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Kate Robilliard, Kristen Sih

The As Low As Reasonably Practicable (ALARP) principle was established in the Australian Dams
community in the ANCOLD Guidelines on Risk Assessment in 1994. Since that time, dam owners have been focused on reducing their societal risk to below the ANCOLD Limit of Tolerability (LoT) through dam safety upgrades and are now considering how to justify an ALARP position. This paper presents a framework that provides a systematic approach to assembling the inputs, applying a process and documenting the outcomes of an ALARP assessment. It is a pragmatic approach that aligns with the safety case, which is a legislated requirement for Major Hazard Facilities in Victoria.
The framework has been applied to two dams in Melbourne Water’s portfolio with differing societal risk, size, uses and criticality to the water supply system. It has highlighted the importance of dam safety governance, documentation of procedures, defensible technical analysis and an ongoing engagement with leading industry practice, in demonstrating risks are ALARP.

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2018 Papers

2018 – A Logical ALARP Risk Procedure
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Kate Robilliard, Kristen Sih

The As Low As Reasonably Practicable (ALARP) principle was established in the Australian Dams
community in the ANCOLD Guidelines on Risk Assessment in 1994. Since that time, dam owners have been focused on reducing their societal risk to below the ANCOLD Limit of Tolerability (LoT) through dam safety upgrades and are now considering how to justify an ALARP position. This paper presents a framework that provides a systematic approach to assembling the inputs, applying a process and documenting the outcomes of an ALARP assessment. It is a pragmatic approach that aligns with the safety case, which is a legislated requirement for Major Hazard Facilities in Victoria.
The framework has been applied to two dams in Melbourne Water’s portfolio with differing societal risk, size, uses and criticality to the water supply system. It has highlighted the importance of dam safety governance, documentation of procedures, defensible technical analysis and an ongoing engagement with leading industry practice, in demonstrating risks are ALARP.
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2018 Papers

2018 – A Quick Probable Maximum Flood Estimation Method for Queensland
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Samantha Watt, Michael Hughes & Daniela Sciacca

This paper presents an updated simplified technique for estimation of extreme floods in Queensland. This technique will be of use to practicing hydrologists and engineers working on early phase investigations of dams, weirs, and other infrastructure that requires flood resilience for extreme floods. The equations presented in this paper will provide practitioners with a robust yet simple to apply technique to rapidly estimate peak PMPF and PMF flows (inflows for dams) for Queensland catchments. This will assist feasibility and optioneering of infrastructure without significant cost overheads associated with often complex and time-consuming extreme flood estimates.
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2018 Papers

2018 – A Robust and Efficient Stochastic Simulation Framework for Estimating Reservoir Stage-Frequency Curves with Uncertainty Bounds
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C. Haden Smith

The U.S. Army Corps of Engineers (USACE) Risk Management Center (RMC) developed the Reservoir Frequency Analysis software (RMC-RFA) to facilitate, enhance, and expedite flood hazard assessments within the USACE Dam Safety Program. RMC-RFA is a stochastic flood modeling software that employs advanced statistical and computing techniques, allowing a user to perform a screening-level stage-frequency analysis on a desktop PC with runtimes on the order of seconds to a few minutes. RMC-RFA utilizes an inflow volume-based stochastic simulation framework that treats the seasonal occurrence of the flood event, the antecedent reservoir stage, inflow volume, and the inflow flood hydrograph shape as uncertain variables rather than fixed values. In order to construct uncertainty bounds for reservoir stage-frequency estimates, RMC-RFA employs a two looped, nested Monte Carlo methodology. The natural variability of the reservoir stage is simulated in the inner loop defined as a realization, which comprises many thousands of events, while the knowledge uncertainty in the inflow volume-frequency distribution is simulated in the outer loop, which comprises many realizations.

