River Murray towns have slow wait for flooding disaster to strike

Australia’s slowest-moving catastrophe is in full swing along the southern end of the River Murray, with South Australia’s downstream towns set to be inundated one by one from December 4 ­onwards.

A truck travels across the swollen river at Mannum, which is preparing for floodwaters to peak on December 28. Picture: Matt Turner

Australia’s slowest-moving catastrophe is in full swing along the southern end of the River Murray, with South Australia’s downstream towns set to be inundated one by one from December 4 ­onwards.

South Australians are both fearful and fascinated as authorities try to establish how much water will make its way down the mighty Murray from the eastern states, with the river’s history providing many markers as to how treacherous things could become.

From Renmark to Mannum, every town along the SA end of the river has been here before.

On current expectations, the deluge will be comparable to the 1974 flood, which, as with today’s weather patterns, coincided with a La Niña event.

But there is an alarmingly high chance that things could be as bad as 1931, and possibly even 1956, the worst recorded flood, when lower-lying towns such as Mannum had their main streets engulfed and water remained for six months, crippling the punt service and forcing people to travel hundreds of kilometres to cross the river.

Work carries on to construct a levee to protect the town of mannum, on the southern end of the River Murray. Picture: Matt Turner

While the scale of the impact is unknown, one thing everyone agrees on is that many shacks and some permanent residences and businesses will be lost, almost all of the river’s punts will be disabled, and the clean-up could stretch for months as the sodden banks struggle to absorb the deluge.

The mood in SA currently feels a bit like the 1950s B-movie, The Blob, where an unstoppable, ­malignant force slowly makes its way towards town after town.

SA has reinstated the same emergency powers used during Covid, with Police Commissioner Grant Stevens resuming as State Commander, giving police the power to co-ordinate the defence and recovery effort and make snap decisions such as cutting off power to engulfed regions or ­ordering people to evacuate.

“This is going to be a long event,” Mr Stevens told The Weekend Australian.

“We are talking months of ­inundation which is going to cause immense damage. It’s going to ­affect the environment, physical infrastructure, people’s wellbeing and livelihoods.

“Businesses, the agricultural sector, irrigators, tourism, all of these areas are going to be heavily impacted. We are planning for that already, because we know it’s going to happen.” Mr Stevens said he had been in contact with the ADF and, while the State Emergency Service and police were on top of things now, he could foresee the military being deployed when the water eventually came.

The ability to predict what will happen is reasonably precise thanks to a mix of modern technology and old-fashioned historical knowledge from floods that have happened many times before. As such, authorities can predict the week-long peak periods for all the major river towns.

Heading south from the ­Victorian border, the town of ­Renmark will be hit first, with the river peaking between December 4 and 12. The peak will hit Berri from December 10 to 17, Loxton from December 11 to 18, Waikerie from December 17 to 24, Morgan from December 20 to 27 and Murray Bridge from December 22 to 30. Mannum – between Morgan and Murray Bridge – is expected to peak on December 28, with grave fears held for businesses along the low-lying northeastern end of the town’s main street.

Mannum has been the focus of a levee-building operation as part of an 8km rollout of temporary military levees being installed at towns in the danger zone.

The process has been fraught in Mannum, with a huge effort underway to save the caravan park at the northeastern end of the main street. Several businesses have been told nothing can be done to save them. They include a surf shop, a bric-a-brac store, the Mannum Dock Museum and the popular nursery Down to Earth Plant Sales, which attracts gardeners from across SA with its low prices of seedlings and plants.

Tim Marshman is moving his Down to Earth Plant Sales business to higher ground. Picture: Matt Turner

Owner Tim Marshman is philosophical, being in the lucky position where his landlord has kindly agreed to waive the rent for the vacant riverside block where his nursery is located.

He is moving all his stock to his family home on higher ground at 13 Boomerang Ave and is telling his 3000-plus Facebook followers that the nursery will now operate out of his yard. “We are cashing in at the moment because so many people are coming up from Adelaide to see the river in full flow,” he said. We only open on Saturdays and Sundays but the last few weekends we have had 30 people in the nursery at any given time all day and have had to restock.”

SA Emergency Services Minister Joe Szakacs told The Weekend Australian that while a flow rate of 175 gigalitres was regarded as “most likely”, 200 gigalitres was seen as “possible” and 220 gigalitres “less likely”. “We are making preparations to respond to every scenario,” he said.