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| Wivenhoe Dam |
A briefing note, drawn up for Water Minister Stephen Robertson by Water Grid chief Barry Dennien for an emergency Cabinet meeting on January 17, warned that floods like the one being experienced could "overflow the dam's storage compartment", with catastrophic results.
"Should this occur, the dam would fail and the resulting damage and loss of life would be at least 100 to 1000 times greater than that currently being experienced," Mr Dennien wrote.
But this was at odds with the facts known at the time and with published information about the structure of the dam.
Dam levels had already peaked on January 11 at a level almost 1m lower than the point at which safety features designed to prevent a dam collapse begin to come into play.
The first of these are "fuse plugs", safety valves built in to an earth embankment that erode to release water when the dam reaches a certain height.
These were added in 2005 as part of a $70 million upgrade of the dam, intended to make it withstand the biggest imaginable flood, thought likely to occur only once every 100,000 years.
The first fuse plug is designed to be needed only in an "extreme" 1-in-6000-year flood.
By contrast, the official Seqwater report into the floods describes a much smaller event, likely to occur once in every 100-to-200 years.
Mr Robertson told the flood inquiry this month that no decisions had been made on the basis of the briefing note at the Cabinet meeting.
But Ms Bligh made a series of public statements during and after the flooding in Brisbane and Ipswich in which she highlighted the dangers of the fuse plugs being triggered.
The briefing note, approved by John Bradley, then director-general of the Department of Environment and Resource Management and now Ms Bligh's top adviser, was requested by Mr Robertson and drafted over the weekend of January 15 and 16.
20.2.12
