narrabeen's coastline as the widest it had been for 40 years.
Up to 10 to 15 metres of waterfront land washed away at Collaroy overnight as residents return to their homes to assess the damage after being evacuated on Sunday night.
"Within three hours we had a garden that was just totally destroyed - gone," a woman told Network Seven as she looked at her home from police tape as the sun rose on Monday.
"I never thought it would be this bad."
"If you are standing in the garden, you would see cracks coming in. It was just washed out to sea," another female resident said.
Dr Harley said a combination of factors created a perfect storm situation for the northern beaches.
"Large waves are not uncommon here but we had large waves coming from a direction that was particularly concerning," Dr Harley said.
"Normally the waves come from a southerly direction, but for this they were coming from an east to north-easterly direction which meant a lot more waves were coming in to the normally protected southern ends of the beach which creates a lot of destruction.
"This was combined with a king tide - the largest tides of the year."
Dr Harley said several homes that have been partially washed away and had the land eroded out from under them were previously 20 metres from the water.
"[Some homes] have erosion going 15 metres into their backyards and we saw pools and a shed get claimed by the sea," he said.
Residents from seven beachside homes and a unit block were evacuated at about 8pm on Sunday night as eight-metre waves slammed the coast leading to major erosion.
An in-ground swimming pool has been swept on to the beach while several million dollar homes hang precariously on the edge of sand cliffs.
Collaroy Surf Club was severely damaged by the pounding surf and the second storey balcony of the nearby Collaroy Beach Club is collapsing on to the beach.
SES engineers will assess the damaged properties on Monday.
Dr Harley said waves of up to eight metres were still pounding the coast and another high tide was expected.
He said homes that had already been partially damaged would be in serious danger if another storm were to hit to coast in the next couple of weeks.
"We're keeping an eye on future events and we're coming in to a La Nina period, which is particularly concerning because it will mean more storms and greater potential for erosion," he said.
Dr Harley said some engineering work might be needed to rebuild the beach at Narrabeen where sand dunes that would take up to 50 years to rebuild naturally have been washed away.
Other parts of the beach would be able to rebuild themselves over a couple of years.
- with AAP
