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.
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?
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……