Stage-frequency curves derived with RMC-RFA are compared to those derived with more complex, precipitation-based simulation frameworks, such as the Monte Carlo Reservoir Analysis Model (MCRAM), the Stochastic Event Flood Model (SEFM), and the Watershed Analysis Tool (HEC-WAT). The inflow volume-based framework employed by RMC-RFA produces stage-frequency curves that strongly agree with the more complex, precipitation-based methods. Furthermore, the results from the alternative methods fall within the RMC-RFA uncertainty bounds, demonstrating its robustness. In this sense, the RMC-RFA simulation framework lends itself to a value of information approach to risk management, where knowledge uncertainty can be efficiently quantified at a screening-level assessment, and then the value of performing more complex and sophisticated studies to reduce uncertainty can be considered.
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2018 Papers

2018 – Advanced InSAR Techniques for Remote Monitoring of Dam Stability
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Jessica Morgan

Regular assessment of dam stability is essential to ensure safe and reliable operation of these structures throughout their service life. In some cases, monitoring of the surrounding environment can be as important as monitoring carried out over the dam itself. Risk management programs should therefore look at the entire site and nearby terrain to ensure any and all possible geohazards which may impact dam integrity are identified and tracked over time.

InSAR is a type of remote sensing that uses radar satellite imagery to measure surface movement occurring over time, often achieving millimetric levels of precision. This approach does not require fieldwork or the installation of equipment, measurements are instead obtained from reflections of the satellite radar signal off infrastructure, rocks and bare ground. Furthermore, as the measurements are obtained from satellite images that extend over regions thousands of kilometres squared in size, they can provide information on stability over dams, surrounding reservoirs, even entire regions.
The main advantage of InSAR technology for dam monitoring is two-fold. First, in addition to monitoring the dam itself, stability of the surrounding area (including slopes around dam reservoirs) can be tracked. Second, both long- and short-term displacement trends can be captured (including historical analyses) providing a more complete picture of dam behaviour over time.

Several examples of InSAR results obtained over different dam sites are presented.
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2018 Papers

2018 – Advances in the Automation of Population at Risk Quantification for Dam Failure Consequence Assessment
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Matthew Scorah

Population at Risk (PAR) estimation involves quantification of people who could be exposed to flooding in the event of a dam failure. Conventionally, estimates of PAR involve manual and subjective assessment of individual structures located downstream of dams. To reduce the reliance on subjective judgement and better leverage publicly available population datasets, an automated method of PAR assessment was developed. This approach used the Geoscape dataset of building representations to disaggregate Australian Bureau of Statistics 2016 Census data for a study area around Gawler, South Australia.

Representative day and night spatial distributions of PAR were constructed to characterise the diurnal movement of people between homes and workplaces or other day activities. Flows of people were directly quantified to reduce reliance on high level assumptions regarding exposure. A Random Forest model was used to filter sheds and other unpopulated structures from the Geoscape dataset.
The largest deficiency in this approach is the lack of high detail data to classify building usage. It is recommended that the potential for automation of PAR assessment be continually revisited as more datasets become available.
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2018 Papers

2018 – ANCOLD Proceedings of Technical Groups 1 Dam Safety Decision Making
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Jane Branson,, Kelly Maslin, Samantha Watt, Chriselyn Kavanaghah

Since publication in 2003, the ANCOLD Guidelines for Risk Assessment have reached broad acceptance and use in Australia. In practice, dam owners use the principles of risk assessment to drive business investment decisions. As the guidelines undergo revision, it is timely to assess whether our practices need to evolve to more holistically consider all types of consequences, rather than our current focus on loss of life, in decision-making. This paper aims to prompt dam owners and consultants alike to re-assess our focus on loss of life in risk assessment decision-making, and whether we should more meaningfully consider alternative or broader indicators.

An industry survey was undertaken which found that large dam owners are generally happy with the current system of dam safety decision making. However, the survey responses did identify difficulties in relation to justifying investment below the limit of tolerability that are subject to ALARP principles. In a small number of cases, dam owners found it difficult to justify investment when life safety was not important.

