WHY? Because of their misunderstanding of why former Queensland Premier Sir Joh Bjelkie Peterson built the Wivenhoe dam in response to the 1974 flood.
"The Wivenhoe was held to 190% of capacity because of the 'Anna Bligh syndrome'," Rob Williams says.
Here's the rationale...
- The flood in Brisbane was avoidable if the original operating systems of Somerset and Wivenhoe dams were used.
- When Sir Joh., started building Wivenhoe Dam in 1975 it was designed to be a flood mitigation dam, not a water storage dam as it used under the present operating regime as introduced by the Labor Party.
- As a result of the Labor mismanagement of Lake Wivenhoe, thousands of homes and businesses flooded.
- How the original operating system was to work as designed was: Somerset to be the water supply dam for Brisbane on the Brisbane river, Wivenhoe to be the FLOOD MITIGATION dam below Somerset on the Brisbane River.
- Wivenhoe was not supposed to fill more than about 40%.
- When Somerset was filled by a non flood event 20% of its volume was to be released and held at Wivenhoe for consumption in Brisbane.
- If a food event happened above Somerset (as it did), whilst that 20% at Somerset was filling, Wivenhoe would release the water that was released from Somerset at a rate that did not flood Brisbane.
- When Somerset overflowed, Wivenhoe would collect that water which could then be released at a rate that did not flood Brisbane.
- The filling of the 20% of Somerset by the flood means that Somerset held a volume of water of that flood event equivalent to the holding of 20% of the capacity of Somerset.
- Under the new operating regime were Wivenhoe was used as a WATER STORAGE dam both Somerset and Wivenhoe were 100% full before the flood event in the Brisbane River Valley.
- Wivenhoe filled to 190% of its capacity.
- If you do the maths under the operating regime as Joh had it designed, to prevent a flood in Brisbane, Somerset’s 20% flood mitigation capacity plus another 70% of the flood event to be held at Wivenhoe.
- As Wivenhoe would have been only 40% full when the flood event started.
- This meant that under the original operating regime as designed, Wivenhoe would have reached 110% full which is very manageable in its design.
- The flood waters held in Wivenhoe could then be released at a rate that did not flood Brisbane. As a flood mitigation dam, water would be released until it was once again 40% full.
- Releases from Wivenhoe would be timed so as to reach Brisbane as the tide is going out and to be a maximum just before low tide and as the tide comes in the flow to be reduced.
- A new water supply dam and a flood mitigation dam below it needs to be built on the Bramer River which would protect Ipswich from flooding but this won't happen as Labor and it's coalition partner, the Greens hate dams.
- During the Bjelkie Peterson era, 60 Dam sites were identified, 30 had the land mass acquired and owned by the Government.
- The Labor Party sold off 30 sites and built nothing!
- There have been no dams or flood mitigation construction since Joh left office!