South Australia is bracing for a mass emergency and widespread flood damage, with levees already breaking and the Murray not expected to see peak flood levels for the best part of a week.

Dozens of homes and two caravan parks have been evacuated in South Australia as flood levees continue to fail.

About 4000 properties across the length of the river are expected to be inundated and more than 1100 have been flooded so far.

An estimated 255 businesses and 4000 hectares of productive agricultural land will also be impacted.

The State Emergency Service has evacuated the island village of Walker Flat, east of Adelaide, after it was cut off by the deluge on Christmas morning.

It warned people not to enter the flood zone, which may be further inundated in the coming hours.

“Anyone remaining in, or entering the warning area may become isolated or flooded,” the SES said in an alert on Sunday.

“Anyone remaining in the warning area should evacuate to stay with family, friends or alternate accommodation in areas unaffected by flooding.”

Historic pub threatened

About 100km northeast, the Kingston-on-Murray Caravan Park has been evacuated after the flood levee there failed and water started flooding the property.

The historic Overland Corner Hotel, about 7km north of Kingston-on-Murray could also be inundated after a flood levee failed at the heritage-listed pub, which was built in 1859.

Upriver, the levee at the Renmark Riverbend Caravan Park also failed on Christmas morning triggering an evacuation of the property.

“There is a risk of flood waters threatening the safety of people in the park,” the SES warned.

“Park residents and visitors have been evacuated and should not re-enter. The park is closed until further notice.”

Levees are continuing to fail and two warnings are in place along South Australia’s upper and lower Murray as communities prepare for the flood peak.

SA Emergency Services Minister Joe Szakacs said the high water mark would reach Renmark on either Christmas Day or Boxing day.

The river will then peak at the town of Waikerie between December 29 and January 9, Swan Reach between January 2 and 13 and Murray Bridge between January 3 and 14.

Not the worst, but bad enough

River heights are likely to be around those experienced during the 1931 floods but still well below record levels experienced in 1956.

Earlier this week all non-essential activity including recreational boating, fishing and swimming were banned on the Murray as a safety measure.

There are exceptions to the prohibition with people requiring access to the river for work, including tourism operators or those visiting their properties able to do so.

The supply of food and other provisions will also be allowed.

Police will work to educate the community about the new rules, but those who persistently breach the ban could face a fine of up to $10,000.

-with AAP