The current flood emergency has seen Minister for Western Sydney, Stuart Ayres, make a renewed push for the Warragamba Dam wall to be increased.
Last year the Insurance Council of Australia withdrew support for raising the height of the Warragamba Dam wall by 14 metres, saying the money would be better spent buying back flood-prone Hawkesbury land. It followed fierce opposition by councils, including Blue Mountains, as well as Indigenous groups and environmental organisations.
But in an interview with ABC radio on Wednesday, Mr Ayres, the NSW government minister overseeing the proposal to raise the Warragamba Dam wall, said it would reduce the risk of flooding by 75 per cent.
"The most important thing is we are in an incredibly difficult weather environment," he said.
"The spilling we are seeing right now, raising the dam wall, would be very effective. Raising the dam wall is there to provide flood mitigation for downstream communities, when we are in situations exactly like what we are in right now.
"The capacity to hold floodwaters back behind the dam wall for a longer period of time... reduces the height of the flood downstream and increases the time frame [that] roads are open before they are cut because they are already low lying areas. This is really about creating better flood mitigation across the Hawkesbury/Nepean."
"It will reduce the risk of flooding by as much as 75 per cent ... it would remove the risk of flooding in most circumstances."
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Warragamba Dam started spilling on Wednesday March 2 at 3am. A draft Environmental Impact Statement for the raising of the dam has been developed by the NSW government and the public comment period has ended. The government will conduct a submissions report.
Dr Chas Keys, the former deputy director general of the NSW State Emergency Services, said the well over a billion dollar dam raising project would critically damage Indigenous cultural sites and pristine world heritage forest. He said the government's proposal was "misguided" and "greatly overstated the mitigation benefits" of raising the wall.
"There is a saying rivers own floodplains and they create floods every so often to remind slow learners," he told the Gazette.
He said several other rivers have a role in the flooding of the Hawkesbury region - big tributaries like the Nepean and the Grose enter the river downstream of the dam.
"There are plenty of other solutions ... evacuation routes .. lower the dam supply level and use the desalination plant. Building on floodplains is mad really .. eventually they will have to buy out people."
"Perhaps one of the best things they can do is restrict future development which is going on rapidly - there is an expectation of doubling the Hawkesbury population in the next 30 years - by 2050."
Bob Debus, a former Blue Mountains MP and NSW Environment Minister and now the Chair of the Colong Foundation for the Wilderness said Minister Ayres had been repeating "the same claims ... mindlessly for years now".
There is a saying rivers own floodplains and they create floods every so often to remind slow learners
- Dr Chas Keys
"The EIS for his dam wall proposal has been exhibited in recent months and it has been absolutely shredded by expert opinion. Much of the strongest criticism has come from various departments of the government of New South Wales."
"There is now a mountain of evidence to show that the proposal would do terrible damage to the environment, to Aboriginal cultural heritage and World Heritage values above the dam wall."
"The Insurance Council of Australia, representing the country's largest insurance companies, believes that a trade off for any downstream flood reduction can't be justified. However, when it comes to showing how, in practice, the dam wall raising would work to mitigate flooding below the dam, the EIS was quite hopeless. It was full of vague, inconsistent and inconclusive propositions that can prove nothing. The proposition about reducing flooding by 75 per cent just doesn't mean anything.
"Although what we do know for certain, as a practical matter, is that the raised wall would have no effect at all on the biggest, most dangerous floods."
"The Insurance Council in its public submission to the EIS says that its opposition is based on:
+unclear justification for the project's objectives
+inadequate appraisal of alternative interventions
+potential for further urbanisation of the floodplain
+lack of transparency in measuring benefit
+degradation of the World Heritage area upstream natural and cultural heritage."
"Against this sort of authoritative objection, Stuart Ayres' comments look to me not much better than self-serving propaganda."
Traditional owners have compared the dam raising to a potential Juukan Gorge catastrophe. Gundungurra woman Kazan Brown, from Warragamba, has previously told the Gazette.
"If the sites go under, the only place our culture will exist is in history books."