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P.I. Hill, D. Cook, R.J. Nathan, P.A. Crowe, J.H. Green, N. Mayo

This paper describes the development of a comprehensive approach to estimating the consequences of failure of a dam. The approach considers separately the consequences in terms of potential loss of life, economic loss and damage to the environment and the development and application of the method involved professionals from a wide range of disciplines. The method has been applied to 28 dams in NSW.

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2000 Papers

2000 – Development of a Comprehensive Approach to Consequence Assessment
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P.I. Hill, D. Cook, R.J. Nathan, P.A. Crowe, J.H. Green, N. Mayo

This paper describes the development of a comprehensive approach to estimating the consequences of failure of a dam. The approach considers separately the consequences in terms of potential loss of life, economic loss and damage to the environment and the development and application of the method involved professionals from a wide range of disciplines. The method has been applied to 28 dams in NSW.
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2014 Papers

2014 – Advances in Portfolio Risk Analysis for Improved Management of Dam Safety Risk – a State Water Perspective
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Andrew Richardson, Stephen Farrelly and Phil Farnik

In 2012 an update to the Portfolio Risk Analysis (PRA) was undertaken by State Water Corporation for its 18 major dams in New South Wales. The updated portfolio level risk analysis of all the dams has taken account of the completion of major components of the 2006 dam safety upgrade program, while also incorporating continued engineering research into dam safety performance. This paper will provide an overview of the approach, the challenges faced in the process and it will highlight the innovative advances made representing industry best practice. Some future implications and directions will also be discussed.

The three main components of the PRA update in 2012 have included a significant amount of dam break hydraulic modelling including revised hydrology and flood inundation mapping delivered in-house by State Water with consultant support. The Consequence Assessment was developed with a spatial link to natural flooding and dam failure consequences by Sinclair Knight Mertz (SKM), while the third element in producing the event trees, risk analysis and PRA reports was undertaken by consultants GHD. Peer review of the PRA process and reports and additional technical review of the failure modes and event trees by a panel of industry experts provided the necessary independent input and oversight required by the NSW Dams Safety Committee.

State Water’s PRA update builds on the large body of work undertaken for and since the last PRA in 2002. The update process has applied a systematic and quantitative approach across the Portfolio that provides a robust basis for managing dam safety risk. The results of the PRA have identified further work required to investigate and assess the need for dam safety upgrade options for non-compliant dams. State Water’s investment in the PRA has produced a risk-based position on each dam in the portfolio that can be used to identify a range of measures in a revised dam safety upgrade program for the future.

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2017 Papers

2017 – Impact of Detailed Consequence Assessment on Leslie Harrison Dam Upgrade Works
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Peyman Andaroodi, Barton Maher

Seqwater is a statutory authority of the Government of Queensland that provides bulk water storage, transport and treatment, water grid management and planning, catchment management and flood mitigation services to the South East Queensland region of Australia. Seqwater also provides irrigation services to about 1,200 rural customers in the region that are not connected to the grid and provides recreation facilities. Seqwater owns and operates 26 referable dams regulated under Queensland dam safety legislation.

Leslie Harrison Dam is an Extreme Hazard category dam located in the Redland Bay area of Brisbane.A significant portion of Population at Risk is located within a short distance downstream of the dam, reducing the available warning time in the event of a dam safety issue and impacting on the estimated loss of life used to assess risk. Following the Portfolio Risk Assessment undertaken by Seqwater in 2013, a series of detailed investigations were undertaken to confirm the assessed risk and the scope and urgency of the upgrade works.

Before a final decision on the scope and timing of the dam upgrade is made, Seqwater has completed a detailed review of the downstream consequences. This review was intended to update the Population at Risk(PAR) and Potential Loss of Life(PLL) estimates using the latest estimation methods for a range of scenarios. Three life loss estimation methods were used including empirical and dynamic simulation models and the results were compared.

This paper discusses the updated consequences assessment and the impact on the assessed risks, for Leslie Harrison Dam for both the current dam and the proposed upgrade scenarios using the revised Potential Loss of Life estimates.
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2017 Papers

2017 – Tailoring Consequence Assessments for Retarding Basins
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Andrew Northfield, Simon Lang, Peter Hill

Melbourne Water currently manages more than230retarding basins (RBs). A large portion of these are less than 4 metres high, and traditionally structures of this size have not been subject to intermediate or detailed ANCOLD Consequence Assessments. However, the need to understand the failure consequences for smaller structures has increased over time, as risk based approaches to managing safety have expanded from large dams to other water retaining assets.

Undertaking detailed consequence assessments for all Melbourne Water’s RBs would not be practical, given the costs and time involved. Therefore, this paper describes a method for assessing the level of ANCOLD Consequence Assessment that is justified, based on the structure’s attributes. It also presents an equation that was used to estimate peak outflows from RB failure. The peak outflow estimates can be used to model approximate failure inundation extents downstream of small dams and RBs.

