An emergency warning is in place for a small Murray River community east of Adelaide with residents urged to evacuate as river levels surge.

The South Australian State Emergency Service said properties at Walker Flat would likely become isolated on Thursday.

“Regardless of your property’s ability to withstand flood impacts, there is a chance you may also become flooded,” the SES told residents.

“You need to evacuate now.”

A watch-and-act message is also in place for a 40-kilometres stretch of the Murray, taking in the communities of Caurnamont, Purnong and Bowhill.

The alert follows a rapid rise in water levels.

Up to 4000 properties in SA are forecast to be inundated by the water surging down the Murray, with more than 450 of those considered permanent residences.

The first peak in the river level reached Renmark, near the Victorian border, this week.

The peak is expected to reach Mannum, east of Adelaide about December 27.

After a brief settling of water levels, a second and higher peak is forecast to reach the SA border towards the end of the year.

That could result in daily flows of up to 220 gigalitres.

The SA government had secured more than 22,000 overnight beds for people forced from their homes. It will also construct 16 self-contained huts at the Riverland Exhibition Centre near Barmera, with the same site providing space for up to 200 caravans.

The state government has also taken a lease over a fully accessible site suitable for people with mobility issues and care needs, should it be required.

Levee construction along the river is nearing completion. The work is expected to finish in towns such as Mannum, Berri and Loxton this week.

Most ferry services across the river have closed or been moved to higher ground.

The SA government has provided a $51.6 million assistance package, including support for tourism and other businesses, as well as direct emergency payments to homeowners.

– AAP