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174876
Tue, 04/12/2011 - 13:38
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http://m.oananews.org//node/174876
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Brisbane dam engineer defends flood strategy
SYDNEY (AAP) - 12.04.2011 - The senior engineer operating Brisbane's Wivenhoe Dam during January's floods in Queensland has defended his decision not to accelerate sooner to the highest crisis management strategy.
Robert Ayre on Tuesday continued his evidence to the Queensland Floods Commission of Inquiry, which is examining the role of dam releases in the flooding of more than 14,000 homes in Brisbane on January 13.
The dam's manual sets out a flow chart of strategies for its engineers to adopt in floods.
Mr Ayre, the most senior of four men who controlled the dam during the disaster, was questioned at length on how and when they decided to adopt strategy W4, which puts the structural safety of the dam ahead of saving homes from flooding.
He had told the inquiry on Monday they based the decision on models that banked on no further rain, rather than more volatile models that factored in forecast rain.
But on Tuesday he agreed with counsel assisting the inquiry, Peter Callaghan, that based on forecast rain models W4 would have been adopted 36 hours sooner, giving them more time to release the dam's water.
"Our considerations at that point were we don't like to unnecessarily cause property damage, and if we can avoid it we will," Mr Ayre said.
The engineers moved to W4 at 8am on January 11 when the conditions had been met five hours earlier on the engineers' preferred method, or even earlier - at 8pm on January 9 - using forecast rain models, Mr Callaghan said.
Mr Ayre explained that forecast rain wasn't used in decision-making because it was not guaranteed.
"There is a very high risk of making releases that will either inundate bridges prematurely or inundate properties needlessly," he said.
Mr Ayre also rebuffed commentary in the media by independent engineer Michael O'Brien, who claims the dam engineers could have avoided the floods if they had released more water sooner.
"Certainly the peak may have been lower ... however, the overall combination of the downstream tributaries, with the releases from Wivenhoe Dam, would still have resulted in flood levels at the (Brisbane CBD) Port Office gauge which were above major flood levels," he said.
The inquiry also heard that Mr Ayre emailed his colleagues on January 14, saying they needed to form a "consolidated view" of the events of the flood.
The engineer denied this was to conceal information from the public or the media, but rather to give a "complete picture" of events in the flood control centre.
Meanwhile, Queensland Premier Anna Bligh says briefing notes of Water Utilities Minister Stephen Robertson, being withheld from the inquiry due to parliamentary privilege, are not of concern to the government.
The government will move to have the briefing notes released when parliament resumes in two weeks' time, she says.
The inquiry, before Justice Catherine Holmes, continues on Wednesday.
Robert Ayre on Tuesday continued his evidence to the Queensland Floods Commission of Inquiry, which is examining the role of dam releases in the flooding of more than 14,000 homes in Brisbane on January 13.
The dam's manual sets out a flow chart of strategies for its engineers to adopt in floods.
Mr Ayre, the most senior of four men who controlled the dam during the disaster, was questioned at length on how and when they decided to adopt strategy W4, which puts the structural safety of the dam ahead of saving homes from flooding.
He had told the inquiry on Monday they based the decision on models that banked on no further rain, rather than more volatile models that factored in forecast rain.
But on Tuesday he agreed with counsel assisting the inquiry, Peter Callaghan, that based on forecast rain models W4 would have been adopted 36 hours sooner, giving them more time to release the dam's water.
"Our considerations at that point were we don't like to unnecessarily cause property damage, and if we can avoid it we will," Mr Ayre said.
The engineers moved to W4 at 8am on January 11 when the conditions had been met five hours earlier on the engineers' preferred method, or even earlier - at 8pm on January 9 - using forecast rain models, Mr Callaghan said.
Mr Ayre explained that forecast rain wasn't used in decision-making because it was not guaranteed.
"There is a very high risk of making releases that will either inundate bridges prematurely or inundate properties needlessly," he said.
Mr Ayre also rebuffed commentary in the media by independent engineer Michael O'Brien, who claims the dam engineers could have avoided the floods if they had released more water sooner.
"Certainly the peak may have been lower ... however, the overall combination of the downstream tributaries, with the releases from Wivenhoe Dam, would still have resulted in flood levels at the (Brisbane CBD) Port Office gauge which were above major flood levels," he said.
The inquiry also heard that Mr Ayre emailed his colleagues on January 14, saying they needed to form a "consolidated view" of the events of the flood.
The engineer denied this was to conceal information from the public or the media, but rather to give a "complete picture" of events in the flood control centre.
Meanwhile, Queensland Premier Anna Bligh says briefing notes of Water Utilities Minister Stephen Robertson, being withheld from the inquiry due to parliamentary privilege, are not of concern to the government.
The government will move to have the briefing notes released when parliament resumes in two weeks' time, she says.
The inquiry, before Justice Catherine Holmes, continues on Wednesday.
