Safety management of dams – the Australian practice3 June 2021
Dr Gamini Adikari and Natalie Kho of SMEC present details on dam safety practice and legislation in Australia
Dam safety guidelines and management programs provide the foresight needed to prevent the disastrous failure of dams. In Australia alone, there are over 500 large dams, with these dams being typically more than 15m high (refer Figure 1). In addition to this, there are an estimated 735,000 small, privately owned farm dams. All these dams give Australia the highest per capita surface water storage of any country in the world, a characteristic necessary given the high aridity of the continent. The safety of Australian dams is managed by a set of best practice national guidelines, with varying levels of legislated regulations undertaken at the state level.
Figure 1. Number of large dams in each Australian State or Territory (ANCOLD, 2012). Solid, multi-coloured segments represent the number of dams owned by individual dam owners (minimum ownership 3 dams). Grey vertical bars represent the number of dams owned by other owners, with less than 3 dams per owner.
National and state-based legislative framework
Australian Dam Safety Guidelines – National Level
The Australian National Committee on Large Dams (ANCOLD), formed in 1937, is responsible for the development and issue of best practice dam safety guidelines at the national level. ANCOLD is the Australian national committee of the International Commission on Large Dams (ICOLD). It is a non-government, non-profit and voluntary association of organizations and individuals with a common technical interest in promoting best practice within the dams industry. As such, guidelines prepared by ANCOLD are published as advisory documents and not legal standards and require the interpretation of experienced professionals when applied to individual dams. This arrangement also allows the guidelines to be adapted to the various administrative legal frameworks of the different states.
There are currently twelve ANCOLD guidelines in print, each focusing on a specific topic. Regarding the safety of existing dams, the most relevant ANCOLD guideline is the ‘Guidelines on Dam Safety Management’, published in 2003. The document identifies methods for identifying who would be affected by dam failure and who should be responsible and involved in ensuring dam safety actions are carried out. It prompts issues that should be considered by dam owners and engineers, which are particularly important when it comes to the prioritization and allocation of limited funds or resources. It also guides the development of dam safety programs for each dam by detailing the expected level and scope of care required, as well as outcomes. The 2003 Guidelines on Dam Safety are intended to provide guidance for management of conventional dams such as those used for water supply, irrigation or recreation. The safety of tailings dams and retarding basins are covered by separate guidelines.
In determining the degree of detail required in dam safety programs, other published ANCOLD guidelines are referred to by the Guidelines on Dam Safety Management. For example, ‘Guidelines on the Consequence Categories for Dams’ provides a consistent quantitative method for classifying dams into consequence categories based on the damage expected should failure occur. This guideline was last updated in 2012, to incorporate the potential loss of life (PLL) thresholds for determination of consequence categories, in addition to the population at risk (PAR).
Other guidelines cover a range of aspects beyond dam safety management, including environmental management and the design of different dam types. Although the guidelines have been prepared for large dams, simplistically defined as dams of at least 10m height, their use is not limited to dams above this height, as the Guidelines can also assist with decision making in the management of smaller dams.
Australian Dam Safety Legal Framework – State Level
Australia is made up of six states and two territories. Five of these states/territories have dam safety regulations – New South Wales (NSW), Victoria, Tasmania, Queensland and the Australian Capital Territory (ACT).
Each of the above five states relies on its own documented regulations (which may refer to or are based on the ANCOLD guidelines) which state in more detail what dam owners must do to be compliant with the legal requirements. In NSW, Tasmania and the ACT, these are documented in specific separate regulations or codes to the acts. The NSW ‘Dams Safety Regulation 2019’ is a recent legislative update, which requires dam owners to comply with state-based regulations and standards, with the ANCOLD Guidelines used to assist in compliance only.
In Victoria, there is an additional focus on a risk management-based approach. This approach is based on a tolerability of risks and demonstration that the level of risk of a dam is ‘as low as reasonably practicable (ALARP)’. Water corporations report annually on the risk profile of their dams and the works undertaken to address these risks, from which the dams can be categorized into five categories of regulatory response. This draws heavily on the ANCOLD ‘Guidelines on Risk Assessment 2003’.
