Government says scheme for Warragamba dam lessens flood risk for residents, but activists say it jeopardises wildlife and Aboriginal sites

This article is more than 2 years old

This article is more than 2 years old

Conservationists have written to the Unesco requesting a moratorium on New South Wales government plans to raise the height of Warragamba dam, which could flood parts of the Blue Mountains world heritage area.

The group of 14 signatories, led by the former NSW environment minister Bob Debus and including Bob Brown, Christine Milne, the Australia Conservation Foundation chair Paul Sinclair, and Gundungurra traditional owner Kazan Brown, wrote to the chair of Unesco’s world heritage committee last month warning that natural heritage values of the area would be “significantly degraded” if the proposal were to go ahead.

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The NSW government announced the plan as part of a broader flood mitigation strategy in 2016 and plans to begin the construction by mid-2020.

It would involve raising the wall of the dam, which was constructed in the 1960s, by 14m. That would open up 1,000ha of the world heritage area and 3,700ha of the surrounding national park to flooding.

It would also potentially flood more than 50 Aboriginal heritage sites belonging to the Gundungurra people, including cave paintings, and destroy 38% of the remaining Eucalyptus benthamii population, which would see it upgraded from vulnerable to critically endangered on the threatened species register.

Gundungurra traditional owners have already raised concerns about a lack of consultation around the proposal.

According to the letter, inundation caused by raising the dam wall would also impact the Eucalyptus mollucana woodlands in the Burragorang Valley, which are home to 400 different animal species including the critically endangered regent honeyeater and the last wild population of emu in greater Sydney.

“I think it’s a damn fool idea,” Debus told Guardian Australia.

Debus was environment minister under a Labor government when the Greater Blue Mountains world heritage area was declared in 2002, and passed legislation following that declaration to protect the area against further inundation. That legislation, which was supported by the Liberal party, remains in place and would have to repealed for construction to go ahead.

The project would also require the approval of the federal environment minister, Josh Frydenberg, under the Environment, Protection, Biodiversity and Conservation Act, which covers world heritage areas.

Debus accused the NSW government of trying to open up land in the Hawkesbury Valley for housing development and said it had taken a deliberately un-scientific approach. He drew a parallel to new laws protecting feral horses in Kosciuszko national park.

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“You have this situation which is raised again in the situation with the brumbies, where the governmetn is almost defiantly ignoring good sense and science,” he said. “Almost defiantly ignorant. It’s astonishing.”

Western Sydney minister Stuart Ayres said raising the dam wall would reduce flood risk for 130,000 people living in the Hawkesbury-Nepean Valley.

“This strategy is about protecting the lives and property of people who live in the valley, it’s not about facilitating inappropriate development,” he said.

Ayers said alternatives to raising the dam wall had been considered, but this was “the best option to reduce flood risk”.

Brown said a proposal to raise the dam wall had been rejected in the 1990s, and that the only thing that had changed was demand for more housing land in Western Sydney.

“It’s as if there’s no environmental oversight in NSW any more, or certainly none with teeth,” he said.