CLASS action will begin in the NSW Supreme Court today into the Queensland floods of 2011.

Maurice Blackburn Lawyers are representing more than 6000 people and businesses who allege dam operators failed to follow their manuals, causing unnecessary disaster across the state.

The floods in early 2011 caused hundreds of millions of dollars in damage in Brisbane and southeast Queensland.

"This trial will demonstrate that the dam operators did not operate the dam during the flood event in accordance with the operation manual that they themselves wrote, and the consequence of that was unnecessary devastation across southeast Queensland," said Maurice Blackburn Lawyers' Rebecca Gilsenan.