Geo100 Brisbane Floods

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  • Topic: Flood, Brisbane, Brisbane River
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  • Published : March 28, 2013
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ESSAY
As natural disasters are inevitable, it is essential that we as humans mitigate the potential outcomes caused by these disasters. This essay will explore the 2011 floods of Brisbane and whether proper planning and preparation could have minimised the outcome. It will further explore the impact the Wivenhoe Dam had on the floods and discuss whether dam maintenance; level supplies and warnings could have helped.

December 2010 and January 2011 saw Queensland experience record-breaking rainfall that has not been seen since 1960. Approximately 1 000 millimetres of rainfall was recorded in January alone, which caused the second biggest flood Brisbane has experienced since 1974 (Hornet & McAneney, 2011:1150). The 2011 floods caused severe devastation throughout Brisbane with over 26 000 people loosing their homes and over 5 000 businesses around the city either partially or completely flooded. It further caused around ninety kindergartens and sixty schools to be affected and unusable. However the greatest devastation was the loss of twenty-three people’s lives as a direct result of the floods (Calligeros, 2011:4).

The Queensland Government also suffered a major financial repercussion from the floods. Over 440 million dollars was spent in repairing roads, bridges, power poles and other public facilities that were destroyed (PM With Mark Colvin 2011). This kind of spending by the Government caused speculation that if proper planning and preparation been implemented, the Brisbane floods could have been mitigated. This speculation further lead to the investigating of whether the Wivenhoe Dam helped or hindered the floods.

The Wivenhoe Dam opened in 1985 after the great Brisbane floods of 1974 occurred and was seen as a solution to prevent further floods from happening again. All the dams, creeks and rivers surrounding the Wivenhoe Dam were connected that any potential overflow could run straight into the Wivenhoe and therefore have minimal risk of overflowing. However what occurred in 2011 was not what was planned when building Wivenhoe many years earlier. Wivenhoe Dam was built to hold a water supply of 1.15 million millilitres of water, with a capacity to hold 1.45 million millilitres at Full Supply Level or FSL. The 30 million-millilitre difference was allocated as a reserve for floodwaters to help mitigate flooding (Honert & McAneney, 2011:1152). Although a reserve level had been allocated in the dam, the issue was that there had been constant and heavy rainfall in the previous spring months. This led to the Wivenhoe catchments being relatively full prior to the downpour that occurred in the December 2010 and January 2011. This rain further caused the surrounding rivers and creeks to overflow causing minor river flooding, with water then starting to flow into Wivenhoe to help prevent major flooding.

Leading up to the floods Wivenhoe peaked at 1.50pm on Wednesday 12th of January reaching an astounding 2.29 million millilitres. (See Appendix 1 – Table 1.0). A day later Brisbane River peaked at 4.46 metres at 2.57am on Thursday 13th of January, causing major flooding to begin. (See Appendix 2 – Graph 2.0). It was during these two days that the role the SEQWater played was questioned, as they were aware that the dams were high enough to overflow. This speculation was further fuelled when it was made known that SEQWater only released 60% of the dam’s water, moments before the flood engulfed Brisbane (See Appendix 3 – Table 3.0).

SEQWater is the company in charge of the Wivenhoe and Somerset Dams and have three simple operating guidelines that they must follow (See Appendix 4 – Guidelines 4.0). It was apparent that none of the guidelines were followed for a number of reasons. Firstly this was evident as when the Wivenhoe and Somerset dams began filling up as a result of the severe wet weather, SEQWater did not release any water from either dam until Tuesday 11th of January. As they had left the water...
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