Eastern Australia is experiencing its fifth major flood in 19 months.

More heavy rain has flooded 43 towns in New South Wales, 24 in Victoria, and three in Tasmania, and the unusually wet weather is expected to last until 2023. 

Due to flooding in the Melbourne suburb of Maribyrnong on October 14, emergency personnel were on patrol to assist residents in evacuating.  Getty Images | WILLIAM WEST/AFP
Due to flooding in the Melbourne suburb of Maribyrnong on October 14, emergency personnel was on patrol to assist residents in evacuating.  Getty Images | WILLIAM WEST/AFP

Eastern Australia is experiencing major flooding for the fifth time in 19 months as a result of record-breaking rains that are expected to continue into next year.

Heavy rains flooded large swaths of New South Wales, Victoria, and Tasmania in October, killing four people, evacuating thousands, inundating homes and businesses, and cutting off and damaging roads.

In New South Wales, the worst-affected state, 43 local government areas have now flooded, with some floods spanning hundreds of kilometers.

Over 500,000 sandbags have been delivered in recent weeks to try to limit the damage. "We are literally sandbagging the state at the moment," said Steph Cooke, New South Wales emergency services minister, on October 22.


The state has also been severely impacted by four other major floods that have ravaged eastern Australia since early 2021, when the unusually wet conditions began. The extensive damage has made them the most expensive floods in Australian history.

"By the time we get through this event, almost the entire state will have been affected by a natural disaster of some kind," New South Wales Premier Dominic Perrottet said at a press conference on October 24.

This year, Sydney, the state's capital, has received a record-breaking 2.4 metres of rain, which equates to roughly 3 million Olympic-sized swimming pools worth of water. "We not only broke the record, we annihilated it," said Tom Saunders, a meteorologist at ABC, on October 22.

In recent weeks, several parts of Victoria and Tasmania have received record rainfall, causing flooding in 24 local government areas in Victoria and three in Tasmania.

According to Nina Ridder of the University of New South Wales in Sydney, the 19 months of wet weather have been primarily driven by two large-scale weather systems originating in the oceans on either side of Australia.

The first is La Nia, a weather system that forms in the Pacific Ocean and brings rain to Australia's east coast. A rare occurrence of three La Nia cycles in a row since late 2020 has resulted in "basically no stop in the wet conditions," according to Ridder.

The other is the Indian Ocean Dipole, a weather system that occurs in the Indian Ocean and is currently in its negative phase, bringing more rain to south-eastern Australia.

According to Ridder, climate change may also be a factor because every additional 1°C of warming in the atmosphere allows it to hold an additional 7% of moisture, which can then become rain.

"It will take time to quantify exactly how much human-caused climate change has influenced this specific event," says the University of Melbourne's David Karoly.

According to Ridder, the recent wet spell is due to a high-pressure weather system off Australia's east coast that has prevented rain clouds from moving offshore over the eastern states.

She predicts that when La Nia ends early next year, eastern Australia will experience drier conditions. Even small amounts of rain beyond that point, she says, could cause more flooding because the ground is so saturated that it has limited capacity to absorb any more water. "The entire system will require some time to reset and release all of the extra water." 

The floods follow a year of record drought, heat, and wildfires in eastern Australia in 2019 and 2020. This is consistent with government-commissioned modeling published in 2008, which predicted that climate change would lead to "longer dry spells interrupted by heavier rainfall events" in Australia.

"Climate change essentially means that extreme weather events become more intense and frequent," Karoly explains.

The extremely wet conditions contrast sharply with recent hot, dry conditions in the United States, Europe, and China, which are also thought to be related to climate change. 


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