CONOLLY SUPPORTS RAISING THE WARRAGAMBA DAM WALL
Written on the 3 May 2018 by Kevin Conolly
Member for Riverstone, Kevin Conolly MP spoke in parliament this week about the NSW Government's proposal to raise the wall of the Warragamba Dam by 14 metres.
Much of the Riverstone electorate lies within the floodplain of the Hawkesbury-Nepean river system and this river system presents the greatest flood risk in New South Wales due to the number of lives at risk, the depth and velocity of water likely to be experienced, and the potential damage to homes and infrastructure.
During his speech Mr Conolly explained further how the Warragamba Dam is built and how it works now, explaining that this design means that the raising of the wall cannot lead to increased permanent water storage. This debunks one of the inaccurate arguments used by Greens and others to oppose the project.
"Some people may imagine a dam with a spillway at the topthe sort of dam that holds back water until it reaches the top of the wall and then spills over. But that is not how Warragamba Dam is built or is designed to work. If one looks at a photograph of Warragamba Dam as it is currently, one will see that it has five gates set in the wallnot at the top, but part-way up. These are like windows in the dam wall. Four of the five gates are operated by dam controllers, but the fifththe gate in the centre, known as the drum gateis opened automatically by the weight of water pushing against it."
The proposal is to raise the wall of the dam above the flood gates, without altering the height of the flood gates. Just like in the 1990s, when the wall was raised by a smaller amount, the "windows" in the dam wall would stay just where they are, so no addition to the permanent storage level would occur.
Mr Conolly went on to say,
"If water were to rise so much that it overtopped the wall, it would create a real risk that the dam wall would break. This could happen when the amount of rainwater entering the dam from upstream exceeded the amount of water that could pass out through the five gates, even when fully open."
The wall raising is designed to save lives, homes, businesses and public infrastructure all of which would be at risk in a major flood. The costs to the community which would be caused by such a flood, in terms of public infrastructure alone, are far greater than the cost of undertaking this project.
For a complete record of Mr Conolly's speech please refer to the Hansard extract attached.
Author: Kevin Conolly
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