One woman died after being swept away in her car near Brisbane as almost eight inches of rain fell in a few hours.

Thousands of homes were without power, having just recovered from the first storm, which struck on Sunday.

Brisbane resident Dave Gilbank said he "woke up, looked around ... and found that my bed was floating in about four feet of water".

Queensland state Premier Anna Bligh invoked special powers granted during natural disasters to co-ordinate rescue efforts.

Troops were deployed while neighbours and volunteers pitched in elsewhere to help clean up.

Creeks and drains overflowed into streets and gardens, collapsing bridges, flooding roads and sweeping away everything from toys to cars in the worst flooding in decades, officials said.

A pregnant woman was rescued while on her way to the hospital to give birth when her car became trapped between two overflowing streams.

Part of the same area of the state was declared a disaster zone earlier this week after a storm officials dubbed a mini-cyclone struck on Sunday, tearing roofs off houses, cutting electricity and causing other damage. Troops and other emergency crews were still working in the disaster area when the second storm stuck.