Dam safety issues and the case for regulation in South Australia: a discussion paper
Date
2016
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Pisaniello, J.
Tingey Holyoak, J.
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Dam safety is a critical issue for South Australia and yet dam safety regulation has not been implemented in the state. This is despite many devastating dam failures globally and the recognised need for dam safety assurance in other states in Australia and in many jurisdictions around the world. This Discussion Paper is designed to inform the deliberations of the Flood Reform Taskforce with respect to dam safety risk, legislation and policy and the case to be made for regulation development and implementation in South Australia. he paper firstly presents the existing regulatory arrangements in South Australia, other Australian states and overseas, including examples. This includes benchmarking of dam safety regulations and presentation of minimum to best practice models. Secondly, the paper presents the magnitude of risk currently posed by dam failure in South Australia, including numbers of dams, the amplification of flood risk, and demonstrative case study, empirical and comparative evidence of the risk. Currently, legislative arrangements in SA are such that certain dam development applications are assessed under the Development Act 1993 (SA) and under the NRM Act 2004 (SA) the Natural Resources Management (NRM) Boards have some control over dam capacity within specified catchment and zone interception limits for water allocations. But neither Act provides for assessment of how a dam is designed or constructed with regard to safety risk, nor any ongoing supervision to ensure dams are maintained properly during their life. Hence, lastly there is consideration of how dam regulation can be used to manage public risk and improve dam safety in SA. The paper finds that the risks exist at various inter-related levels and the necessary policy response is three-fold as follows:1. The dam failure flood risks are significant and exist at both the individual and cumulative levels within catchments. Evidence presented indicates that between 70 - 90% of hazardous private dams have highly inadequate spillway flood capabilities (many not capable of passing even a 1-in-100 year event) and/or other structural dam safety problems, representing unacceptable individual dam failure flood risks. Cumulative failure of numerous dams can exacerbate flooding in catchment basins and also give rise to higher risk of failure of large public dams, e.g. Kangaroo Creek Dam which may be vulnerable to failure from only a 1-in-200 year event. Therefore, need dam safety assurance policy per the policy models and guidelines presented. Best practice policy is appropriate for SA, but at least minimum practice is an essential starting point. 2. The safety risks are inter-related with water equity risks due to the ‘dual-extreme cumulative threat’ phenomenon: i) exacerbation of droughts during times of limited rainfall due to unfair storage of water in dams, and ii) exacerbation of floods during extreme rainfall caused by unsafe water storage in dams. Because spillway capacity/height effects the storage/yield capacity of a dam, and over 70% of spillways are blocked and/or under-designed, there needs to be integration of dam safety policy with water equity policy.3. The safety risks are linked to land development risks and so need to be accounted in land use planning policy. Two scenarios exists: (1) new dam developments above existing communities and (2) new community developments below existing dams causing ‘hazard creep’. Therefore, need appropriate integration of dam safety policy with land use planning policy.The following general recommendations are provided for SA policy makers:1. Established minimum and best practice assurance benchmarks should be integrated into policy for safe catchments; 2. A supervisory system should be implemented to plan, design, review and maintain dams according to acceptable safety practice in line with the benchmarks and Australian National Committee on Large Dams (ANCOLD) guidelines; 3. Within this system most dams, but especially those that could pose either considerable individual or cumulative hazard, need registration and regulatory control, and spillway flood capabilities should be particularly in focus. 4. The system should be fit-for-purpose (ie simpler, cheaper obligations for low hazard dams and increasingly more stringent requirements for higher hazard dams) and include provision of inexpensive safety design/review and monitoring solutions, such as the Tasmanian simple proforma for smaller, less hazardous dams, the Victorian user-friendly hazard/consequence screening tool, and the cost-effective flood safety tool presented.Specific options for South Australia include: 1. Providing for legislation via amendments under the Natural Resources Management Act (2004). This would facilitate empowering an existing authority to regulate and supervise dam safety such as in Victoria or Tasmania, and integrate this legislation with both water sharing/allocation policy and land use planning policy similar to the Tasmanian system, or 2. Establishing a specific dam safety Act. Establishing an authority, similar to the NSW approach, but providing for a more extensive supervisory remit and integration with other relevant policies, or3. Establishing a model of average practice in the immediate term. This at the very least provides for the minimum level benchmark which includes owner education and guidance, registration of dams and mandating of Emergency Action Plans for all hazardous dams. An average practice model may also include mandatory insurance and/or only selected elements of strict ‘command and control’ dam safety regulation such as Victoria’s system of only licencing dams over 5 m height and 50 ML storage or 10 m height and 20 ML storage as well as those recognised as high hazard under ANCOLD guidelines. If after 5 years the situation has improved enough within the benchmarked criteria presented, then policy can remain with the average practice model as a substitute to best practice, otherwise there is a need to move up to the best practice model.Any such dam safety regulation in SA would have significant benefits, including ensuring:• the design of the dam is commensurate with its hazard, ie, the greater the consequences of failure, the higher the standard the dam needs to be designed for. This includes both structural design and capacity of the spillway;• ongoing maintenance of dams so their original design standards are maintained. This is not just making sure spillways remain clear and are adequately designed, but also checking for signs of structural damage and movement, erosion, management of vegetation;• for high hazard dams, dam owners undertake dambreak assessment and prepare emergency action plans (including monitoring and communication arrangements) so that the government can be adequately informed and prepared in case of an emergency; and• a database of hazardous dams is established which would contain information critical for emergency response. From an emergency management perspective currently, (with the exception of SA Water reservoirs) there is very poor understanding of where hazardous dams are, which ones could be at risk of over topping, what the impacts would be if they did, and where and if it may be necessary to evacuate people.The paper concludes with the above recommendations for potential policy action as well as possible additional research to further substantiate such action.
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Copyright 2016 the Authors