South East Queensland Water Corporation (SEQWater) as owner and operator is proceeding with an upgrade of the flood capacity of Wivenhoe Dam. SEQWater has formed an Alliance with Leighton Contractors, Coffey Geosciences, Montgomery Watson Harza (MWH) and the Department of Commerce-NSW (formerly DPWS, NSW) to upgrade Wivenhoe Dam. This paper presents feasibility level investigation and design activities for an upgrade option, comprising a large labyrinth auxiliary spillway at the right abutment of the dam, for supplementing the existing gated spillway in handling the Probable Maximum Flood (PMF) event. This right abutment auxiliary spillway option incorporates Hydroplus type concrete fuse gates. The investigation so far has proved the technical viability of this option, however, ranking along with the other three options against various criteria will lead to the selection of the preferred upgrade option.
Phillip Jordan, Rory Nathan, L. Mittiga1 M. Pearse, and Brian Taylor
There are many important dams and other structures on catchments smaller than 1000 km² with response times less than 24 hours, however these catchments have been largely overlooked in previous research into large and extreme floods. This paper is an initial step in “catching up” design practice for short duration rainfall events to the current best practice that is available for estimation of floods from rainfall events with durations of 24 hours and greater.
Two issues are specifically addressed in this paper. Firstly, a regional analysis of short duration rainfall depths is conducted to extend the frequency curve beyond an AEP of 1 in 100. Rainfall frequency curves are estimated for durations between 0.5 and 12 hours, using data from ten pluviograph sites around Australia. Secondly, sets of temporal patterns are derived that could be useful in joint probability analysis of short duration rainfall events. The effects of these new rainfall depths and temporal patterns on flood frequency curves are tested by applying them to rainfall-runoff routing models for three dams with small catchment areas.
Many dam structures in Australia were designed and built in the 1950s and 60s with limited hydrological information. As a result existing spillway structures are under-sized for today’s revised probable maximum floods (PMF). Potential problems such as the generation of excessive negative pressure over spillway crest under increased flood condition could be encountered. This may cause instability or cavitation damage to the spillway. The raised flow profile may also have adverse impacts on crest bridges and gate structures.
Historically, physical models have been constructed in hydraulic laboratories to study these behaviours, but they are expensive, time-consuming and there are many difficulties associated with scaling effects. Today, with the use of high-performance computers and more efficient computational fluid dynamics (CFD) codes, the behaviour of hydraulic structures can be investigated numerically in reasonable time and expense.
This paper describes the two- and three-dimensional CFD modelling of spillway behaviour under rising flood levels. The results have been validated against published data and good agreement was obtained. The technique has been applied to investigate several spillway structures in Australia.
To allow greater flexibility in their generation and hence a better response to the peaks in electricity demand, Southern Hydro decided to increase the Full Supply Level of Dartmouth Regulatory Dam by 3.5m using labyrinth Fusegates.
The Regulating Dam is located on the Mitta Mitta River, approximately 8 km downstream of Dartmouth Dam. It is a 23 m high concrete gravity structure with a 60 m long central spillway section. The dam forms the storage required for regulating releases from the Dartmouth Power Station back to the Mitta Mitta River, so as to satisfy environmental requirements.
Although this is the second Fusegate project in Australia it is unique in that difficult access conditions determined that construction in mild steel would be the most appropriate. Initial civil works involved construction of a flat sill to replace the Ogee spillway crest so that it could support the Fusegates. The installation contractor devised an ingenious method for installing the huge structures over the top of the gate-house which blocks direct access to the spillway. Design was very much undertaken with the installation method in mind to ensure a high quality project with minimum contractual risk.
This paper discusses the construction stage of this very interesting spillway modification.
This paper discusses reliability issues of the fourteen 3.85m high by 7.89m wide radial gates at Glenmaggie Dam in Victoria and the twin 3.6m high by 16.5m wide drum gates at Little Nerang Dam in Queensland. The Glenmaggie dam radial gates are manually controlled using electrically driven (mains and diesel generator power supply) hoist motors with a petrol driven hydraulic pack for use in the event of complete electrical power supply failure. A detailed fault tree analysis was developed for the spillway gate reliability of the Glenmaggie Dam gates as part of the risk assessment for the dam, which was being completed at the time of publishing the paper. Each of the identified components of the spillway gates, including human error in operation was used to evaluate the probability of failure of a single gate or multiple gates for inclusion in the event tree to estimate the risk and assist the evaluation of the requirement for remedial works. The Little Nerang drum gates are fully automatic hydraulically operated gates with independent operating mechanics and a common override system in the event of automatic system failure. Drum gates are uncommon on dams and the system operation is discussed together with an assessment of the reliability and measures taken for handling operating risks during floods for the dam, which has some stability concerns.
The disused Stapylton quarry is located in the suburbs of the Queensland Gold Coast. Gold Coast City Council, as part of the Northern Wastewater Strategy, has included the use of the quarry for storage and re-distribution of reclaimed water from the Beenleigh Water Reclamation Facility (WRF) to the downstream cane farmlands. A comprehensive EIS has been produced, which has strict water quality requirements for the quarry environs as well as the reservoir and outflow. This paper presents the background to the Northern Wastewater Strategy, the requirements for the Stapylton reservoir and the analysis performed for the detailed design of the embankment dam and the inlet bubble plume destratification system. The modelling of the destratification system was undertaken using the programme DYnamic REservoir Simulation Model (DYRESM) coupled with Computational Aquatic Ecosystems DYnamics Model (CAEDYM). The outcomes and implications of the modelling for the design and system operation including environmental monitoring are discussed.