Premier backs 'tough calls' over flooding

Leaving some Murray properties and businesses in South Australia at the mercy of the rising river are "tough calls", Premier Peter Malinauskas says.

But the premier believes the state government has done as much as it can to protect as many properties as possible, and to provide financial and other assistance as flood waters continue to surge across the border.

Up to 4000 shacks, homes and businesses are expected to be inundated in SA as flows down the Murray rise to about 175 gigalitres a day in early December before surging even higher around Christmas.

"I'm very confident in the fact that the government has done as much as we reasonably can in difficult circumstances," Mr Malinauskas said on Monday.

"But I'm also very conscious of the fact that no matter how much we do there are going to be somewhere around 3500 to 4000 properties that are going to be inundated.

"That means real people being affected in a substantial way."

"And when you make tough decisions to literally protect some places and acknowledge you can't protect others, these are big judgment calls."

The flooding down the Murray is expected to be the worst since the 1970s. Areas most at risk include Renmark, near the Victorian border, and Mannum, east of Adelaide, where a levee is being built that will leave some businesses and homes unprotected.

The levee at Renmark has been upgraded to better protect the low-lying parts of the town, including the local hospital.

From Tuesday, flood-affected Riverland residents will be able to seek government support and assistance from a one-stop shop with the first Emergency Relief Centre to open in Berri.

The government last week announced a $51.6 million assistance package, including support for tourism and other businesses, and provide assistance to homeowners.

It includes $9.3 million for levee works, $4.8 million for sandbags and other defences, rental assistance for families, grants of up to $20,000 for businesses forced to close, and grants to buy generators for properties set to lose power.

Individuals will be able to apply for $400 personal hardships grants, with families to receive $1000.

State Emergency Service chief officer Chris Beattie said work was continuing along the length of the Murray to protect as many properties as possible.

But he said some had already been inundated and 65 roads had now been closed, potentially isolating small communities.

About 700 properties have had their power cut with another 700 to suffer the same fate this week.