Why Did Brisbane Flood?

Last week I promised to cover three topics regarding the Brisbane floods. I have already spoken about how the floods started, I’ve done a couple of posts about the impact of the floods and today I’m looking at why Brisbane flooded.

My road during the peak

My road during the peak - House on right are submerged

A simple guide to why Brisbane flooded.

This guide is simple; it has to be because it’s written by me, BobinOz. Is it factual? It might be, but I have had to research a lot of information which I myself cannot be sure is correct.

Is it the definitive guide as to why Brisbane flooded? No, but it is my definitive guide. The way I see it, there are four schools of thought on why Brisbane flooded.

The ‘Wivenhoe Dam Stuffed It Up’ Theory

After the last floods in Brisbane back in 1974, Wivenhoe Dam was constructed so that this would never again happen in this city. So naturally, many people are arguing that the dam let us down or, at the very least, the operators got it wrong.

Here’s what I know about Wivenhoe Dam. It has a storage capacity of 225%. 100% is supposed to be for drinking water storage and another hundred percent reserved for flood mitigation. The final 25% is really just the equivalent of a red alert area on dial. When the dam gets into this area, we really are in trouble. Because if it gets to 225% it can literally disintegrate which would, of course, be catastrophic.

When I first arrived in Australia, November 2007, the dam was down to around 18% and this city was in a bit of a panic regarding its drinking water supply. It took almost a year before there was enough water in it for Brisbane to relax.

Yet incredibly, in the few days before the floods, the dam received around 100% of its capacity each day.

The controversy over Wivenhoe Dam is that instructions in place since the beginning of 2010, which the dam operators were required to follow, state that there should be 100% of water left “after” a severe weather event. Before that the level used to be somewhere between 60% and 70%.

That is to say that these days Wivenhoe Dam is being used for 100% water storage with the 100% plus the red alert area for flood mitigation, whereas before that it was used for 60% water storage with 140% or more available to prevent flooding.

So the big debate is, would that extra 40% had it been reserved for the emergency have saved the city of Brisbane? Or, to put it bluntly, did the owners and those charged with operating the dam stuff it up?

The ‘We’ve Simply Had a Lot of Rain’ Theory

We were all shocked by the wall of water or “inland tsunami” that rushed through Toowoomba and the Lockyer Valley two days before Brisbane was flooded. We saw shocking and frightening images with a death toll to match.

I think the records show that Brisbane had slightly less rainfall this time than it did in 1974. But inland, around Toowoomba, the rainfall was unprecedented as those television images showed. The result was that the Lockyer Creek and Bremer River were also pouring massive amounts of water into the Brisbane River below the dam.

Some argue that no matter what Wivenhoe Dam operators had done, whether they’d saved that extra 40% for flood mitigation or not, Brisbane would have still been flooded. But I’d say logic dictates that the flooding would not have been as bad if they had saved a little more room in the tank.

The ‘Whadya Expect’ Theory

The third but least talked about theory is the whadya expect theory. It’s very simple, what do you expect when you build on a floodplain? What do you expect when you build a large city in an area that in many parts used to be a rainforest?

What do you expect when you build a community in an area known for its harsh and extreme weather conditions; a place that has received severe flooding at regular predictable intervals every 40 or 50 years throughout history; somewhere that has a natural subtropical climate?

I think this theory has a point. Made me think. Of all the cities and all the towns in all the world, I chose to walk into this one!

There is a fourth theory, which I am happy to cover.

The “It’s Climate Change, It’s Global Warming” Theory

What piffle! Of course it isn’t global warming!

In this latest flood the river peaked at around 4.46m. In 1974 it peaked at 5.5m. In the Brisbane floods of 1893 the river peaked at 8.35m and in 1841, 8.43m. There was no talk then of global warming back then, no industrial revolution and certainly no cars.

For any of you in the “global warming industry”, when are you going to get a proper job? Although I do think whoever it was who sort of changed the name from “global warming” to “climate change” was a really smart cookie. Climate change covers everything, doesn’t it? In Melbourne, they have climate change every day! Have done for centuries!

Here’s what I think

I blame the clever people. Mainly because that gets me off the hook. But more importantly, because between them they have had nearly 40 years to solve this problem, a problem that has regularly visited this area in a very predictable cyclical pattern.