Building on the industry survey and subsequent discussions with practitioners, this paper discusses how the current approach to risk based decision making may result in sub optimal decision making. Further it is discussed how there is an important role that economics should play in providing a universally accepted framework for assessing trade-offs and providing consistent evidence to support decision making.
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2018 Papers

2018 – Ash Tailings Dam Rehabilitation – Challenges and Aspirational Targets
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Stafford Griffiths

The rehabilitation of wet tailings storages is likely to become of increasing importance. In a setting of increasing environmental regulation and oversight, the environmental issues inherent in wet tailings storages will increase in visibility. This will translate through to increased regulatory attention, rehabilitation standards and costs. This scenario will necessitate increased engineering ingenuity and approaches to develop cost effective and robust/ defensible outcomes.

This case study of a coal fired power station ash dam rehabilitation compares a conventional (baseline) rehabilitation strategy and the development of a higher land use, with potentially beneficial outcomes for the owner, the community and the environment.

The baseline rehabilitation was a conventional fit-for-purpose rehabilitation approach consistent with the proposed final land use comprising the creation of a stable, open greenspace environment. The higher land use was an aspirational target style rehabilitation, with the assessed highest and best use for the site that was determined to be an industrial land development. While there will be limitations due to the low strength tailings foundation, this higher land use is considered an appropriate stretch target and is a feasible outcome for this site.
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2018 Papers

2018 – Assessing the Accuracy of a Two-Dimensional Hydraulic Model for Dambreak Analysis
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Daniel Sheehy, Dr Sharmil Markar, Dr David Newton

Two-dimensional hydraulic modelling technology has advanced significantly in recent years, providing powerful and flexible tools that are now routinely used for a wide variety of flood risk assessments. Assessing the downstream impacts of catastrophic dam failure represents an extreme test for the accuracy and stability of hydraulic models. Catastrophic dam failure can present an extreme risk to downstream infrastructure and public safety. Hence, it is important to have confidence in the estimated magnitude of potential impacts to design suitable, costeffective mitigation measures. The highly visual output of two-dimensional models adds credibility to their results. However, validation data for extreme hydraulic conditions is rarely available, resulting in uncertainty in the accuracy of model predictions and in the risks associated with dam failure. By validating numerical model results against analytical solutions for cases of simple geometry and also against realworld data, an improved level of confidence can be obtained in the accuracy of the model representation of these extreme hydraulic conditions. In this paper, we assessed the capability of the TUFLOW hydraulic modelling software package to accurately simulate an idealised dam break scenario by comparing the model results to analytical solutions. We also compared the model results for coastal inundation by a tsunami to real-world data from the 2004 Banda Ache (Indonesia) tsunami. The results showed that the HPC solver version of TUFLOW correctly captures the dam break flood fronts and the flood wave propagation and TUFLOW HPC is well suited for dam break flood modelling.
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2018 Papers

2018 – Comparison of EZ-FRISK and OpenQuake Seismic Hazard Programs
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Elodie Borleis, Russell Cuthbertson

There are a number of software packages that have been developed to conduct Probabilistic Seismic Hazard Assessments (PSHA’s). Each one has advantages and disadvantages. Two such programs are compared; the licenced subscription-based EZ-FRISK software package developed by Fugro USA Land, Inc. and the open-sourced OpenQuake-engine (OQ) software package by the Global Earthquake Model (GEM) Foundation. Both of these packages use the classical PSHA methodology as described by Cornell (1968) and modified by McGuire (1976). Each of these packages offers different advantages; OQ is freely distributed, code based and provides easy access to a number of tools. EZ-FRISK doesn’t rely on command-line tools and instead provides an easy user interface with quick access to plots to check results. EZ-FRISK is computationally faster than the OQ program.

