This morning, the opponents of flood safety in the Hawkesbury were falling upon a ‘leaked’ State Government report that stated something so obvious it’s banal – that in the event of a major flood, the water has to go somewhere.
Their tortured argument says if Warragamba Dam is raised, providing a buffer against future floodwaters, then that water will need to be released progressively after the peak. This means river levels will remain elevated for a number of weeks as that release occurs – affecting water filtration and sewerage treatment plants downstream.
Scarcely surprising. Any major flood is a catastrophe with effects lasting weeks or months. There is no scenario where a major flood would not disrupt in this way.
Those confecting outrage even suggest that raising the dam would *worsen* the effects of flooding in the Hawkesbury – a staggeringly misleading and contemptible statement.
Such a statement is as brazen as telling people that vaccination will give them COVID. It is geared to provoke outrage. It counts on people not knowing the facts.
What they don’t concede is that in the event of a major flood, if the dam has not been raised, those same floodwaters would hit the floodplain all at once, catastrophically. It would cause flooding to a far higher height than would otherwise be the case.
The ‘Resilient Valley, Resilient Communities‘ document laid all this out in 2017:
In the event of a 1:100 year flood, 1000 houses would be inundated with a raised dam, instead of 5000 without. In an 1867-level flood, that’s 5000 houses instead of 12,000. The severity or frequency of flooding will be reduced overall by 75%, the damage bill reduced tenfold. The flood height would be lowered by many meters.
Flood damage reduction from raising Warragamba Dam, from the ‘Resilient Valley, Resilient Communities’ report (2017)
Imagine if the floods we endured in March this year were 3-5m lower – on the order of the February 2020 floods. Many houses would have been saved. Now imagine if that flood was another 3-5m higher. Those are the margins we are talking about in choosing not to implement flood mitigation.
Stating that the backlog of floodwaters would be released progressively from the dam in a responsible way is so obvious as to be no admission at all. Not focusing on what *would* have happened if that buffer had not been there is irresponsible.
Opposing flood mitigation condemns thousands of houses on the floodplain to inundation when the next big flood comes, and you should remember that when you vote.

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