Not only have they failed to solve the problem, despite all the money spent, they allowed even more properties to be built in flood prone areas because they thought they had solved it. So instead of something like 6,000 houses suffering severe flooding in ’74, this time almost 12,000 were completely submerged.

So there you have it, the BobinOz guide to the floods in Brisbane. I suspect I could have made this post is a little shorter, for example, like this:

Why did Brisbane flood?

“I dunno!”

Finally, I’d like to leave you with this short YouTube video. As you know, I was pretty much isolated within a couple of hours after the floods began here. So my video, which you can see here, could only show you what flooding was like in Western suburbs.

This video has no such restrictions and gives you a very good idea of what went on that day around the rest of this city. It also goes well with my post today because it covers some of the same topics I have discussed above.

Maybe it’s a teeny big dramatic, but the guy who made it does work in the media, it’s his job. But it is well worth watching……

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{ 16 comments… add one }
  • Warwick Wakefield January 27, 2013, 10:05 am |

    Hi Bob,
    first of all, about global warming.
    We have all seen programs, especially on the ABC, where the matter is presented as a contest between science and anti-science, between the scientists who make their living in a climate science department and journalists who don’t know what they’re talking about. This manoeuvre is done so dishonestly, in such bad faith, that it is astonishing that they have the nerve to do it.

    The fact is that amongst scientists there is huge disagreement. Included amongst the names of those who reject the global warming theory are figures from the world’s top universities and research institutes, Harvard, Yale, Princeton, Massachussets Institute of Technology, University of California at Los Angeles, Berkeley, San Diego and many more. The dissenters include Nobel prize winners and other first world class scientists. To present the scientists who disagree with the global warming scare as somehow equivalent to faith healers is a disgusting ploy. It succeeds here in Australia because the ABC and Fairfax media are totally committed to the idea that human emissions of carbon dioxide are going to make the Earth uninhabitable. (If you like, I can send you a publication, by email, that lists some few hundred of the world class scientists who reject this silly idea.)

    Why do so many “climate scientists” support this theory?
    The answer was provided by Professor Stuart Franks from the University of Newcastle (in NSW). He pointed out that the overwhelming majority of the people who go into “climate science” to make a career were environmental true believers before taking up “climate science,” often before starting their university science studies.
    It is worth digressing a moment to examine the outlook of the environmental true believers. The fundamental, and fundamentalist, belief is that everything “natural,” everything that you’re likely to see on a David Attenborough TV program, is good. Humanity is bad. Humanity is a plague destroying the Earth. Maybe humanity that lives close to nature, with windmills and home built housing is more or less acceptable, but humanity with aeroplanes and cars and nuclear fueled power plants is terribly wicked.
    The theory of human induced, catastrophic global warming is defended at all costs, and damn the evidence, because the theory fits with the fundamental belief.

    The global warming scare mongers keep repeating that we can see the world’s getting hotter, look at the heat waves this summer. They do not mention that Watkin Tench, who came here with the First Fleet, reported heat so bad that multitudes of fruit bats and parrots (lorikeets) fell dead from the skies and littered the ground. There were no fires that made this happen, just heat.
    We both know that there is a difference between weather and climate, and this heat in 1889 was weather, not climate. But the global warming scaremongers often point to weather events and say, “This is global warming.” They are keen to point out the difference when we experience record cold and rain, but when we get a bit of heat they again start beating the global warming drum. If they held to the principles of science when they discussed the matter you could cut them some slack but their behaviour is so shameless, so disgusting, so infused with the kind of lies and distortions and propaganda that the Soviet Union perfected, that they must be simply condemned and opposed at every opportunity.

    If the global warming establishment were sincere they would have publicly disowned Tim Flannery, who assured us that hot dry weather is here to stay, and that, even if we did get some good rain by a freak of nature, it wouldn’t do any good because the ground would be so dry that all the rain would be soaked up by the dry ground and the dams would never fill again.
    Has Flannery lost his job as the highly paid head, or public spokesman of, the Climate Change Commission?
    Have climate scientists come out to declare that he was making predictions which were based on the fundamentalist belief in human evil, and had nothing to do with the available evidence?
    Not a bit of it.
    He is still a hero, just as the charlatan Paul Ehrlich is still a hero, to the environmentalist true believers.

