Qld floods probe 'not Fitzgerald inquiry'

Queensland's flood inquiry never set out to be a "Fitzgerald" style investigation, floods commissioner Cate Holmes says.

Justice Holmes ended Saturday's hearings defending the work of the inquiry and explaining why it had missed crucial evidence that sheds doubt on whether Wivenhoe dam engineers were telling the truth.

She said she heard suggestions that the inquiry could not be trusted because it had to reconvene extra hearings after a journalist discovered conflicting dam accounts.

Justice Holmes said it was not the commission's job to seek out culprits like the 1980s Fitzgerald Inquiry into police corruption.

"This is not a Fitzgerald inquiry," Justice Holmes said.

"My task as set out in the terms of reference was not to search out culprits but to make recommendations to improve preparation and planning for flood threats..."

She said the commission could not have reviewed every written and oral statement but she was "grateful" for the work of the journalist who uncovered contradictory evidence.

The extra sittings are delving into allegations four Wivenhoe dam engineers used the wrong strategies, compounding the devastating floods that hit Brisbane, Ipswich and surrounds in January last year.

It is also investigating allegations the engineers colluded to cover up their mistakes in a final report on the operation of the dam during the crucial days leading up to the floods.

Seqwater's Jim Pruss, who project-managed the engineers' final report, was grilled over why two key documents which contradict the engineers' evidence were not included in the report released in March last year.

The missing documents indicate water releases from the dam were operating at lower levels than necessary to protect urban areas from inundation.

Mr Pruss, the Seqwater water-delivery executive general manager, told the inquiry he believed the omissions were an accident.

"Thinking about the logistics those guys had to go through to put it together in a short period of time, it's possible and likely that it was an accident," Mr Pruss said.

"The report was 1300-odd pages long. There was lots of data to pull together."

In response to a question from Peter Callaghan, counsel assisting the commission, Mr Pruss said he had no reason to doubt the engineers.

"My mind was at ease because the engineers had a detail-checking mechanism of the data and the words," Mr Pruss said.

"We also had the experts in there who could ask them whatever they wanted."

He said that was all the checks and balances he believed were necessary.

Saturday is expected to be the last sitting day of the inquiry.

A final report on the findings is scheduled for March 16.