2024 – Operational Flood Forecasting System Requirements for Gated and Nongated Dams for Non-structural Risk Reduction

Richard Mannix, Michel Raymond, David Stephens

Enhanced flood threat detection and warning is a non-structural risk reduction measure for dams with flood induced potential failure modes (PFM) that may be reasonably practicable. The effectiveness depends on the design and operation of flood forecasting and warning systems within a dam safety and operations
context. The authors have observed that forecasting systems are highly varied across Australian dam owners. This paper presents the Dam Flood Engineers’ perspective on good practice requirements of operational flood forecasting systems for dams in order to achieve non-structural risk reduction benefits.

An overview of flood forecasting systems and approaches is provided, including highlighting the key differences between systems for riverine flood forecasting and forecasting for dam operations and dam safety. An approach to objectively quantify flood threat detection and warning time inputs for life loss simulation methods is then presented, followed by an overview of good practice requirements that should be met in order to successfully achieve any risk reduction arising from enhanced flood threat detection and warning arrangements. This paper is the first of its kind in an Australian dam safety context and provides the dams industry with a useful reference in the design and operation and maintenance of flood forecasting systems for dams. The worked example of objectively quantifying lead time enhancement is consistent with guidance in ANCOLD (2022) for assessing non-structural risk reduction measures.