A man has died after being caught in floodwaters near Toowoomba and further south another man is missing as a slow-moving trough is predicted to continue dumping heavy rain on Brisbane and the Gold Coast overnight.
The Bureau of Meteorology said the system was expected to drop more than 100 millimetres of rain on the Gold Coast on Monday and flash flooding was possible as the system moved south on Tuesday.
An emergency alert was issued for Dalby in the Western Downs on Monday afternoon, with Myall Creek expected to exceed the Major Flood Level of 3.5 metres late on Monday night.
Residents with properties in low-lying areas near Dalby were being urged to warn their neighbours, secure their belongings and prepare to move to higher ground immediately.
Queensland Fire and Emergency Services (QFES) conducted nine swiftwater rescues from Sunday night to Monday afternoon across the Toowoomba region and received more than 80 requests for help since Sunday afternoon.
Shortly before 5:00am on Monday, rescue crews were called to an incident near Kingsthorpe, north-west of Toowoomba, where a vehicle was reported in floodwaters.
Police said a woman was rescued and taken to hospital in a stable condition for treatment, but a man was found dead in the ute. A number of dogs also died.
QFES zone commander Warren Buckley said crews faced challenging conditions at Kingsthorpe.
"It is quite turbulent, some of the water that's coming down through there," Mr Buckley said.
He said crews were also called to three other rescues for people driving through floodwaters.
QFES also dispatched a swiftwater rescue crew to Macalister, south of Toowoomba, where one person was reported trapped in a car in floodwaters.
On Monday afternoon, four crews were sent to Commodity Court in Dalby where a truck driver was retrieved from his vehicle.
Police are also coordinating an extensive search and rescue operation at North Branch in the Southern Downs, for a man believed to be missing in floodwaters.
Just after 6:00am on Monday, emergency services were called to reports two vehicles had become stuck in floodwaters at a crossing with Spring Creek near Stirling Road.
A woman, the sole occupant of one of the vehicles, was assisted to safety by members of the public.
Police said initial investigations indicate a man in his 40s got out of the other vehicle, of which he was the sole occupant, and was swept away in the flood.
Police, swiftwater rescue crews and the RACQ Lifeflight Rescue helicopter are searching the area.
"It's frustrating that we're losing people, good people from our communities, from doing things such as driving into floodwaters," police Acting Inspector Kim Hill said.
The Bureau of Meteorology (BOM) expects a slow-moving trough to dump more heavy rainfall on parts of the south-east on Tuesday, four weeks after heavy downpours caused significant flooding in the region.
Emergency services were called to a driver stuck in floodwaters on Greenmount-Etonvale Road near Toowoomba shortly before 5:00am on Monday.
Authorities said the driver was on the roof of their car and crews were able to rescue them.
QFES State Operations Commander Cheryl-Lee Fitzgerald said the rescues were a reminder of how quickly and dangerous situations can get.
"Stay aware of the risk … stay well away from floodwaters," she said.
More dam releases, flash flooding possible
Seqwater said flood releases began at Wivenhoe Dam, 80 kilometres north of Brisbane, late on Monday.
Somerset Dam, which feeds into Wivenhoe Dam began releasing water on Monday morning.
The bulk water supply authority said further releases might be necessary at North Pine Dam, north of Brisbane.
The rainfall has also led 19 ungated dams in the south-east to spill.
BOM forecaster David Grant said bursts of heavy rain totalling up to 200mm from a slow-moving coastal trough will fall across south-east Queensland over the next 12 to 24 hours before the system moves south to New South Wales.
"This event is very different to the last one," Mr Grant said.
"There is a risk of local intense rainfall and with that given there's a lot of wet catchments around south-east Queensland.
"There is going to be an increased risk of localised dangerous and life-threatening flash flooding and given the weight catchments also the risk of landslides during the course of this event.
"Although our rainfall totals won't reach the magnitudes of what we did see in the last event, we have to be mindful that our catchments very wet from that last event and, therefore, won't take as much rainfall to see very rapid responses in a lot of our creeks and streams.
"Hence [this is] why we've got our flood watch out and why there's a lot of risk around our creeks."
Conditions in Queensland are expected to ease from Wednesday.
Flood watches put in place
The BOM has a Major Flood Warning in place for Myall Creek, with a Moderate Flood Warning for the Bokhara River and Minor Flood Warning for the Condamine River and the Paroo River.
An emergency alert was issued by the Western Downs Regional Council on Monday morning.
The BOM warned that flooding had peaked along Myall Creek at Clydesdale and was expected to continue downstream to Dalby on Monday night.
An Initial Minor Flood Warning has also been issued for the MacIntyre Brook catchment, following heavy rainfall of 20-60 millimetres over the catchment.
There is also an Initial Minor Flood Warning for the Upper Dawson River.
More rain to hit northern NSW
Mr Grant said the coastal trough has been moving south and that, unfortunately, there would be an increase in rainfall across the Lismore area.
"We do have severe weather warnings covering the area and also we do have a number of flood watches that cover many of the areas around north and north-eastern New South Wales at the moment,'' he said.
Mr Grant said rain would persist over northern NSW "over the next few days".
