Lessons to learn from previous triple La Niña threats | UniSC | University of the Sunshine Coast, Queensland, Australia

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Lessons to learn from previous triple La Niña threats

With regions such as the Fraser Coast and Gympie on alert for a rare third consecutive La Niña, University of the Sunshine Coast flood historian Dr Margaret Cook says there is much we can learn from previous events.

"Expect rain. Lots of rain. And take advantage of warnings to start preparing now," says Dr Cook, whose research focus is the history, recovery and future of flooding in Australia.

"Many households are still reeling from floods earlier this year; the clean-up continues with many houses unrepaired, says Dr Cook.

She says a triple La Niña has only happened three other times in the past 120 years, since national rainfalls were first collected.

“The concern with three successive La Niña years is the increased likelihood of flood at a time when the region’s dams are largely full and rivers high. With a soaked catchment, the runoff rate will be extremely high.”

“History shows that successive floods cause a cumulative emotional, psychological, and financial toll." 

Dr Cook says the latest predictions of more extreme weather could be triggering for some.

"With floods so close together it is also easy to feel flood fatigue, a weariness to coping with disasters which erodes our ability to cope."

Dr Cook says as weather patterns continue to change it becomes increasingly difficult to predict what might be in store.

"The big question is, what are we doing to prepare? Forewarned can be forearmed. Moving in advance saves lives, possessions, and heartache, Dr Cook says.

"As a community we could be mobilising volunteers to help prepare. We need a flood army beforehand, rather than relying on the mud army afterwards to clean up the mess." 

Suggestions include storage sheds on high ground that can store possessions and identifying where vulnerable people live and devising a system of community help.

Dr Cook says if any city paints a picture of the impact of a La Nina triple threat it must be Gympie. It’s worst four flood events occurred during this rare phenomenon, in 1955, 1974 1999 and 2022.

Australia's longest sustained La Niña period on record was the 1970s cluster. "1974 was Australia’s wettest year on record and 1973 and 1975 in the top five,” says Dr Cook.

“The following year, a cyclone brought serious floods to Southeast Queensland at the end of March. Rainfalls of 250 to 500mm over the Mary Valley caused the worst 20th century floods, the peak at Gympie was the highest since 1893, with a height of 3metres in the main street.

“Peak heights at Tiaro and Maryborough were the second highest on record, just under the great flood of 1893 flood. Brisbane too was flooded, the highest floods since 1954.

The 1998-2001 three back-to-back La Niña might not have been brought record breaking floods but there was still widespread above-average rainfall and inundation, especially in Queensland and New South Wales.

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