    Even if we don’t have science doctorates, we ordinary folk can recognize the lies, exaggerations, propaganda and money interests of the scientists who team up with Greenpeace and the like to promote this baseless scare campaign.
    When they apologize and confess and show a bit of humility, cut them a bit of slack.
    Until then, give no quarter.

    • BobinOz January 27, 2013, 9:03 pm |

      I couldn’t agree with you more Warwick, I’m with you 100% on everything you say. It astonishes me that Tim Flannery has got away with the things he has and still remains very lucratively employed.

      There is no justice.

      I’m sure my comments in the above post make my position clear, but if you’re interested, I also have more to say about it in my post about Australia’s carbon tax.

      Thanks for taking the time to give us your views, it’s appreciated.



  • Bob January 9, 2012, 2:02 am |


    The Wivenhoe Dam will not crumble if it exceeds its maximum flood mitigation level. As an emergency feature it has a ‘fuse plug’ which is designed to stop this from happening, it is this fuse plug which progressively gets ‘washed’ away down to a safe level but in so doing it causes an uncontrolled water release. The fuse plug was installed in 2004 after extensive modeling of possible flood events. As far as I can determine the 2011 flood set the record for dam inflows but was nowhere near the exceeding the capacity of the normal dam gates.

    Also those who designed and built the Wivenhoe Dam were well aware of its limitations, only politicians and journalists ever put it forward as absolute protection against floods. The 40% capacity debate is silly, 2 days extra rain would have shown the futility of any attempts to control nature.

    Unfortunately, it wouldn’t matter if you had 40 years of 400 years, you cannot fix the problem as there is nowhere to further store large quantities of flood waters and even if you could there is always the possibility of a weather event that will overwhelm the defenses – it is only a matter of when. As you have already pointed out, Brisbane is built on a flood plain and short of moving the city it will always be vulnerable to flood.

    I lived in Brisbane during the 1974 flood (we got flooded) and people in the know thought that one was a bit of a dud! Our house was built on the flood plains of East Brisbane less than 20 years after the 1893 flood (like so many others). The 1893 flood level would have greater than 2metres above the floor of this high-set Queenslander yet they build it against all experience and reason, my Grandparents bought it despite knowing about the possibility of flood, and I still own it to this day despite 1974 – somethings just don’t change, wishful thinking being one of them.


    • BobinOz January 9, 2012, 2:41 pm |

      Hi Bob

      I can’t remember where I read or heard about it now, but I am sure someone somewhere said that if the dam overflows the structure would become severely compromised. That said, the ‘fuse plug’ system you talk about and the consequent uncontrolled water release doesn’t sound like much fun either.

      I certainly don’t claim to be an expert in these matters and I’m not sure whether you are claiming to be one either. But I do still say that as a layman looking on, I can’t help but think that better management of the dam levels would have resulted in better flood control, possibly complete flood control.

      Many people disagree with that, like yourself. That’s what makes this a debate and probably none of us will ever know the real answer. As you say, maybe there is no real answer to flood management in Brisbane, and maybe it is just a matter of time before we get another flood.

      Thanks for giving us your views, it’s appreciated.



  • Kirri January 7, 2012, 11:57 pm |

    You seem to have some of your terms a little mixed up. Melbourne does not see climate change every day. They see a change in the weather every day. Climate and weather are not the same thing. Yes weather is unpredictable and very, very variable, but climate is about averages and thus significant changes in climate are very different to changes in weather.
    You also say they changed the name from global warming to climate change. They didn’t, people have been talking about climate change for over 50 years and the frequency of the use of this term and global warming have risen equally over the past 40 years. Although many people use the terms interchangeably they actually refer to two different phenomena. It doesn’t mean that climatologists no longer believe the earth is warming, they do and it is, but when they talk of climate change they are refering to much more than just warming.
    Having said that, I’ll agree that it wouldn’t be correct saying that the Brisbane floods are the result of climate change.
    And those in the climate change industry are working to get us cleaner air and a healthier environment. Based on how much you seem to appreciate the Australian environment I would have thought you’d have been for this even if you don’t agree with climate change.

    • BobinOz January 9, 2012, 2:24 pm |

      Hi Kirri

      Thank you for the clarification on some of those terms, most helpful and educational. I stand corrected. I am also pleased to see that we do agree that the Brisbane floods are not a result of climate change.

