After having to rebuild infrastructure again, and again, after big floods the Queensland State Government is now considering preventative measures.
Premier Campbell Newman has pledged to flood-proof parts of disaster-prone Queensland, by shifting suburbs to higher ground, raising highways, and building new levee banks.
Before taking this action further careful planning should be taken. While all these ideas have merit there are others that also should be seriously considered.
Furthermore, building new levee banks is not a good solution for many areas. It is disastrous when levee banks are broken or over-topped. The height has to be just right and who knows how high the next flood will be. Floods of 1893, 1841 and perhaps 1824 were higher than that in 2011. Furthermore, with global warming we can expect even bigger and more frequent floods than those.
Levee banks are probably unsuitable for the Brisbane River flood plain although they may possibly be useful in the Toowoomba region where conditions are different. Levee banks have failed in areas like New Orleans in USA, Northern Japan where they failed to stop the 2011 tsunami, and in China where hundreds of thousands of people have lost their lives when levee banks failed in the past.
More attention should have been made to flood-proofing after the 2011 floods. Instead much of the attention went on management and legalistic blame-finding in the control of Wivenhoe Dam. 753 submissions were made to the Flood Commission about what to do and very few of these have been followed up. There were several suggestions of merit that were totally overlooked. The least the Commission could do was to check out the merit of these concerning issues such as relief to Wivenhoe Dam (other than water level control), relief to the Brisbane River below the dam, and relief to the rainfall situation.
Relief to Wivenhoe dam can be effected by diversion of water below Somerset Dam to North Pine River. Another way is to divert water from Billies Crossing to North Pine River. Both of these involve tunnels. Further relief could be gained by extending Atkinson Dam to take overflow from Wivenhoe via a channel.
Diversion of water from below Somerset Dam to North Pine River
Reedy Ceek is just below Somerset Dam and extends east into Byron Creek. The D'Aguilar Range separates Reedy Creek from North Pine River. It is proposed to join Reedy Creek to North Pine River with a tunnel through the range terminating at a point near where Laceys Creek joins North Pine River. This gives a fall of about 10m over a distance of about 19 km which is enough slope for the water to run down. To get a greater head of water the tunnel could go about 3km further to a point below Lake Somerset dam. This greater head of water could allow for a shorter tunnel.
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The positive aspect of this is that a considerable amount of water can be diverted from entering Wivenhoe Dam.
Negative aspects are that the tunnel is long and therefore costly, and that the water will be diverted into Lake Samsonvale and North Pine Dam. The North Pine waterway out through Petrie will need to be able to take a larger flow, and may need some modification.
Diversion of water from the Billies Crossing area to North Pine River
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Lloyd Hamilton is a retired associate professor in geology from QUT.
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