Australian state leader Premier Dominic Perrottet is asking the federal Labor government to help fund the raising of the Warragamba Dam wall in a bid to reduce flood risk to the community downstream of Sydney’s biggest dam.
The suggestion was first put forward in 2016 and has received renewed attention this week after several areas across Australia’s most populous state of New South Wales were declared “natural disaster zones” following days of storms and flooding across the state.
The flood has affected about 40,000 people across Sydney, the Hunter and Illawarra, with 50 evacuation orders in place. Over 2,000 homes have been assessed for damage so far, with 239 found to be not habitable and a further 973 needing repairs.
A Department of Infrastructure report following community review called for raising the Warragamba Dam by 14 metres, which subsequent reports have said would have reduced the flood peak in the March 2021 event by 3.5 metres, reducing the flood to a minor flood level.
The floodplain, on which around 140,000 people currently live or work, has already been flooded three times in the last 18 months, causing several hundred million dollars in damages.
The report noted that the project aims to create “airspace” above the current full supply level of the dam, which could hold back approximately 1,000 billion litres or 1,000 gigalitres—the equivalent of two Sydney Harbours.
“This would delay and reduce the flood peak and flood extent for downstream communities and allow more time for evacuation—reducing the risk to lives, flood damages, and social disruption caused by major floods in the valley,” the NSW government explained in its submission.
According to the government’s plans, the extra retention volume of the dam would only be used for flood mitigation purposes in order to maintain the structural integrity of the dam and minimise the duration and extent of upstream inundation. In the case of a flood, the water in the raised dam would take 14 days to completely discharge.
Support for the Raise
Perrottet said that raising the Warragamba Dam is crucial in protecting homes downstream, although the project will be “very expensive” and complex due to the environmental and planning issues involved.
The NSW Premier revealed that he is pushing the federal government to commit to a 50-50 funding split, as the project cannot proceed without approval from the federal level.
The Options Assessment Report indicated the 14-metre raising would cost between A$500 million (US$342 million) and $1 billion, but the NSW Labor opposition argued it had exceeded over $1.6 billion.
Meanwhile, Mayor of Hawkesbury City Council Patrick Conolly on, July 7 urged the government to get the project off the ground instead of “trying to keep protest groups happy.”
“Enough is enough, they’re saying all the right things and saying they’re going to do it, but they keep coming up with new ways to delay the project,” Conolly told 9News.
“But I’m here to say, us downstream, we have real lives, and we’re real people, and we are just as important if not more important than the trees behind the dam wall.”
The sentiment was echoed by Minister for Western Sydney Stuart Ayres, who’s also the deputy Liberal party leader for the state. Ayres said, “you cannot stop the flood from happening; you can only choose where you slow the water.”
“We already don’t allow development on high-risk flood zones,” Ayres told The Daily Telegraph. “Raising the dam wall will not allow one extra home to be built there.”
Concerns about raising the wall have also been raised, with NSW Opposition leader Chris Minns arguing that the project will bring the state debt to $183 billion, which will “have to be paid off by future generations of taxpayers.”
“The cost of the project is blown out from about $650 million to over $1.6 billion, and the New South Wales Government still hasn’t explained why no money has gone towards this project,” he told 7News on July 8.
“We’re sceptical about it. We’re sceptical about its implementation, the money being provided for it.”
Minns suggested that the government should instead focus on building more evacuation routes and lifting infrastructures for flood-prone areas like Hawkesbury and the Penrith region.
“Our real concern is that the government on the eve or just after a flood insists that this is the solution to the problem,” Minns said. “They’ve also got a plan to double the population on the floodplain, which we think could make a terrible situation far, far worse.”
Wollondilly Mayor Matt Gould also opposed the plan, saying that raising the dam wall “isn’t the silver bullet” given that more than 50 percent of floodwaters can come from the Upper Nepean and catchments that are effectively downstream from the proposed wall.
“None of this water is captured by Warragamba Dam, and all of it flows through to the Lower Nepean and Hawkesbury, so we would have been facing significant flooding along the Hawkesbury-Nepean even without the impacts of water from the Warragamba River,” Gould said on July 8.
The proposals had been delayed before the recent flooding in the face of calls for more thorough environmental impact assessments for the flooding that could last in some areas of the proposed catchment area for up to 14 days.
Community submissions from environmental advocacy groups point to habitat for Macquarie perch and critically endangered regent honeyeaters, as well as critically endangered woodland and forest communities that would be temporarily inundated. A part of the proposed catchment is also part of the Blue Mountains World Heritage Area, which the United Nations recognised in 2000. Other parts of the catchment in the Burragorang Valley were used for decades as farmland and other uses and were subsequently protected as National Parks.
According to Ayres, any temporary inundation from flooding would affect 0.04 percent of the World Heritage site. Unfortunately, during the 2019 bushfires, significant parts of the World Heritage Area were impacted, leaving the area even more sensitive to further disturbances.
Other impacts also include the inundation of cultural sites of the Gundungurra nation.
But NSW Farmers President James Jackson noted while there’s an environmental impact to having a dam, “there’s also an environmental impact to not having a dam.”
“If you think of the damage caused by these floods, you’d probably pay for these raised walls already,” Jackson told the Daily Telegraph on July 7.