Floodplain Manager October 2021


It was 30 years ago that I first became involved in floodplain management when I was given the task of researching and developing methodologies for estimating some of the potential flood damages which could occur in the Hawkesbury Nepean Valley. It was also a year after a significant flood on the river. A few years later I was project managing the EIS for a flood mitigation proposal at Warragamba Dam and within a couple of months of establishing Molino Stewart the EIS was printed ready for release.

At that time there was a change in State Government, the decision was made not to build a mitigation dam and the EIS was never placed on public exhibition (although 400 copies went out the door in response to freedom of information requests). I was disappointed, not that the dam did not proceed, but that there had been no vigorous public debate about the issues before that decision was made.

There are significant environmental values upstream of the dam which would be impacted when flood waters are detained in the mitigation storage but also social and economic impacts downstream which its operation would significantly reduce. Yet it is not as simple as upstream environment versus downstream economy. A mitigation dam would protect some downstream environmental values but would also cause some downstream economic losses.

The State Government at the time said that instead of relying on a mitigation dam, the downstream flood impacts to people and property would be mitigated by emergency planning and urban planning. While much has been done to improve emergency planning and evacuation infrastructure in the Hawkesbury Nepean Valley, the planning controls applied in the most vulnerable parts of the Valley have meant that new development has outstripped evacuation route upgrades.

The current NSW State Government has decided to revisit the issue of flood mitigation at Warragamba and an EIS is currently on public exhibition. This is one part of a nine-point strategy to deal with flooding in the Valley. Emergency planning and urban planning are two other important points in that strategy. However, this time there has been a concerted effort to make the community more aware of the flood risks, with community education being another strategy plank. The floods in March of this year, the first of any significance since 1990 and much smaller than many others which have been recorded, are a reminder that the flood risks are real and must be dealt with one way or another.

Whatever decision is made about the dam, there will be environments, communities and individuals that may be worse off and those that may be better off. For this reason, I am hoping that this time around that there is public, rigorous and participated debate about the issues, so that an informed decision can be made. While it is not an easy decision, I am hoping it is not simply a politically expedient one.


Steven Molino


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