1. The Australian media doesn't run on a 24-hour "outrage" cycle. We don't have any way to blame this on some targeted political figure (though certainly political figures have come in for some criticism). People will get blamed (particularly those who were in charge of the dam that was supposed to prevent this from happening again) but it'll happen slowly and in a controlled manner, not in a rapid flurry of 24-hour-news-station activity. We have a procedure for finger-pointing, and it's called a Royal Commission... we'll spend a year investigating and holding hearings and then eventually find the correct people at whom to tut-tut.
2. The death toll is relatively low. Very low in Brisbane itself (where the rise of the floodwaters was gentle) and a mere dozen or so in other parts of the state (where flash floods did occur). Sad and all that, but still on a relatively small scale.
3. No breakdown of order. Partly because a river flood is nothing like a hurricane (the city itself wasn't cut off, and if you're in an affected area you can walk five blocks to an unaffected area) and partly because of the different quality of people in the two cities.
4. New Orleans already had serious problems (poverty, race relations) which were only exacerbated. Brisbane was a pretty nice place, and it's still a pretty nice place (except for the parts which are now ruined).
In answer to your question, though, this isn't a once-in-1000-year flood... more a twice-a-century sort of flood... we had floods in the 1890s and again in 1974. The Wivenhoe Dam was constructed to prevent the 1974 flood from ever happening again. It didn't work, partly because the folks in charge of operating the dam didn't start releasing water until it was too late... which was itself partly because they've been worrying for most of the last decade about running out of water and forgot that too much water is also a problem.
There's a reason why the architectural style known as a "Queenslander" is a house on stilts though -- Queensland is not a stranger to floods.