Vince Rodriguez sought damages after his sporting goods store was devastated by the massive rain event.

In a landmark decision in 2019, the NSW Supreme Court found the entities were liable for the failures of engineers operating two dams during the floods.

On Friday, it ordered Mr Rodriguez be compensated.

Seqwater will bear the brunt of the costs, paying $126,500 or 50 per cent, while Sunwater will stump up 30 per cent and the Queensland government the remaining 20 per cent.

The ruling could make way for one of Australia's largest class action payouts.

Almost 7000 people have taken legal action against the state government and its water suppliers over the 2011 Brisbane floods.

Maurice Blackburn Lawyers spokeswoman Rebecca Gilsenan said she hoped it now moved quickly to resolve the legal proceedings.

"This decision paves the way for the state government to settle this matter and pay our clients the compensation they deserve," she said in a statement.

Ms Gilsenan said she and her clients were pleased the court had rejected the state's claim it was only responsible for less than one per cent of the damage caused during the floods.

The case was heard in a NSW court because it was initiated before class actions were allowed in Queensland in 2017.

Australian Associated Press