Tuesday, January 18, 2011

Brisbane floods–could this flood have been mitigated?

There are genuine questions to be asked about why the Wivenhoe Dam failed to protect Brisbane from its worst flood since 1974.  The history here is that the Wivenhoe Dam was built in response to the 1974 flood and it was supposed to protect Brisbane from this kind of disastrous flood. What went wrong?

Andrew Bolt has been asking some serious questions about why the operators of the Wivenhoe Dam failed to release larger amounts of water in the days preceding the heavy rains that led to the floods.  The issue raised by Bolt is that the Wivenhoe Dam at the time of the deluge was too full,  that it was in fact at about 160% capacity prior to the rains, and that the dam was filling up fast to the point where the flood gates would have opened automatically.

Bolt takes up the case presented by senior engineer Michael O’Brien who claims that the Brisbane flood was avoidable. The issue seems to centre around the fact that the SEQ water failed to release sufficient water from the dam in the week prior to the heavy rains, leading to the release of 645,00 mega litres on the morning of the Brisbane flood. This release was due to the rather alarming increase in the dam storage levels to about 190% capacity.

You can read the whole thing here.

Like Andrew Bolt I am not familiar with the information that has been provided. On the other hand, I have experienced a flood that was due to the opening of the Warragamba Dam’s floodgates. The effect of that action was quite significant, leading to serious flooding in the Richmond-Windsor district.  There is some similarity in circumstances because the flood was preceded by a week of heavy rain and then came the rising of the rivers which cut off the townships of Richmond and Windsor. In the case of Brisbane, as pointed out by Germaine Greer, the Wivenhoe had been as low as 10% capacity at one point, meaning that the SEQ operators of the dam might have been reluctant to release greater quantities of water.

At least Anna Bligh has ordered a Royal Commission into the floods, and hopefully the Royal Commission will examine all of the data that will explain why the Brisbane floods happened in the first place.

This is a different issue from the floods in Ipswich, Toowoomba and the Lockyer Valley.  The wall of water that came beating down on the residents of that region was also probably avoidable. 



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