2005 – Prioritising Spillway Upgrades – A Queensland Way

Keith Ehm

SunWater has completed a portfolio risk assessment(PRA) on its 25 major dams and has identified a number of dams that do not currently satisfy the ANCOLD fallback position on spillway capacity. It has taken an initiative to target these dams for spillway upgrades to ultimately achieve the ANCOLD fallback standard and has prioritised these upgrades in a preliminary program for action in the short to medium term.

As background to this PRA, SunWater has developed and implemented a dam safety program which has successfully updated all necessary flood hydrology and dam break analyses and reassessed the consequences and hazards associated with dam failures. It has also completed within the last eight years, dam safety reviews on all its dams in preparation for a comprehensive risk assessment process which is now well in-hand. This process will identify and evaluate all other risks, in addition to floods,that should be addressed or at least considered in the planning and design of these spillway capacity upgrades.

This paper describes SunWater’s experience and approach to PRA and discusses the controlling factors considered in prioritisation. It shows the results and trends of a number of risk ranking methods, provides details of the current level of societal risks in respect of the ANCOLD tolerability limits and outlines SunWater’s current strategy for the timing and staging of spillway upgrades to achieve compliance and an optimum level of risk reduction.

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