New South Wales authorities have warned communities at risk of major flooding in the Sydney region to evacuate or prepare to evacuate as the Hawkesbury, Nepean and Georges rivers continue to rise.
Warragamba Dam, Sydney’s main reservoir, was spilling at a rate in excess of 70 gigalitres a day on Wednesday after torrential rainfall over its catchment exceeded earlier predictions, according to a NSW government official.
The spill, which began at about 3am, was expected to peak on Thursday. The previous expectation of an upper range of the spill at 350GL a day has now been lifted to match or exceed the 440GL/day rate experienced during the March 2021 floods. That event caused widespread damage to areas to Sydney’s north and west.
“Major flooding is occurring in south-west Sydney exceeding March 2021 levels with major flood warnings in place. It’s raining, with some areas hit harder than others and more rain on its way. Keep a serious eye on the warnings and forecasts,” the NSW Bureau of Meteorology tweeted before 9pm.
Major Flooding is occurring in southwest Sydney exceeding March 2021 levels with Major Flood warnings in place. It's raining, with some areas hit harder than others and more rain on its way. Keep a serious eye on the warnings and forecasts: https://t.co/2qM1QRn3xE @NSWSES pic.twitter.com/37j66m7iHA
— Bureau of Meteorology, New South Wales (@BOM_NSW) March 2, 2022
“This is our worst fear,” the NSW deputy premier, Paul Toole, said earlier on Wednesday evening. “It will get worse before it gets better.”
In a worst-case scenario, Warragamba’s spill rate could peak at 600GL/ day, Toole told a media conference. A potential evacuation could involve “quite a few hundred thousand people”, NSW State Emergency Service commissioner, Carlene York, said.
Sydney Harbour holds roughly 500GL. More flood water, too, is entering the Hawkesbury-Nepean region from other tributaries that enter the flood plain below the dam.
There were also concerns Redbank Dam could fail, prompting the SES to direct people in some parts of North Richmond, north-west of Sydney, to evacuate.
“We just recently issued an evacuation order for the area in North Richmond downstream of the Redbank Dam because it may fail,” York said. “I want all those residents to make sure they do evacuate from that area.”
Residents were told to evacuate in some areas of Agnes Banks, Bligh Park, Camden, Cattai, Chipping Norton, Georges Hall, Lansvale, Leets Vale, Milperra, Moorebank, Sackville, Warwick Farm and other suburbs.
Authorities also told thousands more residents who were affected by Sydney’s 2021 floods to be on standby to leave.
NSW Health told people isolating due to Covid they should still evacuate their home if threatened by rising flood waters.
“If you are told to evacuate, you must evacuate,” NSW acting chief health officer Dr Marianne Gale said. “An emergency evacuation is a valid reason to leave your home.”
The Bureau of Meteorology shifted its forecast for when Sydney’s heaviest falls may land, predicting 120mm to 150mm on Thursday, up from 50 to 70mm. Since 9am on Wednesday, the city had only collected about 10mm, although inland sites were much wetter, with about 84mm up to 5pm at Richmond.
The bureau has also issued a major flood warning for the Nepean and Hawkesbury rivers.
“Significant river level rises have been observed along the Nepean River where major flooding is possible from early Wednesday evening,” the BoM said.
“Along the Hawkesbury and Lower Nepean rivers major flooding is also possible from overnight Wednesday into Thursday at Penrith, North Richmond, Windsor and downstream based on forecast rainfall.”
“We are going to be getting massive, like torrential rainfall,” Stephanie Heard, a spokesperson for the NSW SES, said.
“We want the community to start preparing for the potential for evacuation. We really need to make sure that the community listens and will follow our advice. Basically, it’s really quite a dangerous weather system that we’re seeing.”
There had already been 18 flood rescues in the Sydney region by Wednesday afternoon. Rainfall totals could reach 150mm to 200mm over the Hawkesbury region, Heard said.
While Sydney itself had been spared most of the heavy rain from the developing east coast low, inland areas including the Warragamba catchment had been receiving big falls.
Ben Domensino, a senior Weatherzone meteorologist, said the rain gauge at Warragamba had collected almost 100mm from 9am to 3pm. By comparison, Sydney’s Observatory Hill near the CBD had only about 30mm in the 30 hours to 3pm on Wednesday.
The rain gauge at #Warragamba Dam has received over 120mm in the last 28 hours, with similar totals in other parts of the dam's catchment area. This includes 48mm in the last 2 hours. pic.twitter.com/y3du5u14hG
— Ben Domensino (@Ben_Domensino) March 2, 2022
“This system has continued to surprise as to the extent of the rainfall,” Domensino said, noting its evolution from a so-called “rain bomb” over south-east Queensland and northern NSW into a low pressure system near the NSW central coast.
“This system at the moment is causing much heavier rain on the ranges than it is near the coast. There’s likely to be some heavy rain near the coast especially as the low pressure system comes in overnight into Thursday morning.”
People who may need to be evacuated should prepare an emergency pack and gather pets, which evacuation centres will be able to accommodate, the SES’s Heard said. The kit should include key valuables but also Medicare and other ID. More details can be found here.
Not surprisingly given the spill from Warragamba, the dam is 100% full, WaterNSW said. The entire dam network is sitting at 99.2% and it’s likely they will all be spilling by the end of this rain event.
Along with the warnings about floods and heavy rain, there are strong wind gusts and dangerous surf forecast, the latter up and down the NSW coast, the BoM said.
