Waves up to 8m (26ft) high hit Sydney's Collaroy Beach during a king, or spring, tide on Sunday, washing away up to 15m of waterfront land
Three people are dead and more are missing after massive storms flooded rivers, uprooted trees and tore into beaches along Australia's east coast.
Storms continue to batter southern New South Wales, Victoria and Tasmania.
Erosion at Sydney's Collaroy Beach has forced the evacuation of multi-million dollar homes, which are now in danger of collapsing.
In Tasmania, where major flood warnings have been issued for seven rivers, two elderly people are feared drowned.
A man was reportedly swept into the Ouse River from his own backyard on Monday, while a woman was missing after floodwaters inundated her house in the state's north-west.
Rescuers are also searching for a man who was washed off rocks near Sydney's Bondi Beach.
On Monday morning, a man's body was found in the Cotter River near Canberra in the Australian Capital Territory. Police said the 37-year-old was caught in floodwaters at a river crossing.
Police divers also retrieved the bodies of two men whose cars were washed off New South Wales roads in separate incidents.
A 65-year-old man was caught inside his vehicle while trying to cross floodwaters at Bowral, while another man was killed after his utility vehicle was washed off the road on Sydney's south-west fringe.
Northern Tasmania facing its worst flooding in decades on Monday, with parts of Launceston, Latrobe and Railton all underwater.
The Insurance Council of Australia said that insurance companies have so far received 11,150 claims across Queensland and New South Wales totalling an estimated A$38m (£19m, $28m).