WAS BRISBANE 2011 FLOOD NECESSARY?

byMartin Knox

Chemical Engineer, independentFebruary 5, 2012

Author: The Grass Is Always Browner, Speculative Fiction, Zeus 2011.

PURPOSE

• to investigate the hypothesis that the flood that peaked at a height of on January 2011 had been engineered for that effect despite less flooding being achievable.

METHOD

• Evidence of: 2011 flood effect at West End Ferry

• Evidence of: 2011 rainfall, dam releases, tides• History of flood heights at West End Ferry• Deduction of needed and actual dam releases

in 2011

GOING DOWNThe flood level peaked just below floor level.

HIGH WATER MARKThe 2011 flood peaked just below the 1974 flood level used for balcony top

FLOOD LEVEL FORECASTS AND RESULTSForecasting was blase’ then cautious, making extra work.

• Al'Cove 1974 mapped level was 5.76m• Initially, on Tuesday, there was no indication of height

and I assumed 1 metre or less in the garage.• Morning Weds, ABC AM 612 4QR 'more than 1974'

level.• Midday Weds, ABC AM 612 4QR 'at 1974' level.• Evening Weds '5.72m at reference position CBD.‘• Morning Thurs January 13th, flood had peaked at 0.20m

below balcony level, built at 1974 level 5.76m, therefore at 5.56m.

All garages were flooded to the ceilingContents were taken to the dump.

There were plenty of people helping to clean up.

RESULTS

• Flooding was controlled to meet the 1974 flood levels (using a model calibrated for this level).

• Or coincidence?

ANALYSISnotional physical model design

catchment

dam riverFlood plain

sea

rain

PRINCIPLESConservation of mass.Flow under gravity to sea level.Fluid hydrodynamics.Subdivision into analytical blocks.Iterative calculation between adjacent blocks to find effects of causes.

PROPERTIES

cyclone

ANALYSIS

1. Rainfall is unpredictable.2. SEQW sales recovering from severe drought.3. SEQW could profit from storing >100% capacity.4. Water users not deterred from wasteful use to profit

from sales.5. SEQW have no direct penalty from causing flooding.6. Flooded properties occupied by poor people, small

businesses and cheap commercial properties able to absorb losses.

Numerical model• CalibrationRainfall events of various sizes in various parts of the river

catchment require ongoing data.January 2011 events used to extend calibrated accuracy of

modelEffects of dam releases take several days to appear in

Brisbane. • Predictions Confident predictions of Brisbane effects cannot be made

with calibration by only two events (1974, 2011 data).

DISCUSSION

• Responsibility for flood damage• Insurance• Falsification of engineering reports• Financial motivation• Political responsibility

CONCLUSION

• the flood that peaked at a height of on January 2011 had been engineered for that effect despite less flooding being achievable.

RECOMMENDATIONS

• Independent scientific tribunals to be appointed by local authorities to plan water resources.

• Devolve all Queensland State Government powers to local governments and terminate by referendum.

• Flooding and water supply to be managed by separate scientific authorities.

APPENDIXMID FLOOD OBSERVATIONS Thursday 13th January 2011• It is 4am, said to be the time the flood will peak. I am at Dale's a few

streets away, anxiously awaiting enough light to go safely and survey the damage. I was devastated when it began to rain again but it soon stopped. I am hopeful of little damage upstairs but with the garage contents to be written-off. I am resigned to cleaning up, which will take many months, repairing and carrying on living there, always with the threat of further floods. I am feeling stupid about not realising the risk before and not at all when we purchased the place. I don't remember ever getting a building survey done. No wonder the place seemed cheap. I am also disappointed that the Wivenhoe flood mitigation scheme dumped water at the top of the flood. I think they were running overfull at about 130% illicitly. The purpose of Wivenhoe was so that 1974 conditions will not be repeated, but here we are....it looks like the scheme will have made precious little difference other than to concentrate the flood to a higher peak than would have occurred naturally. A dam is needed on the Bremer.