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Russell Cuerel, Richard Priman, Michel Raymond, Ian Hanks
Following significant flood events across Queensland over the last five years causing significant damage in South East Queensland, Bundaberg Burnett region, St. George in the south west and more recently in Central Queensland in the Callide Valley, there has been renewed interest in finding solutions to flooding issues.Learn more
Increasing the available flood storage within a catchment is a well-known method of improving flood mitigation outcomes for developed areas. In many basins/catchments, potential flood storage development options (new storages or augmentations to existing storages) can be identified by reviewing previous water supply investigations and flood studies and by scanning topographic mapping. From such site identification there will often be numerous combinations of possible flood storage development options to consider because of the number of tributaries which may contribute to major flood events.
This paper outlines a methodology to screen, within a relatively short timeframe and at relatively low cost, a large number of identified flood storage development options and combination development scenarios and shortlist for more detailed analysis. The screening process is heavily reliant on hydrologic assessments to rapidly short-list scenarios for assessment and then relies on traditional engineering and economic assessments to do the fine tuning of the analysis.
Keywords: flooding, damages, impacts, flood storage, flood mitigation, dams, benefit-cost ratio.
Rob Ayre, Terry Malone
Abstract: Fairbairn Dam with a storage capacity of 1,301,100 ML is the second largest dam in Queensland in terms of water supply capacity. The dam forms the head works of the Nogoa – Mackenzie Water Supply Scheme operated by SunWater in Central Queensland. Completed in 1972, it consists of a zoned earth-fill embankment 49 m high and 823 m in length. The dam has an un-gated ogee spillway crest that is 4.2 m high and 165 m long, with an original design capacity of 15,600 m3/s.
In January 2008, Central Queensland experienced significant flood producing rains which were generated from low pressure systems associated with monsoonal activity across northern Australia. Rainfall totals over the 16,000 km2 catchment area of Fairbairn Dam varied in depth from around 200 mm to nearly 700 mm during a five day period to 20 January 2008. This resulted in the largest outflow from the dam since its construction and the first spill event from the dam since April 1990. While the dam had a significant mitigating impact, there was still major flooding of the township of Emerald, some 19 kilometres downstream.
This paper describes the performance of the dam during the event. Details of the data collected during and after the event, including assessments of spillway performance, dam safety surveillance and the implementation of the Emergency Action Plan will be presented. In particular, the paper focuses on the flood response concerning downstream communities and the resultant flood effects on Emerald and major infrastructure located in the downstream flood plain. It highlights the need for dam owners to have the capability of forecasting inflows and outflows to their structures and how this information contributes to the overall flood response system.
Keywords: dam safety, spillway, flooding, Fairbairn Dam, Emerald, SunWater, Queensland.Learn more