      And yes, I do love the Australian environment and anything that makes our air cleaner should be a good thing. I’m just not keen on the way it’s being done, you know, Al Gore flying around in a private jet, living in a huge mansion and telling US how we can cut back on our carbon emissions. Most hypocritical.

      • Kirri January 9, 2012, 5:31 pm |

        Well when I get a job in the environmental industry, as I’m currently trying to do, I promise to try my best to avoid doing things like this and just try help protect the environment. But then again, I doubt I’m ever going to be able to donate millions of dollars to environmental charities like Gore has. He’s a hypocrite yeah, but he is doing some good. Maybe he thinks it’s like buying those carbon offset credits when you fly on a plane. Giving $20 to plant a couple of trees totally makes up for the emmissions from your flight yeah? So surely giving millions of dollars makes up for a complete lack of sustainable living. Right?

        • BobinOz January 9, 2012, 10:46 pm |

          “…he is doing some good.”

          No he isn’t! He is trying to tell people it’s our fault all this is happening and that we have all got to change our ways, whilst he tidies up at the box office and lives the life he’s telling us not to live.

          Meanwhile, the real cause of climate change is the Sun!

          • Kirri January 10, 2012, 5:31 am |

            Except the sun is cooling so how exactly is that causing temperatures on earth to rise? Studies of incoming solar radiation show no significant trend but if anything it is slightly downward. And yet earth temps are still going up. There has always been a strong correlation between solar radiation levels and temperatures on earth until recently when the two have split and begun to go in opposite directions.

            • BobinOz January 12, 2012, 2:15 pm |

              I thought there was some kind of delay built in, something to do with the sun heating up the oceans and then sometime later the oceans giving of carbon emissions, meanwhile the sun may well have started cooling down again.

              I vaguely recall some kind of 800 year gap?

              Anyway, I know this is your chosen subject now, so I’m sure you can hit me with loads of facts and figures, but the bottom line for me is I do not believe that us humans are the cause of climate change, global warming or what ever anyone wants to call it. I think it is happening purely because this is planet Earth and that’s what happens here. It goes in cycles.

              The problem is if everyone believed that, there would be no climate change industry. And scientists need something to do.

              • Kirri January 13, 2012, 7:39 pm |

                The only reference to an 800 year gap that I could find is that historically, changes to CO2 levels lag behind temperature changes by about 800 years. Could this be what you are recalling? Its a pretty popular argument against anthropogenic climate change because people assert that temperature changes historically lead to changes in CO2 levels, not the other way around. The problem is they are ignoring the fact that with this warming trend, the rise in CO2 occurred first and the temperature has followed.

                Climate does occur in cycles but scientists havent been able to find causes for the current warming in the natural cycles.

                Just a couple of important facts and figures that I can throw at you. Humans are emitting an extra 26 billion tonnes of CO2 each year. That has increased atmospheric CO2 concentrations, which for the past 8000 years have been fairly stable around 275-285ppm, to over 390ppm. That means we have increased CO2 concentrations by over 35% in the last 150 years. I don’t understand how you can look at figures like that and assume that humans aren’t having an effect. I know that the whole climate change debate has gotten overly political and commercialised, but that doesnt mean the science is wrong. In my time at uni I would have had probably about 100 lecturers including guest lecturers and all, and only ONE of those didnt seem to accept anthropogenic influences on climate change. He was an economist. Do you really believe that all the rest of us just have an agenda to promote. We accept this because it is what the science is telling us. I accept that we can’t keep polluting the world and ignoring the consequences.
                And I’m sorry for all the preachy messages, but this is what I’m passionate about and I can’t help but get worked up when I see people arguing against science with claims that can’t be backed up. Yours at least has some scientific evidence so it’s not really your fault, but so many of the anti climate change debates are purely myth and misunderstanding. Plus I was a little offended by your “you in the “global warming industry”, when are you going to get a proper job?” quote and that kinda set me off.

                • BobinOz January 13, 2012, 11:18 pm |

                  Ah, yes, the “get a proper job” thing, I thought that would wind some people up 🙂

                  Anyway, I knew it would end up like this. 26 billion tonnes, 275-285ppm, rising to over 390ppm, 8000 years, 35% in the last hundred and 50 years, blah blah blah. It doesn’t matter what you say, I just don’t buy it.

