We’ve just had the first report from the inquiry into the floods at the beginning of the year in Brisbane and other parts of Queensland. The main recommendations are pretty close to what I put forward a few days after the Brisbane flood.
That just reflects the fact that it was immediately obvious, in hindsight, what changes needed to made. It would have been more impressive to get it right in advance. In this context, I feel some sympathy for the minister at the time, Stephen Robertson. As far as I can see, he was the only person to suggest lowering dam levels, but his requests for a response went nowhere with the bureaucracy. As a result, he got an adverse mention in the report. But if he had stuck to the rulebook, I doubt that anyone would have noticed.
John Quiggin 
Yeah, the conclusions seem pretty close to what you were saying. One improvement I think they made on your suggestions though, is that they don’t simply advocate a permanent lowering of the 100% mark. Instead, this lowering is triggered only temporarily and only in anticipation of a strong wet season.
This seems to give more water security in exchange for only a small increase in flood risk.
That makes good sense and i had come to the same conclusion myself
Wivenhoe was only built to mitigate floods, not to supply potable water. To revert entirely back to its original function would put the pressure back onto power generators and water authorities who have come to rely on Wivenhoe as a multifunction water storage unit. Using Wivenhoe for flood mitigation only would also put pressure onto the state coffers as a considerable investment is tied up in investment that essentially lies idle and is unproductive.
This new recommendation would have infrastructure authorities having to work with climate authorities. It still does not resolve the risk of rain records being further broken – that might require an increase in dam height.
Wivenhoe was built to store water AND to mitigate floods. To this end, water storage is set at a nominal 100% at half the dam’s capacity and flood mitigation capacity runs from 100% to 200%. In engineering terms, 100% is the safe long term storage for hydrological (if that is the right term) stability reasons. The dam can run higher for mitigation purposes but must be brought back down to 100% for long term integrity and operating safety margins.
People have short memories. A little while ago, we were down to 17% storage and we faced the dangers of severe water shortages for a couple of million people. The dam should be kept at 100% if possible. Deliberately running it down to 75% in expectation of a heavy wet season could be dangerous for water security. Prediction of wet seasons may become even more problematic with climate change affecting weather patterns and predictors for weather patterns. 75% is a very short sighted policy.
People who buy or build or rent in known flood areas knew or should have known the risk. I investigated more than several properties before I bought a house in the 1980s and as several of them were on or just below the 1972 flood level I simply did not buy them. In fact, I went for a considerable safety margin (more than double) over that flood level. I am not particularly clever. It’s easy to take such elementary precautions.
Changing water security policy to adjust for poor urban planning and poor personal decisions is not good policy. This is a clear moral hazard issue. Such policy will encourage further poor urban planning and poor personal decisions. I do however believe that pre-existing properties below the flood line should not be denied insurance help to the extent that they have been denied. There should be some social insurance for what is to some extent a legacy problem.
Correction: 1974 floods.
Why worry? The MSM has absolutely insisted (quite hysterically at times) that these floods were a result of La Nina, had nothing to do with so-called ‘global warming’ and, in any case, were nothing compared to 1890, 1840 or 1974.
True, the La Nina has something to do with the extreme rain earlier this year. The question is why was the La Nina so strong this year to cause excessive rainfall.
Could not possibly have something to do with global warming.
@Ikonoclast
It poses a risk for sure. So does a flood. It’s a case of drawing a line somewhere.
Floods and droughts were acts of God at one time, but ENSO is now a fairly well understood phenomenon, maybe not to the extent of predicting it 5 years out, but certainly to the extent of predicting whether the upcoming year is likely to be wet or dry. There’s no reason not to use those predictions to optimise the level of the dual purpose dam.
It was probably smart on your part to avoid buying flood-prone houses but that’s not a reason to make the best choices now. 🙂 Is chopping the floodable area out of modern Brisbane an option any more? Mitigation and designing to survive 30-year inundations look more realistic options to me.
Catching up-you dreadful old alarmist. I’m going to report you to the Galileo Society, and you’ll be getting a midnight visit from Alan Jones and his, ahem, ‘assistant’, David Flint.
Jim Birch, the position seems plain. There is disagreement over whether the water authorities made the correct decision, made by the accusers with the benefit of hindsight that the authorities did not have at the time. And, typically, to damage the Bligh regime and because they seem to enjoy destroying the reputations of anybody who gets in their way, News Corpse is confecting another ersatz ‘scandal’, aided and abetted by its televisual and radiophonic accomplices at John Howard’s ABC. They’ve even given some old dears (whose misfortunes I sympathise with and, I believe, News Corpse/ABC is cynically exploiting)the opportunity to appear on telly, become an instant and instantly forgotten ‘sleb’, and pour out the vitriol and bile on some poor blighter who was just doing his job in difficult circumstances. The endless production of rancour and hate is essential to Rightwing dominance of society, in that it constantly divides people against one another, keeps society perpetually stressed (the strategy of tension) and reflects the Right’s own inner spiritual dessication.
Wivenhoe was built as a result of the 1974 floods, water storage was an additional feature. When you think about it, flood mitigation and water storage are diametrically opposed functions – had Wivenhoe been empty it is unlikely that the latest flooding would have occurred.
How the Wivenhoe is operated has no effect on areas outside of the Brisbane River.
I am not particalrly impressed by the current enquiry. It seems to be a 20 or 30 years behind the times with respect the current enginnering pactices of designing for inherent safety.
As I understand the current thinking has done a 180 degree turn with respect flood mitigation dams. They only mitigate minor events and the lack of minor flood events allows the sediment and blockage to accumulate in the streams, down stream. When a major flood does occur, the damage is worst than if the dam hadn’t been there. For example, the last Brisbane flood peak water levels were much higher in the Centenary suburbs than the 1974 flood despite the peak river flow being less.
The current convention is that flood plain cites would be better off spending their money locating all their infrastructure above the expected flood level. (less important at 1 in 100 year, vital at 1 in 500 year or higher, etc).
That said, the flood mitigation system the British put in place a half a century ago on the Indus River seems to have worked really well in the recent flood on that river. Rather than trying to hold back the water, this system work by diverting it into storage basins so habituations were not flooded. This seems to have knocked the peak off the flood. A flood mitigation scheme on these principles is probably impractical for the Brisbane river valley.