The South Australian government is now expecting the current River Murray flood emergency to be the worst since 1956, with more than 1,100 properties already inundated.
The government estimates the floodwater peak is due in Renmark around the end of December at a level between 190 and 220 gigalitres a day.
The height of the river is in excess of major flooding in 1931 — which is also higher than the 1974 flood — but not as significant as the 1956 event.
More than 1,100 properties have been inundated so far with a total of 4,000 expected to go under by the end of the month, including 255 businesses.
A flood watch and act message has been issued Thursday afternoon for Mannum and Mypolonga, as well as the smaller localities of Younghusband, Caloote, Pompoota, Caurnamont, Purnong and Bowhill.
The State Emergency Service says people in low-lying areas in these locations are at a high risk of flooding.
"The anticipated peak timeline continues to be in that Christmas-New Year period for the upper Riverland communities, and then of course it progresses as time evolves," Premier Peter Malinauskas said.
“We are on the current data that we have available seeing that the 1931 flood levels will be more comparable to this event than the 1974 levels, which were lower than the '31 levels. But all the forecasts continue to show that it will be well below the 1956 levels.
“Naturally we continue to monitor all this very closely including ongoing events that happen further in the catchment area in terms of rainfalls … because of course we don’t know what weather events will occur upstream in the catchment, whether or not there's a tropical cyclone during the course of the summer."
Mr Malinauskas said the government was in talks with the Commonwealth about securing Australian Defence Force support, adding that there was a strong need for swift-water rescue teams.
While crucial town levees are holding, the State Emergency Service (SES) has responded to a "number of identified levee defects and failures" including near Renmark, Barmera, Mannum and Kingston-on-Murray, and there has also been been a breach upstream of Lake Victoria in the south-west NSW.
Walker Flat residents respond to warning
On Wednesday night, the SES issued an emergency evacuation warning for the community of Walker Flat, advising that properties could be inundated or cut off, as water floods Angas Valley Road and Rob Loxton Road.
"We anticipate over the next two to three days that we'll see significant rises in the river where we'll have flooding into the properties and also the access roads will be compromised," SES chief officer Chris Beattie said.
"It's really important for people living in those areas that they initiate their plans now."
Walker Flat resident Tracey Arnold, who has taken refuge in Adelaide, left the area on Wednesday night — and said the water had already reached her yard.
"In my property, it was halfway up my backyard … I live on a road that's only got one entrance so it came across the causeway," she told ABC Radio Adelaide.
Another resident, Carlene Grove, also made the decision to leave, and said the water was now just centimetres from her property.
"Friends came and helped … and everybody that went past stopped to see if we were okay – everybody," she said.
"They were so good, really good. It's nice to know that people care when the time comes."
The Walker Flat ferry was expected to shut on Thursday night and, while it remains open to residents who need to be evacuated from the area, is now closed to most other traffic.
Preparations ongoing in Mannum
SES regional commander Leanne Schmidt said the speed of the water level rises meant the town of Mannum — which has a population of about 4,000 — could be impacted sooner than initially thought.
"Some of the water rises and the volume of water has been a bit of a surprise in some areas, we saw it happen at Blanchetown the other night and then at Walker Flat," she said.
"One of the main access roads into the area was being undermined and was in danger of collapsing."
Preparations in Mannum have been ongoing for weeks, and include sandbagging and levee works in the main street to construct what locals are calling the "great wall of Mannum".
The Department for Environment and Water's Ben Bruce said while the peak was still days away, the end of the deluge was in sight.
He said lower rainfall forecasts over the next week and increased irrigation demand would help reduce the volume of water in the river system.
"We are now starting to see a lot of the tributaries in Victoria starting to recede, we've seen over the last few weeks Hume [Dam] releases drop back to around 10 to 12 gigalitres which is down from the peak of 90," he said.
"The system is starting to contract, it means we can start to see an end to this event in sight.
"In terms of the peak, it's currently travelling between Euston which is just downstream from the Murrumbidgee River intersection and Mildura, and we still expect … it will arrive in our state around Christmas."
Nervous wait on both sides of levee
Mid Murray Council mayor Simone Bailey said 250 kilometres of roads in her council area were expected to be impacted by floodwaters.
"There's mixed concern, there's anxiety, there's lots of feelings going around – but the thing that I see the most is the community support for each other," she said.
"When somebody puts their hand up and needs some help, that help's there."
In Mannum, local business owners are already shutting up shop.
"When we found out that the river was going to experience a significant high event, we undertook our own works to sort of prepare to trade out for as long as possible," said Brad Harper, manager of the 122-year-old Pretoria Hotel.
"Works will need to progress on the levee in the main street, which unfortunately means that we will have to close our doors for a little bit."
Houseboat operator Margaret Claassen said that, from her vantage point, she could see "just one big pond of water at the moment".
"It's quite amazing to see how quickly it's come up over the past couple of days," she said.
The Premier said while communities were well prepared, "we haven't seen anything like this in South Australia for 50 years".
"We've done all the preparation that we reasonably can but … there is clearly a degree of anxiety on the ground about the fact that there are people who are going to be affected by this, notwithstanding the [Mannum] levee works," Mr Malinauskas said.
"There are some people who are on the protected side of the levee and there are some people on the unprotected side of the levee and it's a very harsh example of the tough decisions that have to be made.
"I feel for those people on the unprotected side who are going to have their lives impacted quite significantly, whether they be business owners or residents."
