POLICE have told residents in low-lying areas of Strathpine and Caboolture to evacuate immediately as the flood alert hits the Brisbane area.

"The flood levels are expected to be greater than the 1974 floods. Do not stay in your homes please leave immediately," the alert said.

"Cars should be moved from low-lying areas."

Ipswich should also prepare to evacuate, the city's mayor says.

Mayor Paul Pisasale said residents in low-lying areas and near the Bremer River should get out, with rivers due to peak overnight.

"I'm told by the experts we are likely to see levels similar to the dreadful 1974 floods," Mr Pisasale said today.

"At this stage the Bremer River in Ipswich is expected to reach 17.2 metres at between 11pm (AEST) tonight and 1am tomorrow, which is nearly two metres below the 1974 level."

He said river heights were expected to remain high for one or two days.

"Residents in flood-prone areas should make immediate plans to self-evacuate, and where possible stay with relatives and friends," he said.

The mayor said evacuation centres were being identified today, and residents would be told where to go as soon as possible.

A suburb-by-suburb street listing was also being prepared to warn residents and extra staff called in to man the council's call centre.

"Again I ask all residents to keep listening to radio and TV broadcasts and to keep fully informed of flood levels," Mr Pisasale said.

Police say the Ipswich Motorway, running to the west of Brisbane, may be closed before 1.30pm (AEST) due to flooding in both directions.

Modelling is being conducted to see what floodwaters in the Brisbane and Bremer rivers will mean for Ipswich and Brisbane.

The Brisbane City Council has warned about 200 properties could be flooded, most in the areas of Rocklea, Albion, Milton and Auchenflower.

People in West End, in inner-city Brisbane, have already been asked to move to higher ground.

Authorities say Wivenhoe Dam, built partly as a flood mitigation strategy after the 1974 flood, was all that stood in the way of a repeat of the devastating event.

At least 6700 homes were partially or totally flooded in the Brisbane metropolitan area and some homes were completely washed away in the 1974 flood.

At Ipswich, 1800 homes and businesses were totally or partially inundated and 41 homes were washed away.

Fourteen people died and more than 300 were injured.

Originally published as Evacuations in Strathpine, Caboolture