The paper draws on work that HARC have recently undertaken for Melbourne Water to assess the failure consequences for 88 RBs. The outcomes are relevant to other organisations that own or manage significant numbers of small water dams or RBs.
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2018 Papers

2018 – Using HEC-LifeSim to Better Understand and Reduce Dam Failure Consequences for Three Case Studies Around Australia
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Hench Wang, Andrew Northfield, Peter Hill

HEC-LifeSim modelling has been emerging in the industry over the last few years and is increasingly becoming the preferred method for detailed consequence and failure impact assessments. The increased adoption rate of HEC-LifeSim modelling is a result of advancements to computation power and hydraulic modelling techniques and allows dam owners to obtain more robust and consistent estimates of the potential loss of life (PLL) compared to the traditional Graham (1999) and RCEM (USBR, 2014) approaches.

This paper will demonstrate, through the use of three examples, how the inputs and outputs from HEC- LifeSim have been used to identify potential ways to better understand the consequences as a result of dambreak.
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2019 Papers

2019 – Lessons Learnt From Evacuation Modelling for Dam Failure Consequence Assessments
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Hench Wang

The use of simulation models to assess dam failure consequences has progressively advanced in Australia over the past few years. For example, it is now common for HEC-LifeSim to be used to estimate potential loss of life from the failure of large dams with large populations at risk downstream. Since its introduction to Australia, numerous presentations and papers have been provided by USACE and industry professionals that highlight the benefits of using HEC-LifeSim for a range of different case studies.

Whilst the majority of the literature published to date have focused on the benefits of simulation modelling, this paper identifies some of the technical challenges that can arise, particularly in the evacuation modelling component of HEC-LifeSim. The techniques that have been used to overcome these challenges are also discussed using three case studies.

The first case study demonstrates the sensitivity of the life loss to changes in cell size and the output interval of the gridded hydraulic data. This is done by comparing the differences in life loss between high-resolution and low-resolution models for three dambreak models. The second case study illustrates the importance of the road network representation in HEC-LifeSim because the resolution of the road network is important to achieve plausible estimates of the fatalities along roads, and logical animations of the mobilisation. The final case study demonstrates the implications of coincident flow modelling on the life loss, and therefore the importance of understanding the hydrology of the target and neighbouring catchments.

This paper provides a checklist that prompts practitioners to consider some of the lessons learnt over the last few years and is envisaged to be a working document that improves the defensibility and robustness of HEC-LifeSim estimates throughout the industry.
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2020 Papers

2020 – Demonstrating risk benefits of improved monitoring and surveillance
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Hench Wang, Peter Hill, Sam Banzi, Muhammad Hameed

Dam owners can often struggle to demonstrate the dam safety risk benefits that can be achieved through non-structural risk reduction measures, such as adoption of smart technological solutions that improve the timeliness and quality of decision making. WaterNSW collaborated with HARC to develop a novel way of demonstrating benefits from improved data management. This paper discusses the use of HEC-LifeSim to demonstrate the reduction in life safety risk from improved monitoring through DamGuard for a case study dam in Sydney. DamGuard is a real-time dam safety monitoring system implemented by WaterNSW. This case study was the first time in Australia where a simulation model such as HEC-LifeSim was applied to quantify the life safety risk benefits pre and post the implementation of DamGuard. The implementation of DamGuard to the sample dam was estimated to reduce the life safety risk by 15%.
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2021 Papers

2021 – Common Ground – Baselining Consequence Assessments in downstream catchments
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Rachel Jensen, Adam Broit, Chriselyn Kavanagh

Downstream emergency response is a critical driver in the consequences and potential life loss associated with dam flooding and failure. This response is highly varied between stakeholders, communities and the nature of the flooding or dam threat. As assessments on dam failure consequence and potential loss of life become increasingly important in understanding holistic dam risk, they are also becoming increasingly complex.

As part of a portfolio wide Comprehensive Risk Assessments, Sunwater have undertaken workshops with a wide range of stakeholders to better understand downstream emergency response and the warning timeline. The workshops have been aimed at facilitating better downstream stakeholder engagement, obtaining key data for consequence assessments and developing consistency in assumptions for potential life loss.

This paper presents the standardised methodology undertaken for warning time workshops, the outcomes for a range of downstream stakeholders and correlations between stakeholder groups which influence warning time response. These outcomes may be used by practitioners in the absence of catchment specific warning time data and provide a counterpoint to international standard warning time assumptions.
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2021 Papers

2021 – Lessons learnt from the application of HEC-LifeSim 2.0 to multiple dams across Australia
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Hench Wang, Edward Funnell, Albert Shen, Matt Scorah, Peter Hill

The use of simulation models to assess dam failure consequences has progressively advanced in Australia over the past few years. For example, it is now common for HEC-LifeSim to be used to estimate potential loss of life from the failure of large dams with large populations at risk downstream. Since its introduction to Australia, numerous presentations and papers have been provided by USACE and industry professionals that highlight the benefits of using HEC-LifeSim Version 1.0.1 for a range of different case studies.