To ensure dam safety compliance, Victoria makes use of dam safety licensing authorities, who work with the state dam safety regulator. In NSW, an independent regulating committee with expertise in dam engineering have the responsibility to investigate and enforce dam safety. The regulator in the other States is typically the ministerial office, with these offices having gone through changes in name and consolidation of responsibilities throughout the years since their inception.
The three remaining states (South Australia, Western Australia), and territories (Northern Territory) are self-regulated. This is because the large dams in these states/territories are largely under the ownership of a single government business enterprise. Legal responsibility is therefore enforceable under the Common Law, requiring dam owners to maintain their assets and prevent failure in a way that shows adequate duty of care.
Figure 2. Dartmouth Dam – the highest earth & rockfill dam in Australia. Photo courtesy of Goulburn-Murray Water.
Figure 3. Scrivener Dam in Canberra, a gated concrete gravity dam which forms the Lake Burley Griffin. Photo courtesy of National Capital Authority.
Dam Safety Programs
Dam owners and dam engineers have different responsibilities in meeting dam safety requirements. The prime responsibility for the safety of the dam rests with the owner. As such, dam owners are responsible for carrying out, and reporting on, the investigation, design, construction, and safety review of their assets. They need to ensure they prepare and update operations and maintenance (O&M) manuals and dam safety emergency plans (DSEP). Dam owners also run monitoring programs to obtain operational and performance data, and commission dam safety inspections. The role of the dams engineer is to support dam owners with their responsibilities, and through their knowledge address technical issues such as regional and site geology, structural soundness, design for all loading conditions, and selection of materials.
In order to achieve the above, dam safety programs incorporate a range of activities to provide, manage, and ensure dam safety. Firstly, a robust dam safety program should provide an overall inspection and monitoring program, as well as clearly defined responsibilities for dams operators, training programs to equip operators with incident management skills, and a system to validate operations and updates. Secondly, any incidents need to be managed by means of a clear plan. Lastly, they should ensure the use of prevailing standards, preventative maintenance as programed, management of risks within tolerable limits, and that appropriate funds and personnel are available. These three aspects are addressed simultaneously, albeit in different ways, by various dam safety activities and processes, as briefly discussed below.
Operation and Maintenance Manuals and Dam Safety Emergency Plans
A dam safety emergency plan (DSEP) is a continually updated set of instructions and maps that deals with possible emergency situations or unusual occurrences at or related to a dam or reservoir. It includes the roles and responsibilities or individuals in an emergency; and procedures for emergency identification, evaluation and notification. These are typically presented in flowchart format for ease of reference during times of duress. It also documents the State Emergency Response Plan (DISPLAN), inundation maps, preventive actions, exercise training and review history.
The efficient and effective management of a dam is enhanced by adopting appropriate Operation & Maintenance (O&M) practices. An O&M Manual is an ideal way to document such practices. The manual typically contains data on the dam such as drawings, operation instructions and procedures, safety surveillance aspects, maintenance schedules and logs.
Dam surveillance is the continuous examination and recording of the condition of a dam and its related structures. Dams are inspection and monitoring is aided by the use of instrumentation which is used to measure parameters such as pore water pressures, seepage flow and movement. The instrumentation data is collected and evaluated, to determine whether deteriorating trends are developing or likely to develop. This also involves review of operation, maintenance and monitoring procedures. The outcomes are reported in surveillance reports. An independent review of the surveillance program is typically undertaken every 5 to 10 years.
Dam Safety Inspections
Dam safety inspections are classified as comprehensive, intermediate, or routine visual, in order of decreasing detail and increasing frequency. The actual frequency at which these inspections are undertaken for different dams is based on the consequence category of the dam as specified in the ANCOLD Guidelines on Dam Safety Management. For example, extreme consequence category dams require 5-yearly comprehensive inspections, annual intermediate inspections and daily routine visual inspections.
