Engineers backed by hydrologist

The engineers have been accused of moving to greater releases later than stated, creating a fictitious final report and misleading the inquiry.

Sarah Harvey

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GOING against the tide of evidence, an independent flood hydrologist has argued engineers who operated Wivenhoe Dam acted responsibly and by the book during last January's flood crisis.

Hydrologist Mark Babister was asked by the Queensland Floods Commission of Inquiry to re-examine water releases from the dam on the weekend before the Ipswich and Brisbane flooded.

"It was in accordance with the manual and responsible," Mr Babister said yesterday.

"You could possibly argue for some slight changes."

The engineers have been accused of moving to greater releases later than stated, creating a fictitious final report and misleading the inquiry.

In his eighth report for the inquiry, Mr Babister said releases greater than the ones the engineers used would have amplified the floods initially, but reduced the peaks overall.

He was also asked to model two water release strategies.

The first, G1, invokes release strategy W3 at 8am on January 8 as the engineers say they did, and ramps up releases to get a total flow at Moggill of 4000 cubic metres a second.

The second, G2, also enacts W3 on January 8, with the floodgates opened as fast as permitted by the manual, to maintain a release rate of 4000 cubic metres a second.

Mr Babister's report said the greatest flood peak reductions were achieved under G1.

He said although both scenarios would have had some benefit to downstream areas, neither would have been realistic last January because there were no grounds for such large releases.

He said the scenarios relied on releasing water and raising flood levels substantially, well before engineers knew they were in for a serious flood.

"If we didn't have the rest of rainfall, we would have actually made flooding significantly worse, worse than would have occurred probably without the dam wall. I very strongly expressed my opinion that neither were practical and highly risky," he said.