The volume-of-fluid (VOF) technique was employed to develop a Computational Fluid Dynamics (CFD) model for comparison to physical measurements available from the Eildon Dam model in Australia for validations purposes. The water surface in the downstream chute of the spillway was observed to be mostly comprised of fully developed aerated flow. The free surface is physically measured as located between the mixing and upper zones, thus investigator judgement is critical to achieve reliable measurements. The mixing zone is also characterized by surface waves to complicate matters even further. A challenge arose to develop a post processing methodology that replicates as closely as possible the measuring technique used by the physical modeller for direct comparison of results, using a novel method which utilises Poisson probability of exceedance applied to the free surface.
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The revised magnitudes of the Geoscience Australia’s NSHA18 earthquake catalogue approximately halve the rate of occurrence of earthquakes of a given Mw magnitude in Australia. This yields probabilistic ground motion levels that are significantly lower than the present design levels at dam sites in Australia that are not near faults, and is expected to result in a general reduction in ground motion levels at dams not near faults estimated for all Risk Assessments, and for Deterministic Assessments for all consequence levels except Extreme Consequence. For the latter, the ANCOLD (2018) guidelines will tend to increase existing SEE ground motion estimates for both of the methods used to estimate the safety evaluation earthquake (SEE). By requiring the use of the Deterministic SEE if it is larger than the probabilistic SEE, and by requiring use of the 85th fractile of the Probabilistic SEE if it is larger than the Deterministic SEE, the ANCOLD (2018) guidelines for Deterministic Assessments are much more conservative than the ICOLD and NZSOLD guidelines for Extreme Consequence dams, especially at those located near faults.
In the face of potential future climate change, it is important that reservoir asset owners and operators consider what such change could mean for the integrity and operations of their assets. This must be developed as an integral part of risk-based management, with a systematic consideration of the uncertain future implications of climate change and their potential consequences.
Systematic assessment of the consequences of potential climate related events/loads should be included as an integral component of a risk-based approach to dam safety management. The magnitude of potential consequences can be used to inform the prioritisation and management responses to these conditions, regardless of probability of occurrence. Designing to accommodate exceedance events is an important response in this process.
The adaptive management process provides a framework within which the implications of uncertain future conditions and risks can be systematically identified and managed, forming the basis of agreeing a defined ‘pathway’ for monitoring and implementation of management actions. The concept of Adaptation Pathways can be utilised for reservoir adaptation, setting out the long-term risk informed process to manage operations and risks.
In 2018, DNRME released the latest revision of the Failure Impact Assessment (FIA) Guidelines and the first significant change since 2003. An FIA is the instrument for determining if a dam is referable and therefore regulated for dam safety purposes in Queensland.
The guidelines reflect upon changes in legislation and advances in methods and tools for assessing consequences of dam failure. The revised version tends to be less prescriptive and emphasises the responsibility of the engineer completing the assessment to develop appropriate and defensible methods.
The paper provides an overview of the FIA guidelines, key concepts, the steps to follow when preparing an FIA and a comparison to ANCOLD’s latest consequence assessment guideline.
Melbourne Water (MW) has historically seen dam safety management as a civil discipline and has focussed on understanding and managing the civil assets at its dam sites. The recent addition of a mechanical engineering resource to the team responsible for the dam safety management has refocused attention on the mechanical and electrical (M&E) assets and provided a more holistic asset management approach to MWs large dams.
This paper discusses the process MW has developed over the past two years to improve their understanding and management of M&E assets. It centres on key process points for how MW has prioritised the development of M&E asset management programs on the basis of an autogenous ‘asset criticality’ rating system and has utilised ANCOLD comprehensive inspections to plan and implement new inspections and tests on dam M&E assets. The two case studies of Sugarloaf and Upper Yarra Reservoirs’ outlet works demonstrate the the benefits of the process to gain operational and technical knowledge of M&E assets, strategic importance to the water supply network, identifying risks therein and reallocate significant funding to address these risks as prioritised by asset criticality.
Oroville Dam is located on the Feather River in northern California (USA). At 234.7 m (770-ft) tall, this earth embankment is the tallest dam in the United States. With its 4.3 billion m3 (3.5 million acre-feet) of storage, Lake Oroville is the second largest reservoir in California, supplying water to cities as far south as Los Angeles. The Oroville Dam, reservoir (Lake Oroville), and hydropower plant facility is the flagship of the State Water Project (SWP), which is owned and operated by the State of California, Department of Water Resources (DWR).