Breaking News : Boy's death takes flood toll to 10

Ipswich Mayor Paul Pisasale says the boy drowned during an attempt to rescue his family at Marburg, about 60 kilometres west of Brisbane.

"Very sad day for Ipswich. We just found out that a four-year-old boy has fallen out of a boat and they've just found the body," he said.

"So it's a very, very sad day for Ipswich and our hearts and prayers are with the family."

Authorities still hold grave concerns for more than a dozen of the 78 people still missing after unprecedented flash floods tore through southern Queensland late yesterday.

There are serious concerns for 18 of those people.

A raging torrent of water swept through Toowoomba and the Lockyer Valley, and heavy rain today has again pushed creeks to major flood levels.

Premier Anna Bligh says the number of missing people has been revised up from 59.

"Clearly as we get more information from families who are looking for their loved ones these numbers are going to fluctuate, but we now have 78 people unaccounted for," she said.

"We have 10 deaths and we have at least 18 people for who we have very grave concerns for their safety."

The wall of water is making its way to Brisbane, where rain and storms are lashing the city and the biggest flood since 1974 is expected to arrive in the coming days.

Many towns were either badly damaged or wiped out by flash flooding. Homes were knocked from their footings and cars were washed away.

There has been little progress in the search and rescue operation as police, the SES and fire crews have been battling bad weather.

Deputy Police Commissioner Ian Stewart says police are daunted by the scale of the disaster in the Lockyer Valley.

"Certainly Grantham is one of the focus, but the other one is the Murphy's Creek and Withcott area," he said.

"That's the other area we're having difficulty getting into, and it's going to take us a long time today to get to every one of those areas.

"I mean, the sheer scale of this operation is quite daunting when you look at the number of places and creeks that have been affected."

He says bad weather is hampering search and rescue operations.