There’s already some finger-pointing about the management of Brisbane’s dams in the weeks leading up to the flood. I don’t want to deal with that while the emergency continues, but I will make a couple of suggestions regarding future policy in Brisbane and elsewhere

* The historical statistics on the frequency of severe rainfall events (both droughts and floods) have proved to be of little value. Everywhere in Australia, we need to work on the assumption that extreme events will be more common in the future than they were in the (pre-2000) past.[1]

* As regards Wivenhoe Dam, we need a much more cautious approach to flood mitigation, going into wet seasons with a substantially larger reserve capacity. This in turn will reduce Wivenhoe’s usefulness as a water supply source, and buffer against drought.

* One response that is immediately available to us is to turn on the water recycling plant, built at great expense during the drought and never used. Current policy is to turn it on when average dam levels are at 40 per cent. This trigger should be raised significantly. As a very rough guide, it appears that when our dams are at 100 per cent of normal we currently have enough storage for four years supply. If instead we cut the maximum to three years supply (75 per cent0, we could (roughly) cancel the impact on supply by turning on the recycling plant at 65 per cent (40+25)

On a personal note, I’ve had some reports from home and it appears that cleanup will go faster than expected and that our biggest loss (the car) is covered by insurance.

Many others are not so lucky. And, as was discussed in comments to the previous thread, floods in poor countries regularly cause many deaths (400 in Brazil and 40 in the Phillipines in the time I’ve been following our own flood) and wipe out the few possessions of very poor people. If you are giving to flood relief appeals for Queensland (as I hope you are), please think about also sparing a few dollars for emergency relief or long-term development aid for the truly poor.

Update It’s been argued pretty convincingly in comments here and elsewhere that the additional mitigation capacity in the estimates above would only have had a marginal influence on the current floods, given the volume of rain that fell. Still, I think the basic premise is right. We will need more mitigation capacity and that means less water at higher cost.

Another point I meant to make earlire is that more reliable forecasts of El Nino and La Nina events would be of great value in managing water supply in a highly variable environment.

fn1. I will have a lot more to say about human-caused climate change in the near future. But until I’ve had my say, I request everyone to avoid any discussion of the AGW topic in this thread – failure to heed this warning will lead to deletion and may result in a permanent ban. Feel free to continue discussion in the agnotology thread.