The Australian “The Climate Sceptics Blog” takes a look at the Wivenhoe dam’s involvement in the catastrophic Queensland flood. I disagreed with the opinion that it might be sufficient to show that operators SEQwater did not undertake a proper, impartial risk assessment.

The question of having to prove the “AGW is not true” in the Wivenhoe case may be a little extreme.

Rather, they would need to show that the operators had a revised policy that gave due weighting to the Australian Government’s Report. I have only read the results. It says here quite clearly

“Observed trends in exceptionally low rainfall years are highly dependent on the period of analysis due to large variability between decades.”

In other words the results are not robust. This is not surprising. The report only looked at period of 40 years, so could say little about the frequency of once-in-a-generation extreme events. It does not say that floods will never occur again, like they have in the area since time immemorial.

If the authorities did not undertake a proper risk assessment of future scenarios based upon a balance of existing knowledge, and the report, then the change of purpose from flood management to reserve storage facility is flawed. This is unless there is near certainty that a climatic shift has occurred in a definite way. This was because

1. The Report clearly stated that its results were not robust, AND did not predict that extreme rainfall would never happen again.
2. There is a further complication that may hold. If there is not an extreme climatic shift (or only a partial one, or are in a slow transition from one state to another), then an area with extreme floods in the past will still likely have extreme floods in the future.
3. Further, the lack of extreme floods for an extended period might pose a greater risk of extreme flooding in the immediate future.

This whole thing becomes a complex matter of balance of risks. That is why they should have solicited expert opinion on risk management from different perspectives, and tried to eliminate any corporate or individual biases. Furthermore, a risk management body should have publicly stated this change of use of the Wivenhoe Dam, so that householders could make adjustments to their risk portfolios.

These conclusions are based analysis of unfolding news reports hype on droughts and floods; the hype that exists for Catastrophic Anthropogenic Global Warming; and my developing analysis of Climate Change (see here, here and here) This comment is not intended as a legal opinion on the case, nor should it be taken as such.