The River Murray has been immediately closed to all non-essential activity, with South Australian Premier Peter Malinauskas warning the ban will be in place “for some time to come”.
Swimming, boating, motorised vessels and fishing activity have all been banned between the NSW-Victoria border and Wellington.
The only exception is for people working, visiting their own property, making food or fuel deliveries or responding to emergencies.
Mr Malinauskas said the “regrettable decision” had not been made lightly, but public safety was the priority.
“We’re approaching the peak … there’s a lot more water that’s going to be coming down the river over the course of the next seven days than what is currently the case, so at some point we had to draw a line in the sand on this,” he told reporters on Tuesday.
An exclusion zone of 50m was previously in place around power assets, which Mr Malinauskas said had meant some disconnections had been prevented, but the ban would allow “a degree of more flexibility”.
“By having a total ban of activity on the river, that will allow for South Australian Power Networks in conjunction with the Office of the Technical Regulator to have a bit more flexibility around which homes and businesses will be disconnected from power to prevent those disconnections,” he said.
Mr Malinauskas also said the ban would better protect the levee banks from damage.
He said authorities would seek to reopen the river as soon as possible when the peak passed.
“Normally, at this time of year we’d want the river to be full of activity from recreational users and tourist operators,” he said.
“We don’t want a situation where the river is closed for a moment too long … I don’t anticipate that will happen in early January, but certainly that will be reviewed on an ongoing basis.”
Deputy Police Commissioner Linda Williams said if people ignored the direction, they faced a fine of up to $10,000.
“We will also be using our air assets up and down the river to ensure safety, and we will have a very highly visible police presence along with marine safety teams,” she said.
Resident Julie Morris shared photographs on social media showing the view of the floods in Ponde from the top of her property.
“Wow; it’s now very real,” she wrote.
Ms Morris said her property was high enough to “escape” the worst of the floods.