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Trevor Daniell, David Kemp and Jenny Dickins
Early February 1997 saw the occurrence of heavy rainfalls over a wide area of South Australia’s north. One of the worst hit areas was near Olary, in eastern South Australia, where over a three day period, rainfall totals up to 320 mm were recorded. Within this period, localised, short duration intense rain occurred. In one four hour period on 7 February, about 200 mm fell.
The rain produced floods that washed away large sections of the main Sydney to Perth railway and inundated long sections of the Barrier Highway. Repair costs were of the order of $6 m for the railway and $1.5m for the road. Damage to rural infrastructure in the region was substantial. Flows within the catchment would have been sufficient to wash away most stream gauging stations.
The airmass over much of South Australia was of tropical origin, contained a high amount of moisture and was unstable. Thunderstorms were the main rain producer, consequently the event was characterised by localised, very intense rain episodes. This contrasts with the March 1989 floods, where it rained at a fairly steady rate over large areas for durations up to 24 hours, as a monsoon low tracked across the state.
Analysis of the depth-area relationship for the Olary storm indicates that the relationship to be used for design purposes should be the humid area relationship of Australian Rainfall and Runoff, not the arid area. This is reinforced when it is considered that the 1997 rainfall was localised, not general rain as in 1989.
Investigation of the event indicates that the Olary Creek catchment experienced overland flow, resulting in much higher peak flows than would occur with more frequently occurring “normal” processes. It is possible that any catchment may change its behaviour with extreme rainfall, and produce flows well in excess of those predicted with currently available runoff routing models, or flood frequency analysis of “normal” events.
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1998 Papers
1998 – The Olary Floods February 1997 Implications for South Australia
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Trevor Daniell, David Kemp and Jenny Dickins
Early February 1997 saw the occurrence of heavy rainfalls over a wide area of South Australia’s north. One of the worst hit areas was near Olary, in eastern South Australia, where over a three day period, rainfall totals up to 320 mm were recorded. Within this period, localised, short duration intense rain occurred. In one four hour period on 7 February, about 200 mm fell.
The rain produced floods that washed away large sections of the main Sydney to Perth railway and inundated long sections of the Barrier Highway. Repair costs were of the order of $6 m for the railway and $1.5m for the road. Damage to rural infrastructure in the region was substantial. Flows within the catchment would have been sufficient to wash away most stream gauging stations.
The airmass over much of South Australia was of tropical origin, contained a high amount of moisture and was unstable. Thunderstorms were the main rain producer, consequently the event was characterised by localised, very intense rain episodes. This contrasts with the March 1989 floods, where it rained at a fairly steady rate over large areas for durations up to 24 hours, as a monsoon low tracked across the state.
Analysis of the depth-area relationship for the Olary storm indicates that the relationship to be used for design purposes should be the humid area relationship of Australian Rainfall and Runoff, not the arid area. This is reinforced when it is considered that the 1997 rainfall was localised, not general rain as in 1989.
Investigation of the event indicates that the Olary Creek catchment experienced overland flow, resulting in much higher peak flows than would occur with more frequently occurring “normal” processes. It is possible that any catchment may change its behaviour with extreme rainfall, and produce flows well in excess of those predicted with currently available runoff routing models, or flood frequency analysis of “normal” events.
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2006 Papers
2006 – Large Dam Instrumentation and Deformation Surveys in South Australia
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Lawrie Schmitt and Angus Paton
As the owner of most of the large dams in South Australia the South Australian Water Corporation (SA Water) is responsible for the safety of these structures and their designed function of water supply and flood control. In order to meet these responsibilities SA Water monitors the performance of the structures using engineering deformation surveys and various forms of instrumentation. This paper outlines the instrumentation and survey monitoring undertaken at SA Water large dams and discusses the issues arising.
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