Police say they were told the man went missing around 1.30pm on Monday near Casson Avenue at Loxton North on the River Murray.

Crews searched until last light yesterday and resumed their search this morning.

Local police along with SES crews in boats and PolAir are searching the River Murray and surrounding area for the man.

Water Operations Unit are also on scene.

Peak flows have passed the Riverland and are expected to reach Murray Bridge, Jervois and Wellington in the coming days before reaching the Lower Lakes later this month.

The Tailem Bend ferry is at risk of closure within the next four to seven days, meaning what was previously a 10-minute exercise to cross the river will turn into an 80-kilometre round trip to access the road crossing at Murray Bridge.

Closing the Tailem Bend ferry would bring the number of closed ferries along the River Murray to 11.

Ferries at Cadell and Narrung might also close by mid-January as the flood peak continues down the river.

The state government yesterday approved one-off $300 payments for thousands of low-income residents in River Murray communities forced to spend more on fuel.

-with AAP