Dam safety reports are prepared following inspections to document new findings, changes since previous inspections, and recommendations. They incorporate a review of the dam surveillance and monitoring data, and overall performance. At the comprehensive level, additional detail is required such as an assessment of the dam’s flood handling capacity, statements regarding the safety of the structure against current standards and the adequacy of the dam safety program overall.
Dam Safety Reviews
Dam safety reviews differ from dam safety inspections in that they require the examination of all records and reports of the dam over all available time periods. They are a technical audit in which dam safety is assessed through the investigation and analysis of matters not addressed previously or of items subject to new design criteria or possible deterioration. Further technical information in a dam safety review, in addition to those documented in dam safety reports, includes literature reviews, hydrological/geotechnical/seismological investigations and engineering assessments of specific dam structures. Engineering solutions for defects identified through dam safety reviews can then be developed, designed and ultimately constructed where required.
Dam Safety Risk Assessments
Risk is defined as the likelihood or probability of adverse consequences occurring. Risk assessments consider all possible failure modes, the probability of their occurrence and the magnitude of the consequent adverse event. The risk assessment process involves analyzing and evaluating risks to determine whether existing risks are tolerable (refer Figure 4), and if present risk control measures are adequate. If not, it investigates whether alternative risk control measures are justified for implementation. Dam break simulations are undertaken, leading to analysis of damage and loss of life as a function of probability. Further economic and model sensitivity analysis is also undertaken, leading to recommendations of remedial actions based on acceptable risks.
Figure 4. Example of societal risk guidelines for existing dams (State Government of Victoria, 2014).
The risk-based approach allows remedial actions to be engineering or non-engineering solutions, in contrast to the engineering-focused outcomes in a dam safety review. Non-engineering solutions may involve changes to operating rules or installation of warning systems. Remedial actions can be used to rectify deficiencies but do not imply that no risk remains after the actions are complete. There are always residual risks associated with dam management.
Dam safety risk assessments may be undertaken for a portfolio of dams, or for individual dams. Regardless of the approach, the risk assessment is used to identify critical assets, and act as a planning tool in addressing high risk components by providing a basis for the optimisation of investments and justification of works to stakeholders.
Understanding dam safety in Australia involves considering the ways in which guidelines are set and regulations operate, as well as the strategies and processes adopted by dam owners, aided by dams engineers, to meet these requirements.
- Adikari, G. (2015). Safety Management of Dams - The Australian Practice. Dam Safety Seminar, Melbourne.
- ANCOLD. (2003). Guidelines on Dam Safety Management.
- ANCOLD. (2012). About Us. Retrieved from Australian National Committee on Large Dams Incorporated: https://www.ancold.org.au/
- ANCOLD. (2012). Guidelines on the Consequence Categories for Dams.
- Bradlow, D. D., Palmieri, A., & Salmar, S. M. (2002). Regulatory Framework for Dam Safety.
- D Pisaniello, J. (2011). Big problems for Australia’s small dams. International Water Power & Dam Construction.
- Dams Safety NSW. (2021). Dams Safety. Retrieved from https://www.damsafety.nsw.gov.au/
- McCormick, B. (2019). Water Management. In Parliamentary Library Briefing Book: Key issues for the 46th Parliament. Retrieved from Parliament of Australia.
- Queensland Government. (2019). Dam safety regulations. Retrieved from Business Queensland: https://www.business.qld.gov.au/industries/mining-energy-water/water/industry-infrastructure/dams/safety-guidelines-requirements/regulations
- Southcott, P., & Scott, B. (n.d.). A Review of Australian Dam Safety. International Conference on Dam Safety Management and Engineering, (pp. 606-612).
- State Government of Victoria. (2014). Strategic Framework for Dam Safety Regulation\.
- Tasmanian Government. (2017). Dams. Retrieved from Department of Primary Industries, Parks, Water and Environment: https://dpipwe.tas.gov.au/water/dams