A possible levee failure has prompted the order from the South Australian State Emergency Service leading to the relocation of six people from the Riverbend Caravan Park, which is now closed.
SASES Chief Officer Chris Beattie said engineers on Wednesday assessed the private levee built at the park and identified "a number of significant defects which puts the levee at risk of failure".
"If the levee fails, there is a risk of flooding which may impact anyone in the park behind the levee," he said.
Mr Beattie said the SASES and the Department for Environment and Water were assessing private levees along the river and further evacuation orders could be issued.
With the floods looming, authorities have doorknocked 4800 properties to ensure everyone likely to be impacted understands what is coming their way.
That has identified about 260 households that will need help with somewhere to stay.
Premier Peter Malinauskas on Tuesday said $1.2 million would be allocated to book up to 500 beds across local towns as a last resort for those forced from their homes.
He said it was hoped as many people as possible would first try to stay with family or friends, given they may be unable to return to their properties for some time.
SA Health has also boosted mental health services and the rollout of the Japanese encephalitis virus vaccine in flood-affected communities.
SA Flood Mental Health Response will provide increased specialist and early intervention mental health services to Riverland communities in a bid to minimise the long-term impact of the expected flooding.
Up to 4000 properties in SA are expected to be inundated, 450 of which are considered permanent residences.
The expanded Japanese encephalitis vaccine program will protect emergency services workers during the crisis and home owners when they return to clean up as waters recede.
The first peak in the river level is tipped to reach Renmark, near the Victorian border, about December 14.
The peak is expected to reach Mannum, east of Adelaide - where levee strengthening and construction efforts are in full swing - around December 27
After a brief settling of water levels, a second peak is forecast to reach the SA border towards the end of the year..
"The water is coming. There are many homes and properties that simply cannot be protected from that," Mr Malinauskas said.
The SA government previously announced a $51.6 million assistance package, including support for tourism and other businesses, as well as direct emergency payments to homeowners.
The federal government has also provided the disaster recovery allowance to people across nine SA districts.
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