Parts of the NSW south and central coasts will have to endure another 24 hours of damaging winds, rain and huge waves as a second east coast low in as many weeks continues to pack a punch.

In Victoria, parts of west and south Gippsland have been told to brace for up to 75 millimetres of rain, while the far east of the state can expect up to 120 millimetres and a flood warning is in place.

NSW Bureau of Meteorology forecaster Shuang Wang said the deep low pressure system off the Illawarra coast was expected to remain slow moving on Monday, with peak wind gusts in excess of 90 km/h.

They were likely to extend to the coastal fringe of Sydney, and possibly the Central Coast, but are expected to gradually ease by Tuesday morning as the low weakened, BOM meteorologist Shuang Wang said.

“This system is weakening in trend but is still significant,” Ms Wang said. “By tomorrow evening [Tuesday]  there will only be a remnant along the coast as it moves east.”

The system has already wreaked havoc along the coast with damage to at least 18 homes on the shoreline at Wamberal on the NSW central coast. Council workers piled up 150 rock-filled bags to stop further erosion and mitigate further damage to residents’ homes.

One Wamberal resident told the ABC: “We are very, very anxious. It has happened before and unfortunately it is happening again now where we have two east coast lows, basically back-to-back”.

“The next 24 or 36 hours is really critical because it is forecast that this will go on through the rest of the day and into tomorrow, so that is the critical period for us right now,” he said.

Transport services were also widely disrupted on Monday morning, with the Manly ferry service suspended and replaced by buses, and trains on the South Coast Line between Wollongong and Port Kembla on Monday were also suspended and replaced by buses due to flooding.

The SES warned the Hawkesbury might experience flash flooding also, while the Illawarra and South Coast regions are on high flood alert.

The BOM said locations that might be affected include Sydney, Wollongong, Nowra, Bowral, Batemans Bay and Eden.

Tweet from @BOM_NSW

Earlier, the BOM said multiple locations across NSW’s south east had recorded more than 100 millimetres of rain in the 24 hours to 9am on Monday, triggering flash flooding and numerous rescues.

Sydney’s Observatory Hill clocked about 72 millimetres of rainfall from 9am Sunday, while Sydney’s Olympic Park had 76.2 millimetres.

In the Sydney basin, Wahroonga received 114 millimetres, while Prospect, south-west of Blacktown, received 101 millimetres.

Elsewhere, Nords Wharf had top falls since 9am Sunday, with 187.5 millimetres falling in the Lake Macquarie suburb.

Jervis Bay had 178.6 millimetres of rain, while Wyee on the Central Coast has received 167.5 millimetres.

Tweet from @BOM_au

The SES have recorded more than 1000 requests for assistance since Saturday, commissioner Carlene York said, including 560 calls from the northern and central coasts.

“The weather conditions have created some risk for our community, particularly in relation to damaged roofs, fallen trees and an increased call for sandbagging across the coastal areas,” Ms York said on Monday.

“We expect some increased winds … that again will bring risk to trees down and perhaps wires down and impacts on electricity services.”

The SES commissioner also said there had been more than 20 flood rescues since Saturday.

Weatherzone meteorologist Ben Domensino said they had recorded some “high impact weather” along eastern Australia with a total of 200-250 millimetres of rain in south-east Queensland and eastern NSW in the past few days.

Wave heights of almost 11 metres and wind speeds of 110km/h were recorded near Bateman’s Bay on Monday morning.

Tweet from @Ben_Domensino