UPDATE: The Mary River level is 10.65m, down from 10.75m about two hours earlier, but a peak of 11m is still expected, Fraser Coast Mayor Gerard O'Connell says.

He said Gympie's floodwater was expected to reach Maryborough later on Tuesday and the city might be flood-affected for a further 24-36 hours.

Cr O'Connell said although the 11m peak was expected about 6pm on Monday night, the rise of the river had slowed considerably.

He believed that even if the river reached a peak of 11m, no more businesses, than were already flooded, would be significantly affected.

Emergency response groups will meet on Tuesday morning to assess Maryborough's flood situation.

A Fraser Coast Disaster Co-ordination Centre spokesman said the rise or fall of the floodwaters was dependent on what happened in Gympie overnight, and an action plan would be formed on that basis in the next few hours.

Cr O'Connell confirmed that water breached the levee in the central business district late on Monday night but said it had done it's job by allowing more time for businesses to prepare for the flood.

"It held really well," he said.

"I think it's done it's job - it gave us a lot of breathing space."

EARLIER: Despite sunshine and blue skies, Maryborough's central business district is flooded and the levee is believed to have broken.

The Mary River level is 10.7m and rising slowly, the Fraser Coast Disaster Coordination Centre said in an update at 5.45am.

"Still working to peak of 11m," the centre said.

The Dick Smith shop in Adelaide St is flooded and water is lapping at the feet of the Chronicle building in Bazaar St but the office is still dry inside.

A patch of thick oil has been spotted in the floodwaters.