G. Hadzilacos, ML. Ng, K. Taske, A. Small and B. Loney
Alteration of flow patterns by constructing a dam may have an irreversible impact on ecosystems depending on the timing, duration and frequency of these flows. As part of an Environmental Impact Study, carried out for a proposed mining operation in Australia that included an earth dam on a pristine ephemeral creek, an appropriate waterway management scheme was proposed that required the establishment of measurable instream flow requirements. This paper describes an environmental flow analysis (EFA) carried out to identify flow regimes that achieve the desired ecological outcomes for the affected waterways. The EFA methodology was based on the range-of-variability approach using a calibrated rainfall-runoff model to form the hydrologic basis. The study established a relationship between flow components and ecological variables based upon which the flow requirements were estimated using a simple methodology.
2011 – A case study of an initial Environmental Flows Assessment for an earth dam on a pristine stream in Cape York
This paper provides the insight of one practitioner into the process and application of Dam Safety Risk Assessment. The ANCOLD Guidelines on Risk Assessment provide a reasonably comprehensive outline of the key tasks involved in the risk assessment process. The intent of this paper is not to rehash the Guidelines but rather to discuss some of the practicalities of completing a dam safety risk assessment and highlight some key learning’s gained from a wide range of projects for a number of different owners.
The paper includes a brief overview of each component of the risk assessment process as well as some of the advantages and disadvantages of the various approaches to completing a risk assessment project.
2011 – Dam Safety Risk Assessment – A Practitioner’s Perspective
B. Ghahreman Nejad, H. Taiebat, M. Dillon and K. Seddon
One of the causes of tailings dam failure has been seismically induced liquefaction during earthquakes. Liquefaction, if mobilised, significantly reduces the stiffness and strength of affected soils in the embankment dam or its foundation and may lead to large deformations and dam failure. This paper reports the results of seismic liquefaction assessment and deformation analyses of Bobadil tailings dam located in Tasmania. The tailings dam consists of a perimeter rockfill starter dam which has been raised in stages using the “upstream” construction method. The embankment raises (formed by clay or coarse tailings) are constructed over a foundation of previously deposited tailings in the impoundment which is potentially susceptible to liquefaction. Extensive field and laboratory tests were carried out to assess the tailings liquefaction potential and also to determine the material properties required for seismic stability and deformation analyses. Numerical modelling of seismic liquefaction and deformation analyses were carried out to predict the magnitude and pattern of deformations that may lead to uncontrolled release of tailings. The results of these analyses are presented and compared with literature report of those observed during past earthquakes.
2011 – Numerical Modelling of Seismic Liquefaction for Bobadil Tailings Dam
Dan Forster, Murray Gillon
A robust and defensible dam surveillance process is considered to be the ‘front-line of defence’ in ensuring dams do not present an unacceptable risk to people, property and the environment. The concept of a ‘Quality Chain of Dam Surveillance’ describes the surveillance process as a multi-linked chain where each step in the process forms a critical link. Without rigorous attention given to quality assurance links in the chain can become tenuous or broken and thus compromise the integrity of the whole chain. Hydro Tasmania is currently re-engineering its existing surveillance process using the Quality Chain of Dam Surveillance as a basis.
This paper presents the concept of the quality chain and uses the Hydro Tasmania improvement initiative as an example application of the concept. The paper is intended to provide a fresh perspective on what is sometimes considered a stale topic and reinforces the need for a considered approach to dam surveillance.
2011 – The Quality Chain of Dam Surveillance
Stuart Richardson,Tusitha Karunaratne
Goulburn-Murray Water (G-MW) manages 16 large dams across Northern Victoria. Since January 2010 after 10 years of continuous drought a number of significant and historic maximum floods were passed through some of these dams. Although these floods are not considered extreme in a dam safety context, for downstream communities they presented very real emergency situations. There has been significant community concern regarding the impact of the floods resulting in several inquiries.
G-MW has maintained and annually reviewed comprehensive Dam Safety Emergency Management Plans (DSEP) since 1997. During 2009 G-MW began developing and documenting a systemised approach to dam’s management, operation and emergency response by developing and integrating its Operations and Maintenance Manuals, Flood Incident Management Plans and Dam Safety Emergency Management Plans. The plans have been developed to align with the Australian Inter Service Incident Management System (AIIMS) which G-MW uses as its corporate incident response framework.
This paper provides an overview of the benefits of having structured and integrated manuals and response plans for managing assets, flood and extreme events. The paper also shares G-MW’s experiences in developing this integrated management approach.
Workshop paper – Karunaratne 2011 – Management of Floods in 2010 and 2011 through Goulburn-Murray Water Dams
The large flood inundating areas of Brisbane and Ipswich along the lower Brisbane River below Wivenhoe Dam in January 2011 was extensively reported by the media. An independent Commission of Inquiry was formed soon after the flood with broad terms of reference including matters related to dam operations. Prior to the Inquiry hearings and findings, reporting in the media continued and made strong allegations of blame of the flood on dam operations. The media relied on limited expertise but the articles were portrayed and subsequently re-produced by other media outlets as ‘expert’ analyses. The author’s interpretation is that media claims were misleading and damaging to the public confidence in the role of dams for flood mitigation, and this damage occurred before official Inquiry findings were available.
A brief summary is presented of now publicly available credible reports on the flood event, and a summary is also presented of the key matters and allegations reported in the media related to the dam operations. An analysis and commentary of media reporting on the flood operations of the Wivenhoe Dam is presented in the context of time and people with reference to information and expertise available to the media, and media conduct in relation to fair public interest and professional practice.
Matters of importance for objective and informed knowledge of key technical matters in relation to operation of dams, dam safety, and the inevitable extremes of nature and floods are discussed. The paper then examines the roles and possible limitations of dams engineering professionals in relation to media reporting of such matters.
This paper solely focuses on matters of media examination of the floods and dam operations, and generally does not comment on technical matters that are in the terms of reference of the Commission of Inquiry.
2011 – January 2011 Brisbane River Floods and Examination by Media of the Dam Operations