A simple rectangular source model with four sites was used to investigate the degree of agreement between these two software packages. Results indicate that hazard estimates from the two packages agree to within 4% for the two closest sites. At long return periods for the two furthest sites, the difference is larger.
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2018 Papers

2018 – Comparison of Pore Pressures Obtained from Saturated and Unsaturated Finite Element Analyses with Monitoring Data
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Meysam Safavian, GHD

This paper will explore the differences in pore pressures resulting from saturated and unsaturated seepage (pore pressure) analysis. It will also evaluate some conventional recommendations, such as the inclusion of essential components of the embankment dam and omission of inessential components. In addition, the identification of inessential components will be discussed.
Finally, pore pressures obtained from these analyses will be compared to monitoring data in order to identify the most appropriate seepage (pore pressure) model.
In conclusion, advantages and disadvantages of each method will be discussed and recommendations will be provided in order to gain the most appropriate results.
The results of this paper can be used for designing new embankment dams or safety reviews of existing dams, particularly when there is lack of reliable monitoring data.
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2018 Papers

2018 – Controlling the Murray River – Electrical and Control System Upgrade works at Yarrawonga and Torrumbarry Weirs
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Paul Seaward, Chee Woo, Trevor Lange

Yarrawonga and Torrumbarry Weirs; located on the Murray River bordering Victoria and New South
Wales, are operated by Goulburn Murray Water on behalf of the Murray Darling Basin Authority.
The electrical and control systems that operate both structures were nearing 20 years of age, resulting in risk associated with equipment nearing the end of its useful working life and hardware obsolescence, driving this upgrade program. These control systems are critical in the monitoring and management of river levels and flows that extensively affect Victorian and New South Wales irrigation supplies and recreational users on the Murray River and Lake Mulwala.

Considerable effort was required to update and develop the control philosophy before proceeding to the design phase of the projects. The requirement to work on these brownfield sites, while maintaining operational ability and minimising dam safety and water delivery risks, resulted in a significant implementation and commissioning process. During the course of these works, the opportunity was also taken to enhance and update remote monitoring capability.

The lessons learnt on these projects are being incorporated into current Electrical and Control System Upgrade projects at Cairn Curran Reservoir and Dartmouth Dam.
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2018 Papers

2018 – Current Australian and International Practices for Dam Failure Consequence Assessments
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Simon Lang

Many Australian and international dam owners use risk assessments to understand and manage the societal risks posed by their dams. This requires estimates of dam failure consequences, particularly the potential loss of life (PLL). The methods used to assess PLL have become more varied and sophisticated in recent times. This paper summarises the current status of the methods most relevant to the Australian dams industry (i.e. RCEM, HEC-LifeSim, the Life Safety Model), and comments on their applicability for Australian PLL assessments. This commentary is based on material presented by dam owners, regulators, researchers and consultants from the United States, Canada, United Kingdom and the Netherlands, at workshops on estimating dam failure consequences held in Denver in 2016 and Toronto in 2018.
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2018 Papers

2018 – Dam Safety Decision Making
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Jane Branson – Principal Economist, Jacobs Australia, Kelly Maslin – Executive Director of Operations – Southern, Jacobs Australia, Samantha Watt – Associate, Jacobs Australia, Chriselyn Kavanagh – Senior Surface Water Engineer, Jacobs Australia

Since publication in 2003, the ANCOLD Guidelines for Risk Assessment have reached broad acceptance and use in Australia. In practice, dam owners use the principles of risk assessment to drive business investment decisions. As the guidelines undergo revision, it is timely to assess whether our practices need to evolve to more holistically consider all types of consequences, rather than our current focus on loss of life, in decision-making. This paper aims to prompt dam owners and consultants alike to re-assess our focus on loss of life in risk assessment decision-making, and whether we should more meaningfully consider alternative or broader indicators.
An industry survey was undertaken which found that large dam owners are generally happy with the current system of dam safety decision making. However, the survey responses did identify difficulties in relation to justifying investment below the limit of tolerability that are subject to ALARP principles. In a small number of cases, dam owners found it difficult to justify investment when life safety was not important.

