Environmentalists are reeling from the NSW government’s plans to raise the wall of Warragamba Dam by 14 metres.
Keith Muir, director of the Colong Foundation for Wilderness, said plans in the coming NSW Budget to commit to the first phase of the project – at about a tenth of the cost of building the $690 million dam – were a catastrophe.
“There would be significant and obvious damage to world heritage-listed Greater Blue Mountains wilderness and national parks upstream of the dam,” Mr Muir said.
“The lower reaches of protected wild rivers, including the Kowmung, Coxs and Nattai Rivers, would be damaged. Flood inundation will scar wilderness areas by killing river bank vegetation and depositing sediment”, Mr Muir said. He added animals, including wombats and possums, would drown with 3,500 hectares (or 35 square kilometres) turning it into a “dead zone”.
Mr Muir said it was a “cavalier attitude” to the world heritage listing and created “a false sense of security” for those on a flood plain.
“If you allow urban development on a flood plain you are begging for a catastrophe.”
“We need smarter management not a concrete solution. A better solution is to use the capacity of the existing dam for flood mitigation and rely on the auxiliary spillway on the eastern side of the dam wall.”
Premier Mike Baird said plans to raise the wall of Sydney’s Warragamba Dam would significantly reduce the flood risk in the Hawkesbury-Nepean Valley – reducing potential economic impacts from flood risk by about 75 per cent on average.
“The Hawkesbury-Nepean Valley has been identified as having the greatest flood risk in NSW, which poses a serious danger to life and property in western Sydney,” Mr Baird said.
The plan offered “significant extra protection for townships downstream, including Windsor, Richmond and parts of Penrith”.
“This crucial investment is being made so we can reduce the risk to people, animals and property in the event of serious flooding.”
The premier’s office said the decision had come following four years of expert evaluation by the Infrastructure NSW taskforce which had included modelling of thousands of flooding and evacuation scenarios. Modelling had also been conducted by the CSIRO, which simulated over 12,000 road evacuation scenarios across different flood events to help determine the best flood mitigation solution.
An initial $58 million funding will be used in the NSW Budget to do designs, environmental assessments and a business case.The funding will also be used to increase community flood risk awareness, create evacuation signage, improve flood forecasting and integrate the flood risk management with regional planning.
Subject to planning approvals construction is expected to be completed by 2023.
Mr Muir said even with the proposed dam wall raising the other half of Hawkesbury-Nepean’s catchment south of Sydney can produce major floods, as experienced at Picton less than a fortnight ago.
“Big floods from the Grose, Colo and Macdonald Rivers and the South Metropolitan catchments will still affect residential property”, he said.
“The dam wall raising proposal is a half measure, one that creates a false sense of security and probably produce no net gain in public safely.”
He said the dam raising proposal will encourage massive urban sprawl over flood prone areas, putting more people at risk of the floods.
“Urban development on previously flood prone land will further degrade the Hawkesbury-Nepean River from addition urban runoff and sewage discharges. Oyster farmers will also be badly hit by extended fresh water floods from mitigation discharges killing off oyster farms and causing economic ruin,” Mr Muir said.
Mr Muir said the government needed to “respect our international obligations to protect world heritage”. But added it was “something that, like climate change, appears to be of no concern to this current NSW government”.
The Blue Mountains Conservation Society also firmly opposes the raising Warragamba Dam wall.
Vice president Tara Cameron said: "There has been significant concern about the current risks to the Great Barrier Reef and the potential loss of World Heritage status there. Here we have a proposal which would result in 3,500 hectares of the Blue Mountains World Heritage Area being flooded and irrevocably damaged. These parts of the national park will be lost forever, once flooded there is no going back.”
"We are very concerned that between Badgery's Creek airport and raising the Warragamba dam wall, the world heritage values of the Blue Mountains will be deemed at risk by UNESCO. Australia has an international obligation to protect these areas not destroy them. This is an environmental disaster".