The dam raising is being driven by developer interests on the Hawkesbury-Nepean floodplain. The NSW Government has stated in its principle document advocating the dam proposal that it plans to allow an additional 134,000 people to reside on western Sydney floodplains after the dam is raised [i].
Infrastructure NSW map showing planned development areas on the Hawkesbury-Nepean floodplain [ii].
There have been numerous inappropriate western-Sydney floodplain developments green-lighted in 2017/18 (the same year legislating to raise the dam was rammed through the NSW Parliament). These include the Penrith Panthers, Penrith Lakes, Marsden Park North and Vineyard development proposals. The SEPP for a number of these areas allows for development below the 1:100 year flood planning level [iii]. International best practice dictates that floodplain development should not occur below the 1:500 year level [ix].
Minister Ayres, the Minister for Western Sydney has himself said that he plans for future development across the low-lying Penrith floodplain "as far as the eye can see" in the coming years [x].
The Western Sydney Leadership Council's chairman, Christopher Brown, has flagged developing flood-prone land as a potential funding source for the dam wall extension [xi], saying:
"I think there's the capacity to use a value-capture funding method to reduce the impact on taxpayers," he said.
"Maybe via levy on land release that was previously considered flood-prone so we might be able to do it at a cheaper rate than what the Government's talking about."
[i] Infrastructure NSW (2017), Hawkesbury-Nepean Valley Flood Risk Management Strategy, page 3. Available online: https://bit.ly/2wDd4VL
[ii] Molino Stewart (2012), Hawkesbury-Nepean Flood Damages Assessment, Prepared for Infrastructure NSW, page 15. Available online: https://bit.ly/2MXahcH
[iii] Environmental Planning and Assessment Act 1979, State Environmental Planning Policy (Penrith Lakes Scheme) Amendment 2017, page 19. Available online: https://bit.ly/2PrXwrT
[ix] Caroline Wenger, Karen Hussey & Jamie Pittock (2012) The Use of the 1:100 Year Standard in the United States: Insights for Australia? Australian Environment Review, Vol. 27, pages 337-342
[x] Channel 9 News (2014) 4th of December 2014 News Coverage of Penrith Lakes. Available online: https://bit.ly/2EpcaPu
[xi] Sarah Gerathy (2016) Warragamba Dam: Wall Flood-Protection Plan Raises Environmental Concerns, Australian Broadcasting Company. Available online: https://ab.co/2G8np0E