Evacuations, landslides: Thousands hit by storm chaos

Sydney was plunged into chaos last night after the biggest rain event it has seen in 30 years sparked floods, evacuations and landslides.

With NSW experiencing its wettest spell since 1998 the State Emergency Service received more than 3600 calls for help on Sunday alone and 40 people had to be rescued from floodwaters.

Evacuations were ordered in Narrabeen in Sydney's north as well as the southwest suburbs of Moorebank, Chipping Norton and Milperra.

The worst of the storm damage was in Bayview on the Northern Beaches, where a small landslide underneath a two-storey building about 3pm triggered concerns for residents' safety.

No one was injured but police said they had evacuated multiple properties on Kookaburra Cl and surrounding roads had been closed.

Similarly in the Blue Mountains train services were cancelled after the rain washed away soil underneath the tracks at Leura on Sunday afternoon.

Sydney trains issued a warning to avoid all unnecessary travel across the entire network because "trees in overhead wiring & on tracks, external power issues, signal equipment repairs and flooding" had caused extensive delays.

Sydney copped most of the rain as the east coast low moved slowly south, with 160mm of rain falling at Hornsby between 9am and 5pm on Sunday while 129mm was recorded at Parramatta.

It comes on the back of massive dumps of rain in the northern parts of the state, including Kingscliff on the state's north coast where a whopping 282mm of rain in the 24 hours before 9am on Sunday morning.

But the worst could be yet to come, with waves up to 8m high coupled with a king tide prompted Bureau of Meteorology state manager Jane Golding to warn of coastal erosion similar to that seen at Collaroy Beach in 2016.

"(Monday) and Tuesday will be the main danger period, because it is really the height of the waves, the power of the waves coming in from the East which erodes the land," she said.

The king tide was expected to peak at 9.45pm last nigh and again at 9.56am on Monday.

The high tide and surging floodwaters sparked the evacuation of residents near Narrabeen Lagoon, who were warned that if they remained in the area after 10.30pm "you will be trapped without power, water and other essential services and it may be too dangerous to rescue you."

Local resident Carole Lloyd was evacuated by boat from her home on Mactier St on the edge of Narrabeen Lagoon as floodwaters lapped at her veranda.

The 75-year-old grandmother said she grabbed her medicines, her will and her insurance documents before she was helped out by the SES.

"The water was up to the veranda and just about to come into the house."

NSW Ambulance pleaded with motorists not to underestimate the conditions, saying they have responded to five car accidents every hour since Friday night.

In one of the worst incidents, four people were hospitalised after a tree fell onto their car on Bridge St in the city at 1.30pm on Sunday. NSW Ambulance Inspector Giles Buchanan said ambos had been called to numerous incidents where trees had fallen onto cars, houses and people trapped in cars in flood waters.

The State Emergency Service responded to 3660 call-outs across the state on Sunday. On Monday, they will focus their attention to the south coast with fears high rainfall within firegrounds could trigger falling trees and land slippages.

WATER VIEWS TO CRY FOR

Beachfront Collaroy residents were last night crossing their fingers as strong winds, a high tide and an 8m swell combined to threaten a repeat of 2016 storms which eroded the beach and damaged their homes.

"This will be the test tonight," resident Garry Silk said.

"There is a high tide tonight at 9.45pm."

He said the construction of a sea wall for residents along the exclusive stretch of sand had been delayed by government red tape and discussion over who would pay for it.

The council has built a sea wall along a 400m stretch of land where there are council carparks but residents had to fork out about $200,000 each to build their section of the sea wall.

"Four (development approvals) have been issued by the council to private owners but none of us have got on with it yet for a variety of reasons," Mr Silk said.

"We still have some red tape we're trying to sort out with the government."