Deformation Survey is a simple and widely implemented technique to identify the early signs of dam failure and is regularly undertaken on many dams. Thanks to advances in equipment and more accurate survey records, there is now a better understanding of measurement and movement of embankments and previous records.
However, the “expected” range of transverse deformation and implications for failure modes of dams is not particularly well researched or understood.
This paper collates a case history of transverse deformation for a number of Tasmanian dams and examines the relative behaviour of the embankment dams. From this the “expected behaviour” of an embankment dam can be estimated and related to key influencing factors, such as observed settlements, height and age of the dams, and thereby providing guidance on when transverse deformation is considered unusual for similar dams.
Regular assessment of dam stability is essential to ensure safe and reliable operation of these structures throughout their service life. In some cases, monitoring of the surrounding environment can be as important as monitoring carried out over the dam itself. Risk management programs should therefore look at the entire site and nearby terrain to ensure any and all possible geohazards which may impact dam integrity are identified and tracked over time.
InSAR is a type of remote sensing that uses radar satellite imagery to measure surface movement occurring over time, often achieving millimetric levels of precision. This approach does not require fieldwork or the installation of equipment, measurements are instead obtained from reflections of the satellite radar signal off infrastructure, rocks and bare ground. Furthermore, as the measurements are obtained from satellite images that extend over regions thousands of kilometres squared in size, they can provide information on stability over dams, surrounding reservoirs, even entire regions.
The main advantage of InSAR technology for dam monitoring is two-fold. First, in addition to monitoring the dam itself, stability of the surrounding area (including slopes around dam reservoirs) can be tracked. Second, both long- and short-term displacement trends can be captured (including historical analyses) providing a more complete picture of dam behaviour over time.
Several examples of InSAR results obtained over different dam sites are presented.
An assessment of dam failure consequence for Jandowae Water Supply Dam in South-West Queensland was performed using HEC-LifeSim. The purpose of the assessment was to investigate the applicability of the software to inform decisions on an appropriate regulatory pathway for the dam that reflects the consequences of failure. This paper details the development of the hydrologic and hydraulic models behind the HEC-LifeSim simulations, the assignment of key parameters and their sensitivities, and a comparison of predictions to existing procedures for assessing potential loss of life and populations at risk. The paper reflects upon the level of effort required to develop HEC-LifeSim assessments and the relative benefits gained using this information in the regulatory space.
Two-dimensional hydraulic modelling technology has advanced significantly in recent years, providing powerful and flexible tools that are now routinely used for a wide variety of flood risk assessments. Assessing the downstream impacts of catastrophic dam failure represents an extreme test for the accuracy and stability of hydraulic models. Catastrophic dam failure can present an extreme risk to downstream infrastructure and public safety. Hence, it is important to have confidence in the estimated magnitude of potential impacts to design suitable, costeffective mitigation measures. The highly visual output of two-dimensional models adds credibility to their results. However, validation data for extreme hydraulic conditions is rarely available, resulting in uncertainty in the accuracy of model predictions and in the risks associated with dam failure. By validating numerical model results against analytical solutions for cases of simple geometry and also against realworld data, an improved level of confidence can be obtained in the accuracy of the model representation of these extreme hydraulic conditions. In this paper, we assessed the capability of the TUFLOW hydraulic modelling software package to accurately simulate an idealised dam break scenario by comparing the model results to analytical solutions. We also compared the model results for coastal inundation by a tsunami to real-world data from the 2004 Banda Ache (Indonesia) tsunami. The results showed that the HPC solver version of TUFLOW correctly captures the dam break flood fronts and the flood wave propagation and TUFLOW HPC is well suited for dam break flood modelling.
This paper describes taking the data from the transducer recording of dynamic fluctuations at 300 Hz in the physical hydraulic model of the stilling basin of Fairbairn dam and analysing the response of the proposed design solution to these loads. The analysis not only looked at the direct time history loading, but reviewed the response of the anchoring system to the inertial and damping loads. A further extension of the analysis allowing for the stiffness of water has come up with some findings that verify what has intuitively been believed about the design of spillway stilling basin slabs.
The volume-of-fluid (VOF) technique was employed to develop a Computational Fluid Dynamics (CFD) model for comparison to physical measurements available from the Eildon Dam model in Australia for validations purposes. The water surface in the downstream chute of the spillway was observed to be mostly comprised of fully developed aerated flow. The free surface is physically measured as located between the mixing and upper zones, thus investigator judgement is critical to achieve reliable measurements. The mixing zone is also characterized by surface waves to complicate matters even further. A challenge arose to develop a post processing methodology that replicates as closely as possible the measuring technique used by the physical modeller for direct comparison of results, using a novel method which utilises Poisson probability of exceedance applied to the free surface.