Two members of the public raised the alarm after the 59-year-old from Carseldine came into trouble crossing Cabbage Tree Creek Road in Fitzgibbon on Sunday afternoon.
The bystanders conducted CPR and despite the efforts of paramedics, the man died at the scene.
By Monday several people were missing in floodwater: a man who fell in the Brisbane River last week and a 76-year-old man in Glen Esk, whose vehicle was seen in floodwater in the Brisbane Valley Highway.
Authorities warned at least one further major peak was still expected in Brisbane.
“What we’re seeing is the system pushing south to Logan, the Gold Coast and seeing some tragedies unfolding in NSW,” Queensland Premier Annastacia Palaszczuk said.
“We’ve been through a lot together. We’ve been through a pandemic of two years and yet another flood.
“No one has seen this amount of rain in such a short time in our entire south-east catchment zone.”
The Brisbane River peaked at 3.85 metres on Monday, just under the 2011 flood peak of 4.46 metres.
More than 1000 schools have been closed and most public transport in Brisbane was cancelled.
There were 2200 requests for assistance and 113 water rescues around the Gold Coast, Beenleigh and Brisbane areas.
The Mount Crosby water treatment plan was running again at a reduced capacity after it was down on Sunday and residents were urged to reduce water usage.
Despite the rain stopping for the first time in days around Brisbane, the saturated catchments are still feeding into creeks, brooks and the Brisbane River.
The Bureau of Meteorology predicted major flood levels to rise in Brisbane as well as Ipswich, which peaked about 16.7 metres on Monday morning.
The bureau’s Diana Eadie said the most intense rain had eased in large parts of the south-east, but the threat remained for the Scenic Rim and Gold Coast.
“There’s still a lot of water around [the Brisbane and Bremer rivers] we could see a secondary peak this evening at around about 8pm.”
Rainfall totals between 400 and 800 millimetres have been recorded across the catchment over the past four days, causing widespread and significant flooding across the catchment.
In a later press conference with Prime Minister Scott Morrison, Brisbane lord mayor Adrian Schrinner reiterated the need to stay vigilant ahead of a further 3.5-metre peak at the evening high tide about 8pm.
“My key message to the people of Brisbane is that we are not out of the woods yet,” Cr Schrinner said. “We have been through worse than this before. [But] we know that there are also many parts of Brisbane that weren’t affected in previous floods that have been affected this time.”
He said almost 300 people were being accommodated in the city’s two evacuation centres.
The “mud army” of 2011 would be dispatched to help with clean-up efforts once the flooding threat subsided.
Disaster assistance has been extended to councils in Brisbane, Moreton Bay, Redland, Scenic Rim, Somerset, South Burnett and the Southern Downs.