                  Yes, it was the changes to CO2 levels 800 year lag thing that I was remembering. But none of this really matters, I don’t agree with you and you don’t agree with me. We differ.

                  My comment about getting a proper job may have irked you, but what irks me is people claiming that scientists have proved that humans are responsible for global warming. You yourself implied it, but just the other way round when you said “arguing against science with claims that can’t be backed up”

                  It is not up to us to prove you scientists wrong. When I did science at school, if I remember correctly, for anything to be scientifically proven it had to be done so under controlled conditions and be repeatable.

                  You just can’t do that with “global warming”. Sorry, but for me science has not proved anything with regards to climate change or global warming or whatever you want to call it.

                  All that aside, I really like you Kirri.

                  • Kirri January 14, 2012, 9:39 am |

                    🙂 Thank you. I’m trying to avoid coming off as some of your other commenters have. Ones like Matt from the snake discussions, and the guy with the Martin Bryant conspiracy theory. They were also just arguing something that they were passionate about and because it differs from what we believe it comes off as a little crazy (Maybe also because it is a little crazy hehe). So because I’m arguing against what you believe here I’m hoping it doesn’t come out in the same way.

                    Now you talk about proof but a lot of science can’t be proven. Just some things that you probably believe that haven’t been proven are evolution, plate tectonics and gravity. I know there are a whole lot of people who don’t believe in evolution and a friend of a friend doesn’t believe in plate tectonics but tell me you don’t believe in gravity and I might have to stop reading your blog because I will hence label everything you say as that of a crazy person hehe. But you can’t prove gravity, you can only disprove it and since that hasn’t happened and every line of evidence we have supports it then it is accepted as true. So science usually talks of evidence rather than proof.

                    In terms of climate change we have a whole range of evidence that the world is warming. We have evidence of an enhanced greenhouse effect which could be causing the warming and we have evidence that this enhanced greenhouse effect is due to amounts of CO2 that have been released by human actions. What we don’t have is any evidence that this warming is coming from another source, such as the sun, and hence leads us to the conclusion that the current warming trend is caused by humans actions. So my claims are backed up by science. It’s just a matter of sorting out the science from claims of science. If you actually look at most of the skeptics arguments from a science point of view most of it just becomes laughable. Things like leaving off the last 20 years from graphs and people claiming to be head of climatology departments that don’t actually exist. Seriously Tim Ball is very vocal about denying climate change and has appeared in films like the Great Global Warming Swindle. He claims that as former head of the climatology department of the University of Winnipeg he should know what he’s talking about right? Well except that the University of Winnipeg has never had a climatology department. This is completely irrelevant to our debate by the way I just think its funny. But if they have to lie about their credentials then you should probably take everything else they say with a grain of salt.

                    • BobinOz January 17, 2012, 3:38 pm |

                      I think we will just have to agree to disagree on this one Kirri. Yes, I know there are a lot of claims and counterclaims in this argument and there are distinctly two sides to the story.

                      Not being a scientist or a climatologist myself, I have to rely on the information/propaganda that I read and hear about in the media. So I end up having to go with my gut feeling and that feeling is firmly on the side that says it isn’t us humans that are causing this planets climate change.

                      When governments like ours here in Australia start introducing a carbon tax, and when industries are being born and new job titles created, I get even more suspicious. There’s money in them thar global warming.

                      Global warming is not a religion, you do not need to try and convert me. If it’s all the same with you, I’ll stay as a nonbeliever.

  • BobinOz February 7, 2011, 1:11 pm |

    Thanks Ian

    We’ve been having this sort of weather for centuries, it’s only during this one that people have thought to give it a name, make films about it, write books and apply for government funding to study it.

    And frankly, some of the things they have “found” when studying it haven’t done the rest of us any favours.

  • Ian February 4, 2011, 10:21 pm |

    “What piffle! Of course it isn’t global warming”

    “For any of you in the “global warming industry”, when are you going to get a proper job?”

    Nicely put Bob!

    In my view Bob Brown from the Greens is as culpable as the dam operators in this disaster. They and the Government fell for the rubbish from the global warmists and they operated the dam as if the dry weather would continue for ever.

    Simply, they kept way too much water in the dam over the preceeding weekend.

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