This paper identifies some of the new features in the latest version of HEC-LifeSim that can improve the robustness and defensibility of the potential loss of life estimates for dambreak consequence assessments. The techniques that have been used to overcome these challenges are also discussed using some case studies.

The first case study demonstrates the sensitivity of the model performance and potential loss of life to changes in version and number of iterations used to simulate the life loss. This is done by comparing the differences in simulation run time and life loss between the previous and new versions of HEC-LifeSim for an example model. The second case study presents an example application of both versions of HEC-LifeSim to compare the results between one version and the other for a different dam and the final case study illustrates an improved method for interrogating the available outputs from HEC-LifeSim to provide the user with more information that otherwise could not be obtained from the default outputs.
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2021 Papers

2021 – Managing multiple concurrences estimating likelihood and consequence in dam break application, Rainfall based data sparse regions
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Claudia Smith, Shannon Dooland, Adam Broit, Rachel Jensen, Samantha Watt

The estimation of real consequences from dam failure that directly link to the overall likelihood of the failure is a challenging task, particularly in data sparse locations. Previous regional methods have often relied on simplistic assumptions without consideration of the true joint probability of the volume of flow in the downstream tributaries of concurrent catchments. As a result, concurrent downstream flooding directly impacting the consequence in dam break assessment scenarios may be misrepresented. More recently, the adoption of streamflow-based joint probability has become the standard, particularly where consequence estimation is used within the context of risk assessment. This paper progresses the work completed by others to establish a practical treatment method based on rainfall analysis where suitable streamflow information is unavailable. A case study is also presented where this method has improved the understanding of the risk profile associated with a coastal storage based on a better estimate of the likely flood concurrence within the storage and downstream catchments.
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2012 Papers

2012 – Development Of A Comprehensive Approach To Portfolio Consequence Assessment Using Spatial Data
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A.E. Bentley, P.I. Hill, S.M. Lang, M. Freund, A. Richardson

This paper describes the development of a detailed assessment approach using spatial data to estimate the consequences of dam failure across a portfolio of 18 dams in NSW. The assessment is made for potential loss of life; economic and financial losses and a qualitative assessment of environmental and social impacts. The approach is designed around the use and interrogation of spatial databases combined with outputs from hydraulic models. The assessment method is applicable to a wide range of dams in different valleys, each with different downstream characteristics. The paper provides discussion on the advantages of the approach and presents some insights into the effective application to a dam portfolio of significant size and scale.
Keywords: consequence assessment, spatial databases
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2012 Papers

2012 – Applying joint probabilistic techniques to the determination of downstream coincident flows and incremental consequences of dam failure
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David Stephens, Peter Hill, Rory Nathan

The estimation of incremental consequences of dam failure often requires consideration of coincident flows in downstream tributaries. In the past overly simplistic assumptions have often been adopted. Examples include an assumption that flows in downstream tributaries are negligible, equivalent to the 1 in 100 Annual Exceedance Probability (AEP) flood, the mean annual flood or the flood of record. Experience has shown that these assumptions often underestimate coincident flows, particularly for extreme events approaching the AEP of the Probable Maximum Precipitation. Additionally, the justification for adopting these techniques is usually driven by ease of use rather than the degree to which they represent the relevant physical processes at play. For some dams, these techniques may have a negligible influence on the overall consequence assessment. However, there are many dams for which an improved understanding of coincident flows using a joint probabilistic framework can result in significantly altered estimates of the natural flood and dambreak flood inundation zone. This can frequently lead to the consequences of the natural flood being larger than would otherwise have been the case, leading to a reduction in incremental consequences. Two examples of such situations are presented, including a description of the techniques used to estimate coincident flows and a discussion on likely influence of these flow estimates on incremental consequences. These examples are then used to draw some general principles for the types of dams at which an improved understanding of coincident flows is warranted.
Keywords: dam failure, coincident, joint probability, consequence assessment
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2009 Papers

2009 – Today’s Capital, Tomorrow’s Consequences; Assessing Future Failure Costs
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Alice Lecocq, Bob Wark, Paul Hurst, Michael Somerford

The justification for dam safety remedial works is often based on an assessment of life safety risk and financial losses defined at a discrete point in time. However these parameters are likely to change over time with demographic growth, land and industrial development. The Water Corporation has a number of dams upstream of major growth areas and an understanding of the future direct and indirect economic consequences of dam failure are required in order to define the change in risk profile over time.

This paper outlines the study framework adopted by the Water Corporation to review its capital expenditure on its remedial works programme. Dam failure consequence assessments for Wellington, Serpentine and Samson Brook Dams are presented and the paper describes the methodology adopted to forecast the likely development within the inundation areas. A framework to consistently estimate future changes to life safety and economic consequences is also presented.

Keywords: demographic growth, land and industry development, monetary assessment, future trends, consequence assessment.
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Search Results: “” — Page 1

Hench Wang, Andrew Northfield, Peter Hill

Hench Wang