Author : J. V. Hodgkinson F. C. A. Chartered
Accountant : Aug 2006 to November 2013
The principal thrust of this
This is my review based on official
statistics and documents. It is done in conjunction with Ron McMah, grazier
of Imbil and Trevor Herse, retired of the Gold Coast
Flood Inquiry Final Report 15/03/12: The Flood
Inquiry did not review my 120 page submission related to this website
information. Their Terms Of Reference "did not permit examination of
topics such as changes to Infrastructure whether by way of new dams or upgrades
to existing dams" Page 438. This was a short term view
restricting the Inquiry by the Government (Bligh) that
merely left the Inquiry to clean up the mess of the 2011 flood in Brisbane and
Ipswich without the
benefit of showing how to avoid it altogether.
Flood Inquiry 25th
The minor flood has a clear demarcation of 34 hours for the period 3pm on Friday the 7th to 1 am on Sunday the 9th of January 2011. In that period the Engineers' log shows only 11mm of rain in the Wivenhoe catchment and 23mm in the Somerset catchment. However these figures do not seem to fully match the rainfall stations. Comparison is difficult as rainfall every hour is required in the matching process. View rainfall stations
The rainfall station information was used to examine the veracity of the Seqwater claim that the 2011 flood was 190 per cent greater than 1974. Even with the minor flood added in to the 2011 flood and the weeks of draining afterwards also claimed, the percentage quoted is fanciful.
Seqwater claim that it was the spread of rainfall that made the difference is also under severe pressure as a credible statement. Excluding the minor flood, of the 11 rainfall stations in the Wivenhoe catchments in 1974 only 3 were marginally less than 2011. Of the 5 rainfall stations in the Somerset catchments, all registered more rainfall than 2011. Both floods were on saturated catchments which means conversion to inflow conditions were similar.
How the minor flood was dealt with is becoming clear as the evidence and cross examination progresses.
Depending on the evidence, this Seqwater graph may change but not sufficient to alter one's overall view of the problem.
Notes on Interim report of the Flood Inquiry (2nd August 2011)
As expected, this interim report deals with the aftermath of this 2011 flood. It was designed to observe and recommend changes necessary to deal with the next "wet season". It does not review the 120 page submission made that relates to this website for permanent relief from floods and droughts.
However, I will be raising three interrelated matters that I have observed (Confirmed by letter to the Flood Commission 5th August 2011). They are
Deputy Premier Bligh and Minister
Hinchcliffe were alerted to this possibly that with full dams, a major
situation could arise with heavy rainfall. Click
End of notes on interim flood Inquiry report
Additional observation to Flood Inquiry notes (my observations 24/05/2011)
* It is generally accepted in evidence that the water above the Wivenhoe/Somerset dams represents 50% of the water that reaches the Brisbane River mouth.
This sweeping statement does not stand up to close scrutiny and, as a consequence, wrong decisions are drawn. In this 2011 flood, using Seqwater information, the above dam Wivenhoe/Somerset catchments recorded flows of 2,650,000ML. Modelled flows accepted by the Flood Inquiry in evidence had the Lockyer Creek flow at 701,858ML and the Bremer River flow at 426,541ML. I have estimated the Mid and Lower Brisbane River and Oxley creek on the basis of catchment areas and rainfall to be approximately 426,541ML. The "below dam" flows total 1,591,043ML. Click to expand graph
The "above dam" contribution was therefore 62.5 percent of the total flood. That means that the "above dams" water contribution was 60.0 percent more than the "below dams" contribution.
Apart from putting true meaning into "drought proofing SEQ" the principal objective of this website is to contain the flow of the Wivenhoe/Somerset until after the flood peak has passed thereby eliminating the "above dam" water from the flood.
The releases from the Wivenhoe combining with the "below dam" flows of the Bremer River and Lockyer Creek are shown on this graph. It reveals that, with the Wivenhoe/Somerset contained until after the flood, the velocity and volume of the flood would have been halved. The top half does the damage.
