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Urban Rivers is not necessarily a term that we use in Australia but the 2023 New Zealand Rivers Group Conference was a valuable theme. A perspective that some rivers have been built over, around or through in the development of our towns and cities. Often without fully understanding the geomorphological tendencies of the river system or the
flood risk across the floodplain posed by the catchment. Managing urban rivers for flood control has led to some unintended consequences. Residual Risk and Unintended Consequences The way to manage urban rivers is to not create them in the first place. This means in the limited cases where we have greenfield development we need to make room for the river, mindful of the geomorphology and flood risk. Where we choose to engineer the river’s course or mitigate risk we create a financial management, asset management and risk management burden in perpetuity. Maybe this is acceptable. Given we typically engineer to a design standard that is less than the Probable Maximum Flood we are inherently accepting some level of residual risk. A risk that is passed to the community (without their acceptance), disaster managers (with finite capacity) or the insurance industry (which is
proving less and less likely to be a viable/guaranteed option). Infrastructure renewal, climate change, changing societal expectations are causing a rethink in urban river management. This is an exciting time in urban river management. Cities are turning to face their rivers. In
the Southeast of Queensland we are seeing this in poster projects like the Norman Creek Master Plan (including Coorparoo Creek daylighting and more recently Hanlon Park) in Brisbane as well as Slacks Creek in Logan and many others. Recovery and Need What is needed: Advocacy (for funding and change), guidance (National Standards underpinning investment) and (adaptive) trigger levels are needed. Presently many local Councils in NZ are investing in recovery without guaranteed financial support from the Central (Federal) government. Drawing on future reserves to repair and rebuild roads, infrastructure and to make
safe their towns and catchments which have experienced devastating erosion and landslides. Currently there is disparate funding for recovery and resilience with no single central government agency responsible for support and funding. The “Reconstruction” model legislated in
Queensland and New South Wales linked with Disaster Recovery Funding Arrangements may be a model worth exploring. There is a clear and present need to address the gap in recovery arrangements (to prevent extended recovery) and I hope that this can be addressed in the near term. The theme of “care or fear” The Keynote Speaker Prof. Ian Rutherford concluded that “To live with our rivers we have to care for them. Not fear them.” This theme reappeared throughout the conference, especially in relation to community resilience and engagement. With regard to engagement, passionate discussion
highlighted the need to engage with our community including traditional owners. We can either fear the conversation or care to start the conversation. It may not be easy but we (the flood industry) need to start talking more about flood risk. There is deep-seated trauma and
distrust from traditional owners towards authorities. This is paralleled by those communities that have been dramatically impacted by major and catastrophic flood events of recent times. We (government and the industry) need to rebuild that trust (and it was noted that is not ‘transactional’ but is a commitment and a dedication to work together moving forward). Planning with uncertainty in mind Development in high risk areas of the floodplain and subsequent flood modification (structural mitigation/levees) are proving unsustainable in larger, more intense, more frequent rainfall events. This is creating a
need for managed retreat. Again reinforcing that the 1%AEP is the building standard (without considering risk - including risk in events larger than the 1%AEP, risk multipliers, community vulnerability and risk tolerability) particularly in flash flood catchments, is not going
to be a high enough standard to mitigate flood risk to a tolerable level in the future climate. Personally, I think this is an area that we need to do better in Australia. The dynamic and rapidly evolving understanding of our changing climate and flooding behaviour means we are
falling short when it comes to planning with uncertainty associated with design flood estimation and Shared Socio-economic Pathways (SSP) for climate change. And if we are short of the mark when it comes to planning with uncertainty, then we are a long way short when it comes to communicating uncertainty (subject for a future article perhaps). Thanks Thank you to the NZ Rivers Group organising committee for hosting Floodplain Management Australia and delegates across the industry. I take many learnings back to Australia and I will definitely return - maybe with a paper next time! Will Prentice FMA Queensland Director
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