K.A. Crawford-Flett, J.J.M. Haskell
Dam inventories can provide a comprehensive understanding of a region’s dam population; from dam quantity, type, age, height, and purpose; to ownership profiling and broad-based regional risk assessment using GIS applications. Historically, New Zealand has lacked a comprehensive inventory of dam assets, instead relying on local and industry knowledge to characterise the dam infrastructure and its key properties, issues, and risks.
This paper presents a cross-sectional characterisation of dams in New Zealand, based on the recent compilation and analysis of a New Zealand Inventory of Dams (NZID). The NZID is the first inventory of its kind for NZ dams, comprising almost 1200 unique structures over 3 m in height. Inventory data was sourced from existing publications, NZSOLD, and regional authorities. The analysis of anonymised inventory data provides an understanding of the number and distribution of assets, along with characteristic physical properties (construction material, height, age, purpose).
Statistical comparisons are drawn in relation to published international dam inventories. Similarities and differences in the international dam populations are noted, particularly with regard to construction era and type. The NZ portfolio is unique in that dams are typically shorter in height, and a significant proportion of structures serve the hydroelectric and energy sectors.
Analysis of the new NZID confirms the need for research that is focused on the long-term performance of aging earth dams, particularly those exceeding 40 years of age. In addition to informing research needs and foci, the new NZID provides statistics on the dam population with far-reaching industry and management applications
Dr Matthew Sentry, Nabeel Elias
Although permanent ground anchor technology has advanced in leaps and bounds over the past two decades, the focus of anchor technology has been on developing techniques to minimise the risk of component and system failure due to corrosion. The advancements in structural materials available in the market in recent years have enabled research into alternative materials for permanent ground anchor systems.
Carbon fibre has become a significant structural alternative throughout North America for bridge and building construction as well as repair and structural strengthening of deteriorated/corroded structures. These advancements and the necessity to investigate alternative materials for anchor systems have led to research in understanding the long term performance effects of using carbon fibre products as an alternative to steel tendons in permanent ground anchors.
Following on from the advanced research works at Monash University and Geotechnical Engineering which investigated the durability performance of various available CFRP strands when used as an alternative to conventional steel tendons in permanent ground anchor systems, Geotech developed the first post tensioned ground anchor system using CFRP strand.
Following laboratory based trials and small scale bun barrel tests, Geotech was able to successfully design, construct, install and stress the first 27 strand post tensioned CFRP ground anchor installed into Yass Dam. The CFRP strand was stressed and locked off at 4,000kN. Real time monitoring has been installed to monitor the load throughout the anchors service life.
This paper provides the details of the construction, installation and stressing of the first CFRP anchor installed into a dam structure.
Assoc. Prof. Shu-Qing Yang
Next to air, freshwater has been always considered as a key resource, central for economic development and human’s basic needs. Currently the total population is about 7 billion, and by 2050, global population is projected to be 9 billion. An additional 10 more Nile Rivers are needed, and the water demand is increasing steadily and significantly. The dams industry has successfully solved the water deficit problems in many places for most of the time, but more and more countries and regions are gradually resorting to other emerging technologies like desalination, wastewater recycling and rainwater tanks etc. as they believe that a dam is the 20th century technology and has too many significant negative impacts. However, available data show that the global water consumption is only 5~6% of annual runoff, e.g., Australia’s water use is about 20km3, but the runoff lost to the sea is up to 440km3. A coastal reservoir is a freshwater reservoir inside seawater, aimed at the development of freshwater from the sea without desalination. The 1st generation of coastal reservoir has emerged in China, Singapore, Hong Kong and Korea successfully, but generally its water quality is not as good as that in inland dams. The 2nd generation of coastal reservoirs has been developed and its water quality is at least comparable with the water in existing reservoirs like Warragamba dam. The application of coastal reservoirs in Australia is discussed and the feasibility is investigated. The preliminary designs of coastal reservoirs in SE Queensland, Sydney, Melbourne, Adelaide and Perth show that the coastal reservoir is a feasible and effective technology for Australia’s water crisis.
Jason Needham, John Sorensen, Dennis Mileti, Simon Lang
The potential loss of life from floods, including those caused by dam failure, is sensitive to assumptions about warning and evacuation of the population at risk. Therefore, the U.S. Army Corps of Engineers engaged with social scientists to better understand the process of warning and mobilizing communities that experience severe flooding. This improved understanding enables dam owners to better assess the existing risk posed by their assets and investigate non-structural risk reduction measures alongside structural upgrades.
In this paper, the U.S. Army Corps of Engineers research is summarised to provide general guidance on the warning and mobilization of populations at risk for practitioners assessing the potential loss of life from dam failure. This includes commentary and quantification of three primary timeframes: warning issuance delay, warning diffusion, and protective action initiation. A questionnaire for estimating these parameters is also introduced, alongside a case study application for an Australian dam.
This paper also summarises the current understanding of how to reduce delays in determining when to issue warnings, increase speed at which warnings spread through communities, and decrease the time people spend before taking the recommended protective action. These insights will help all people involved with emergency management, including those tasked with developing Dam Safety Emergency Plans.
D Stephens and P Hill
Dambreak modelling and consequence assessment is a key component of many dam safety related studies. The outputs from these assessments can be used to inform the consequence category, dam safety emergency planning, risk-based surveillance and dam safety risk assessment. These studies are complex, intensive and expensive to complete, and all too often there is a need to manipulate or extrapolate the results of these assessments to fit a purpose other than what they were intended for. This issue is particularly prevalent for risk assessment, where the likelihood calculations are directly tied to analysis of the key failure modes, but consequences may be taken from previous studies which were not informed by failure mode selection. The result of this mismatch may lead to inefficiencies and uncertainties in preparing the risk estimates. Subtle changes to the timing or scope of the original dambreak modelling and consequence assessments, at relatively small incremental cost, may help to prevent these issues arising for future studies. Advice is provided on specific issues such as the determination of the downstream extent of the dambreak modelling, selection of the dambreak modelling scenarios and reconciliation of the consequence assessment results with flood and seismic loading partitions for risk assessment. It is hoped that the advice provided will lead to an overall increase in the efficiency and value for money of these studies.
Amanda Ament, Thomas Ewing, Frank Nitzsche
The automatic operating buoyancy type spillway gates at Lenthall Dam did not operate properly since installation. This paper discusses the problems encountered, the investigation conducted using computational fluid dynamics to quantify the problems and develop solutions. It describes the design of the modifications to the gate and flow regime and results after construction.