Official confirmation of the resulting percentages above the dams of all floods follows-
* The Principal Hydrologist Water Planning Sciences DERM confirmed to me in writing on the 3rd March 2010 that the percentage is 56.5 percent above the dam and 43.5 percent below the dam. This means that the water above dam provides 29.8 percent more water than water below the dam.
Downstream of Mt Crosby the percentage of 56.5 rises to 58.0 percent.
This "above dams water " percentage is calculated by their IQQM computer model which has the force of Law. For this calculation it calculates all the flows in the Brisbane River and its tributaries that have occurred in the period 1889 to 2000. It includes all floods without exception. The flows are pre-development flows (No dams, no people).
Evidence at the Inquiry confirms that there is no official modelling. Therefore this calculation is the only authoritative percentage calculation. It should be kept in mind when viewing sweeping statements on the influence of the Bremer River and Lockyer Creek on Brisbane.
Water below the dam is principally from the Bremer River, Lockyer Creek and other creeks that enter the main Brisbane River. The hydrologists seem to agree that very large enforced releases from the Wivehoe dam (no space left in flood compartments) acted as normal in creating a barrier to these tributaries.
in addition it forced water back up these tributaries in this 2011 flood. In the Bremer River it raised the level at One Mile Bridge by 7 metres according to the hydrologists. That bridge is 47klm from the Bremer River mouth.
The flood waters combined at speed and descended on Brisbane. Approximately 50% of the water above the dams was "mitigated" (held back) by the Dams' flood compartments.
* The requirement that the ecology must receive 66% of all water that passes through the dams has not been mentioned. Also not mentioned is that, due to a drafting error, this percentage has been raised to 78% costing us 160,000ML annually, seems to have escaped attention. This error will cost us the price of three desalination plants plus ongoing costs and interfere with our water security.
* Our main water supply being "low pressure systems" or "Uncommon events" as described by Mr Drury of SEQWater have not been recognized in the Inquiry. As we have seen they have the ability to fill our dams from 20% to 300% of capacity. They account for 90% of our water and a large number did not adhere to the now recognized "wet season" December to March. They can come at any time.
* Permanent reduction of the FSL (water held for us and the Ecology) by 25% will most likely bring on recycled water and require the proposed desalination plants earlier than planned.
* There is heavy concentration on Dam and Flood management. This is the main objective of the Inquiry.
* Solutions may occupy the second half of the Inquiry. With over 600 submissions, absorption of them will be a major undertaking for the Inquiry. Revision 27th May 2011. An extension of the Inquiry to the 24th February 2012 has been announced.
Flood Inquiry submission
A submission has been made to the Flood Inquiry. It encompasses 120 pages and three additional addendums. Its direction is the permanent solution to damaging flooding and extended drought conditions in SEQ.
The provision of water in South East Queensland is a complex issue. There is ample evidence that it is not fully understood since the instillation of the Wivenhoe Dam. Reading of the evidence of the Flood Inquiry reveals that it continues.
There seems to be no understanding that our main water supply is random "low pressure systems" which, apart from filling our dams, creates extremes of flood and the appearance of "drought". Their control through further storage is essential.
While the new Seqwater dam level site is very good, it does not start early enough (1996), nor is the gradient high enough, to view these "low pressure systems" in operation. SEQWater's previous graph from year 1990, and accompanying this sentence, shows their operations and confirms that Summer "wet season" rainfall has been inadequate since 1992. We rely almost entirely on "low pressure systems" which pay little heed to the time of year.
The submission therefore deals with the root cause and its solution in what we have seen in the last 10 years, the shrinking of of our water supply to 18% of capacity and the recent overflows of 285% of capacity. Both had, and are having, a traumatic effect on our citizens.
A brief outline of the 2011 flood. In my view, the 2011 flood was similar
to the "little referred to" second major flood in
February 1893 which concatenated (piggy-backed) on the back of a minor
flood. It came to within 0.28 metres of topping the first flood in 1893.
The three major Hydrology firms engaged by the Insurance Council of Australia in their study of Ipswich seemed to agree. They ignored the minor flood altogether.