Thousands of people in low-lying areas around Sydney are being asked to evacuate another an east coast low threatened to trigger the region’s third major flooding since March.
Heavier-than-forecast rain in Sydney’s west – including more than 230mm collected in less than 24 hours at Lucas Heights – has prompted authorities to reassess the flood risks. Major flooding was already happening at Menangle on the Nepean River and similar outcomes were expected in the Hawkesbury-Nepean River downstream.
The New South Wales State Emergency Service overnight issued emergency alert text messages to communities along Hawkesbury-Nepean catchments in preparation for potential evacuations overnight and over the coming days.
The SES received more than 1,000 calls for assistance overnight and conducted at least 26 rescues.
The areas receiving alerts were: Menangle, Liverpool, Milperra, Camden, North Richmond, Wallacia, Penrith, Sackville, Upper Colo and Windsor. Parts of Camden and Wallacia received evacuation orders on Sunday morning, with more expected.
Rain totals in the 24 hours to 9am Sunday AEST reached 93mm for Sydney’s Observatory Hill, while Camden in the city’s south-west reached 156mm. Both Lucas Heights and the Holsworthy defence site received about 240mm.
The Bureau of Meteorology issued multiple warnings of severe weather and also flood warnings for the region.
“An east coast low lies off the Mid North Coast of NSW and is directing humid air and areas of moderate to heavy rain across the central east of the state,” the bureau said.
“Moderate to heavy rain should continue in parts of the central east throughout Sunday, and may continue through Monday as well if the low approaches the coast.”
The heavy rain could bring flash flooding, with six-hourly rainfall totals between 70 to 120mm possible, the bureau said.
For Sydney, rainfall totals could reach 150mm on Sunday, while Penrith in the city’s west may collect as much 200mm.
Warragamba Dam, the city’s main reservoir, started spilling at about 2am Sunday, local time, when it exceeded full capacity earlier than expected. Two days ago it was already about 97% full and did not need much inflow to spill into the Hawkesbury-Nepean River.
Authorities were witnessing outflows from Warragamba at the rate of more than 240 gigalitres a day early on Sunday, and warned they may approach the 400 GL/day rate reached during the peak of the March 2021 spill. In March 2020, they peaked above 500GL/day.
“Inflow to the dam [is] occurring at a rate of 380 GL/day,” WaterNSW said in a statement. “These figures will continue to rise.”
“Access to the dam precinct is closed due to the risk associated with flood operations,” it said.
Flood levels were already at minor, and rising, at Richmond on the Hawkesbury River on Sunday morning and were likely to head towards major flooding levels.
With the east coast low, winds are also a threat, as is damaging surf along the mid-NSW coast pointing to another bout of beach erosion.
Those winds are forecast by the bureau to average 65km/h, with peak gusts in excess of 90km/h likely along the coastal fringe, “most likely during Sunday afternoon and evening”.