11 April 2011

Flood Inquiry: Dam operator defends flood actions


ONE of the engineers in charge of the Wivenhoe Dam during this year's devastating floods has hit out at accusations he did a poor job.

Wivenhoe Dam.

ONE of the engineers in charge of the Wivenhoe Dam during this year's devastating floods has hit out at accusations he did a poor job.

Senior flood operations engineer for Wivenhoe Dam, Robert Ayre, today made his submission to Queensland's Floods Commission of Inquiry, which begins hearings in Brisbane on Monday.

He is one of four engineers responsible for the direction of flood operations for Wivenhoe and ensuring it is operated by the manual.

A trial by media erupted following the January floods with a number of newspapers accusing dam operators of contributing to the devastation in Brisbane when the flood peaked on Thursday January 13.

There were claims operators should have released more water on the preceding Saturday to reduce affects.

Furthermore, it had been claimed operators not only panicked two days before the peak by releasing water in quick succession, but the size of releases almost breached the dam's manual.

Mr Ayre said he was happy with the amount of water released on the Saturday because there was a significant amount of flood storage available in the dam to deal with increased rainfalls.

Meanwhile, he said if there were increased releases, it could have adversely affected people living downstream.

"Excess of those made would have resulted in the inundation of Fernvale Bridge and Mount Crosby Weir Bridge, and in my view, this would not have been consistent with the requirement of the Wivenhoe and Somerset Manual," he said in the statement.

"And releases which approached 1600m3/s would likely have resulted in minor flood damage in low lying areas in Brisbane."

He also rejected criticism that massive releases of water on the Tuesday produced most of the flooding in the Brisbane River and almost breached the manual, which stated outflows must not breach the inflows.

Gate operations immediately commenced after heavy rain on Tuesday morning, with 14 directives issued in just over 12 hours.

"These directives preserved the structural safety of the dam," he said.

"This approach also allows the response of the dam to be assessed and gate operations to be refined in response to any changes in the lake levels.

"Release rates did not exceed inflow rates until the peak of the dam had passed and the water had started to recede."

Mr Ayre, who has 28 years' experience in water engineering projects, highlighted in his submission a problem with measuring inflows to the dam.

He said there were no catchment gauges directly on Lake Wivenhoe and that affected the modelling for the inflows.

"The real time modelling undertaken with the actual data does not reproduce or account for the rapid rise in lake level recorded," he said.

"There is a large, unmonitored area where there are no rainfall gauges which covers a large component of Lake Wivenhoe."

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COMMENT: Blame the manual and all will be well - that's what Robert Ayre seems to be saying to the people of Southeast Queensland.  Did the manual cover ever possibility and eventuality which might arise in the course of a heavy rainfall dam?  If not, why not? Mr Ayre says the lack of catchment gauges on Lake Wivenhoe affected modelling of the inflows.  On how many occasions, did he raise this issue with his superiors?  Will he release any documentation which shows that he officially raised his concerns over this issue and what his superior officers did about it?

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