Uncommon events

Author : J. V. Hodgkinson F. C. A. Chartered Accountant : Aug 2006 to November 2013    

The principal thrust of this website is
FLOOD PROOFING BRISBANE from damaging floods to the point of extinction. MITIGATING flooding in Ipswich and Gympie. Putting REAL MEANING into "Drought proofing SEQ" and ensuring our water supplies by natural means well into the future

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




Update on October 2010 rainfall event (5th October 2010) At bottom of this page

Update on late February/early March rainfall and inflow (8th March 2010)

The Late February/Early March rainfall of 2010 saw our dams increase from 69% to 97% as Flooding Rain 08 03 2010.jpg (61098 bytes) at the 13th March 2010. A click on this photo will give one a comparison of the rainfall at flood time for all large events in the short life of the Wivenhoe since its commissioning in 1986. Five rainfall stations that were in existence for the whole of the period were used for consistency.
Photo : Rainfall comparison


The Department of Environment and resource Management (DERM) have been good enough to provide me with the inflows that would have occurred if the dams and other Inflows1988 to 08032010.jpg (61098 bytes) infrastructure were not present. This provides us with sufficient information to judge the inflow from the recent February/March 2010 event which inundated Western Queensland. Our catchments benefitted from the same weather system. Comparison is made with all major events in the short life of the Wivenhoe.
Photo : Inflow comparisons

Wivenhoe Uncommon to 2009.jpg (86136 bytes)All of these events overflowed the dams with the exception of 1996. 

With no large events to fill our dams from 2001 to 2007, four near-misses rescued us from 2007 to 2009 the largest being May 2009 which failed to come west enough to cover the Wivenhoe catchment. Cyclone Hamish missed us altogether.
Photo : Wivenhoe dam level graph

These large scale events are random with an an average of 3.7 years from 1841. Most Low pressure systems 1841.jpg (116692 bytes)occur below 3.7 years and as a consequence, a small number exceed this average by a wide margin. Their absence was misread as a drought. There was no provision for their extended absence although it was evident in the dam level graph, even to the unpractised eye, that eventually extreme difficulty would be experienced  in a protracted absence.

Photo : Frequency of "uncommon events".

The evidence is now conclusive that Large Scale Events are our main water supply. We have all just witnessed a 30% fill from the recent event. While it was a major event out west it was a comparatively minor event in our catchments as evidenced by the rainfall comparison. The short history of the Wivenhoe shows us that 5 out of 6 overflowed the dam. Our dams are too small to accommodate these inflows and control our water supply for the benefit of our ecology and residents of South East Qld. We have the solution and it follows below.

October 2010 "uncommon event"

This 5 day event was unusual in that it did not have a low pressure system to support it. Never-the-less it provided sufficient rainfall to overflow our rivers and creeks causing some residents harm.

The release of water from all dams was spectacular.

Alert to Minister Hinchcliffe

The following is an extract from my letter to Hon. Mr S. Hinchliffe, the then Minister for Infrastructure and Planning, sent on the 23rd April 2009 three weeks before the May 2009 "uncommon event" mentioned above.  The alert to the Minister followed a meeting with him in January 2009. The meeting had the support of the senior policy advisor to the PM (Kevin Rudd).

"The way I see it, the difficulty for you and all who support the Traveston is that on the mathematical certainty of the return of the “uncommon events” the dams will overflow. That by itself should have people in SEQ questioning if those in charge understand what they are doing. Historically there has been 11 “uncommon events” within 1 year of each other (April 1988 & April 1989 for example) and there will be a tremendous loss of water over spillways with full dams. In my view justification of the Traveston will be under severe stress and storage in the Borumba Dam together with its additional yield, vindicated."  

The Traveston battle was lost by the Government but the use of the Borumba Dam expanded to 2,000,000ML for storage, or almost twice the size of the Wivenhoe, is still valid. It will eliminate the need for 3 more desalination plants of the Tugun Plant size.

Further reading Borumba Dam Proposal and Borumba Dam Appendix