2009 – Ross River Dam Upgrade – Flood Commissioning Experience

Rob Ayre, Simone Gillespie, Peter Richardson, Mark Harvey

In November 2007, NQWater (now Townsville City Council) completed the upgrade of Ross River Dam near Townsville. This upgrade included the installation of a Program Logic Control (PLC) operated radial gate structure in the existing spillway. The purpose of the upgrade was threefold; to meet current design standards regarding dam safety and flood capacity; increase the town water supply to Townsville and Thuringowa; and to maintain the flood mitigation benefit of the dam during flood events in the Ross River catchment.

The designers of the dam upgrade completed a risk assessment at the commencement of the design phase and concluded that a PLC operated gated dam posed less risk than an approach that relied purely on dam operators. This is seen as the “new way forward” in gate operated dams by many designers. The regulator of dam safety in Queensland has indicated a preference for an operator to remain on site full time whilst the PLC system is ‘proved’. As a consequence a flood operations team was engaged to monitor the dam during times of flood through the commissioning period of the upgrade.

This paper discusses the lessons learnt from the experiences of the Ross River Dam during its first few flood events and issues associated with the adopted design approach.

Keywords: Dam Safety, Gated Spillway, Flood Operations, Ross River Dam, NQWater, Townsville City Council, SunWater, Queensland.

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