Building on the industry survey and subsequent discussions with practitioners, this paper discusses how the current approach to risk based decision making may result in sub optimal decision making. Further it is discussed how there is an important role that economics should play in providing a universally accepted framework for assessing trade-offs and providing consistent evidence to support decision making.
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2018 Papers

2018 – Dam Safety Management of Junction and Clover Dams: A Risk Based and Observational Approach
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Steven O’Brien, Christopher Dann, Timo Mantyvirta

Junction and Clover Dams are central spillway slab-and-buttress dams located in Victoria. Previous safety reviews and assessments of the dams concluded that neither dam met modern dam design standards and remedial works were recommended, including infilling the slab-and-buttress dams with mass concrete to sustain seismic loadings. These conclusions were based largely on the assessed seismic hazard at the site, the results of response spectrum analyses and observed conditions of the dams including alkali-aggregate reaction of the concrete. AECOM used current seismic hazard assessment techniques, conducted concrete investigations and testing, assessed long term surveillance monitoring results and used modern finite element techniques to demonstrate that no upgrade works were required at either dam resulting in a significant saving for AGL.
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2018 Papers

2018 – Demonstration of HEC-LifeSim Analysis of Dam Failure
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Tyson Leong-Cuzack, Rhys James, Robert Fowden, Chris Nielsen

An assessment of dam failure consequence for Jandowae Water Supply Dam in South-West Queensland was performed using HEC-LifeSim. The purpose of the assessment was to investigate the applicability of the software to inform decisions on an appropriate regulatory pathway for the dam that reflects the consequences of failure. This paper details the development of the hydrologic and hydraulic models behind the HEC-LifeSim simulations, the assignment of key parameters and their sensitivities, and a comparison of predictions to existing procedures for assessing potential loss of life and populations at risk. The paper reflects upon the level of effort required to develop HEC-LifeSim assessments and the relative benefits gained using this information in the regulatory space.
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2018 Papers

2018 – Design and Construction of Ulu Jelai Reservoir Rim Stabilisations
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James Martin, Nash Kobarajah

Ulu Jelai project is a recently completed 372MW hydroelectric peak – power project located in the Cameron Highlands of Malaysia. A combination of power generating and reservoir operating conditions together with the site topography, existing road infrastructure, geology and hydrogeological conditions pose a significant risk to the viability of the project during operation. As a result, significant reservoir rim stability treatments were designed and constructed along a 3.5km section of the right abutment of t he Susu Reservoir to reduce the risk of instability to acceptable levels. This paper describes the methods of investigations, stability assessment and design aspects of the reservoir rim stability treatments that were constructed.
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Search Results: “” — Page 1

Kate Robilliard, Kristen Sih

Kate Robilliard, Kristen Sih

Samantha Watt, Michael Hughes & Daniela Sciacca

C. Haden Smith

Jessica Morgan

Matthew Scorah

Jane Branson,, Kelly Maslin, Samantha Watt, Chriselyn Kavanaghah

Stafford Griffiths

Daniel Sheehy, Dr Sharmil Markar, Dr David Newton

Elodie Borleis, Russell Cuthbertson

Meysam Safavian, GHD

Paul Seaward, Chee Woo, Trevor Lange

Simon Lang

Jane Branson – Principal Economist, Jacobs Australia, Kelly Maslin – Executive Director of Operations – Southern, Jacobs Australia, Samantha Watt – Associate, Jacobs Australia, Chriselyn Kavanagh – Senior Surface Water Engineer, Jacobs Australia

Steven O’Brien, Christopher Dann, Timo Mantyvirta

Tyson Leong-Cuzack, Rhys James, Robert Fowden, Chris Nielsen

James Martin, Nash Kobarajah