2014 – Holistic Dam Operations Assessment for Southeast Queensland

Luke Toombes and Rob Ayre

Many large dams are built as multi-purpose structures, providing both flood mitigation and bulk water storage, but requiring a trade-off in functionality between those purposes. In response to the Millennium Drought (2001 to 2009) closely followed by devastating floods in 2011, the State of Queensland initiated a comprehensive review of the operation of its flood mitigation dams. Part of this study involved development of an Integrated Assessment Methodology to provide an informed and unbiased assessment of the competing factors affecting dam operations. The methodology assessed the primary variables of flood damage and other impacts, future bulk water infrastructure and water security requirements in the form of a net present cost/benefit. The study concluded that modification of the dam flood release strategy to reduce flood damage during large events would come at the expense of increased frequency of minor flooding, or vice versa, with minimal net benefit. Similarly, reducing bulk water storage to increase flood mitigation would increase water supply costs by a similar magnitude to the flood damage prevented.