Sadly ...I doubt one week ahead is anywhere near enough!
If there was no dam in place the properties would have flooded. As was the case in 1974.
Having a dam there was meant to regulate potential & likely floods.
An enduring spring/summer monsoon in 2010, meant there was a 100% runoff from the Brisbane River's entire catchment, an area the size of West Germany (I believe?), so if they had emptied Wivenhoe dam in Oct thru' Dec 2016 completely, they may have had hope of containing the January 2011 flood level maximum.
As it was planned for
But, as was the case, SEQ already had a full dam - by mid December 2011, rather than an empty one.
Having a full dam by mid December, meant that when the flood rains came in early January, the dam was already full at the outset, and so the operators were forced to release not only the normal flood, but the full reservoir of water built up in the earlier spring rains too.
The Wivenhoe dam is largely a rock & earth filled embankment dam. The operators cannot risk allowing the water to flow over the top, of the dam, which it threatened to do, for fear of the entire wall collapsing, allowing a full dam's containment to flow down the Brisbane valley in a short few hours! That doubtless was the most extreme worst case, and a situation that would have been a catastrophe undoubtedly some many, many times worse.
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The back story:-
Brisbane had just suffered a long protracted drought of several long years. Plans to remedy this on an enduring basis, with an addition supply to Wivenhoe from the Mary river/ ex Maryborough had been quashed by the Greens (through the Labor's agency). Peter Garrett made the decision at commonwealth level. The pobblebonk frog was at risk of extinction or was it some endemic ants on the edge of the Mary river. Perhaps fish could have drowned...
To make matters worse; the Climate Change Council under Professor Tim Fridge'off Flannery, assured Queensland that anthropogenic global warming would ensure that the rivers in QLD would stop flowing and all the dams would run dry.
Voters too would not countenance continued water restrictions in the best rainfall in years, either. Especially after the Mary River solution's quash. Anna Bligh would lose her tenure as Premier if water restrictions remained.
Meaning there was no appetite to empty the Wivenhoe each early spring, as it is meant to be, as Brisbane (& the Gold Coast) does NOT have a guaranteed annual potable water reservoir reserve.
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All that above calculus is complicated by flood waters from the Lockyer valley that ultimately pass through the Brisbane River, and so Brisbane City too, but not through the Wivenhoe Dam. Enough water passed through the Lockyer alone to wash vast areas of suburbia in the Lockyer valley away.
What was the Lockyer river's impact?
SEQ will doubtless blame the Lockyer river system for a lot of their woes...
