The 47-year-old was driving along Stirling Road before being caught in the flooded Spring Creek on Monday morning.
Police allege he attempted to free himself and swim to dry land, but was devastatingly swept away in the deluge.
Tragically, the man was weeks away from wedding his partner.
Police Sergeant Tim Hoffmann said officers are preparing a report for the Coroner.
"Today a mother and father lost their son, their children lost a brother, and a woman is grieving the loss of a partner she hoped to spend the rest of her life with," Hoffmann said.
The wet weather is keeping emergency services busy, rescue teams have responded to multiple calls for help in the Darling Downs since Monday.
A flood alert remains in place for locals in Dalby around the Myall Creek, where water rose to 3.6m on Wednesday.
Parts of Brisbane recorded more than 30mm of rain overnight, while evacuation orders continue for those south of the border in Lismore and Northern NSW.
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