The operators of Queensland's Wivenhoe Dam will continue their defence against a class action when a trial over the 2011 floods resumes in Sydney on Monday.

Maurice Blackburn is representing more than 6000 individuals and businesses impacted by the deluge who claim the dam was operated negligently when huge volumes of water were released in January that year.

Last week, lawyers for Seqwater rebuffed claims the flood engineers should have taken rainfall forecasts into account when making operational decisions, arguing the Bureau of Meteorology itself warns the reliability of predictions is not always sufficient to do so.

Seqwater’s barrister Brian O’Donnell QC said it would be an “extreme” method to pre-release water before rain had even fallen.

The defendant has also mounted a “contributory negligence” argument, contending victims should have done more to protect their properties or known they had built or leased on land that flooded decades before.

Seqwater claims the engineers rightfully believed they were not able to empty the dam below the so-called full supply level for flood mitigation purposes, however the plaintiffs say if more storage space had been made available the impact of downstream flooding would’ve been lessened.

The trial, which is being run in the NSW Supreme Court because Queensland didn’t have a class action regime when it was filed, continues on Monday.