The Brisbane River and Flood Risk: Lessons Still Being Learned

Brisbane's relationship with its river has been periodically catastrophic and permanently complex. The 2011 flood, which inundated more than 20,000 properties across the metropolitan area in one of the costliest natural disasters in Australian history, forced a comprehensive reassessment of flood risk management that produced new dam operating guidelines, updated flood mapping, and policies for development in flood-affected areas. The 2022 flood, while less severe, demonstrated that the risk had not been eliminated by these measures.

Wivenhoe Dam's role in both events has been the subject of intense scrutiny. The dam was built as flood mitigation infrastructure following the catastrophic 1974 floods, and its operating manual should guide water releases in ways that minimise downstream flooding. The release decisions in 2011 were examined by a Queensland floods commission of inquiry whose findings generated legal proceedings and ongoing expert debate about optimal dam management under conditions of extreme rainfall uncertainty.

Property development in Brisbane's flood-affected areas has continued despite the flood events, driven by the combination of the locations' amenity advantages, the relative affordability within desirable precincts, and human tendency to discount rare event risks in purchase decisions. The property market does partially reflect flood risk through price discounts for flood-affected properties, but the discount is rarely sufficient to fully price the expected cost of future flood events.

The Brisbane City Council's FloodWise Property Report provides property-level flood risk information to buyers and owners, a transparency measure that was enhanced after the 2011 event. The tool has improved informed decision-making by buyers while creating questions about the extent of the council's duty to act on the risk information it holds, beyond disclosure, in future development approvals.

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