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What is the Flood Adjustment Model?

The Settlement Agreement provides compensation to Claimants where the flood damage was caused by the operation of the Wivenhoe and Somerset Dams. As it’s possible that some damage would have occurred to your property in the flood, regardless of how the dams were operated, assessors need to be able to establish how much damage was caused by just the operation of the dams.

To do this, the Court has approved a Flood Adjustment Model. This modelling has been established by an expert who determined both the actual flood level, and the ‘counterfactual’ flood level that would have occurred if the dams were operated differently.

In short, the Flood Adjustment Model gives assessors a way to determine how much of the damage caused to your property is ‘compensable’ under the Settlement Scheme.

What is the flood adjustment factor?

The model shows assessors the flooding that actually happened and the flooding that would have happened if the dams were operated differently. Using this, assessors are then able to measure the difference between the damage that occurred and the lesser damage that would have likely occurred if the dams were operated differently.

Assessors measure this damage by using the Flood Adjustment Factor. The factor is a calculation based on these two flood levels, the information you have provided about your property type and the elevation of the property (how far off the ground the floor is).

Under the Settlement Scheme, losses must be adjusted by this factor to ensure compensation is only being claimed for the damage caused by operation of the dams.


How does the flood adjustment factor work?

The flood adjustment factor is calculated between 0 and 1. A factor of 1 means that all flood damage was due to the operation of the dams and the losses assessed will not be reduced. A factor of 0 means all of the flood damage would have occurred even if the dams were operated differently and the losses assessed will be reduced to zero.

If the flood adjustment factor is somewhere between 0 and 1, the losses will be reduced to take into account that some of the flood damage would have occurred even if the dams were operated differently. 


How is the flood adjustment factor calculated?

The flood adjustment factor is calculated by following these steps:

  1. Using the coordinates of the loss location and the flood adjustment models, the actual flood depth and the counterfactual flood depth above ground is generated.
  2. The counterfactual flood depth and the actual flood depth above the first floor* is then calculated by subtracting the elevation height (how far the first floor is from the flood depth).
  3. Using these figures, and the applicable damage indices, the following formula is used to work out the flood adjustment factor:

1 – (Damage Index at counterfactual flood depth above first floor)
Divided by 
(Damage Index at actual flood depth above first floor)

[The applicable damage index will be selected based on the information you provided about the building type.
View the ‘Damage Index Table’ for how the index is calculated.]

4. Your 'adjusted loss**' will then be calculated by multiplying your assessed losses by the flood adjustment factor.


How is the flood adjustment factor calculated for commercial properties?

For commercial properties, if there is no modelled counterfactual flooding at the location of the main building, the flood adjustment factor will be 1. If the counterfactual flood depth above the first-floor level is 4m or greater, the flood adjustment factor will be 0.

If the counterfactual flood depth is greater than zero, but less than 4m, the flood adjustment factor will be calculated using the above formula.

Example: Large factory

If the property was a factory that had a building area of 700 square metres, an actual above ground flood depth of 3m, a counterfactual flood depth of 0.75m, and assessed losses of $300,000, the following calculations would be used to determine the flood adjustment factor and the 'adjusted loss’:

  • The first-floor elevation is assumed to be 0cm due to the property type being a factory.
  • As the building area is greater than 650 square metres, it is deemed to be a ‘large business’.
  • The counterfactual flood depth above first floor would be 0.75m and the corresponding damage index for a large business would be 0.198440967
  • The actual flood depth above first floor would be 3m, and the corresponding damage index for a large business would be 0.931255
  • The Flood adjustment factor would then be calculated as follows: 1 – (0.198440967)/(0.931255) = 0.7869101696098276
  • The 'adjusted loss' will be calculated as follows: $300,000 (i.e. assessed losses) x 0.7869101696098276 (i.e. the Flood adjustment Factor) = $236,073.05.

How is the flood adjustment factor calculated for residential properties?

For residential properties, the flood adjustment factor will be 0 if the following circumstances apply:

  • For single storey houses and units, the counterfactual flood depth above floor level is 2.7m or greater;
  • For double storey houses and units, the counterfactual flood depth above first floor level is 6m or greater;
  • For high set houses, the counterfactual flood depth above the habitable floor level is 2.7m or greater.


If the counterfactual flood depth is greater than zero, but less than the flood depth outlined above, the flood adjustment factor will be calculated using the above formula.

Example: Single storey residence

If the property was a single storey residence, with a first-floor elevation of 0.5m, an actual above ground flood depth of 3m, a counterfactual flood depth of 1m, and assessed losses of $100,000, the following calculations would be used to determine the flood adjustment factor and the 'adjusted loss':

  • The counterfactual flood depth above first floor would be 0.5m (1m – 0.5m = 0.5m), and the corresponding damage index would be 0.677681
  • The actual flood depth above first floor would be 2.5m (3m – 0.5m = 2.5m), and the corresponding damage index would be 0.98152
  • The Flood adjustment factor would then be calculated as follows: 1 – (0.677681)/(0.98152) = 0.3095596625641862
  • The ‘adjusted loss’ will be calculated as follows: $100,000 (i.e. assessed losses) x 0.3095596625641862 (i.e. the Flood adjustment Factor) = $30,955.97.

How is the flood adjustment factor calculated for other types of properties?

Agricultural damages
If agricultural property has been flooded, the flood adjustment factor will be calculated by dividing the area free of counterfactual flooding by the total agricultural area (unless it is more appropriate to use a different methodology).

Pontoons and jetties
Claims for damage to only pontoons and jetties, where no damage to other structures is claimed, will not be adjusted for counterfactual flooding beyond the assessment methodology in the court-approved Settlement Scheme.

Subterranean inundation, inundation through drainage channels, infrastructure over a river or other miscellaneous property types
If the claim relates to subterranean inundation (e.g. underground car parks), inundation through drainage channels, infrastructure over a river (e.g. a bridge) or other miscellaneous property types, the actual and counterfactual flood levels may be determined from other evidence and/or expert advice.


What is my right to review?

You have the right to request a review of your flood adjustment factor and the inputs used on your claim within 28 days of receiving it.

Please note that the method for calculating the adjustment factor has been approved by the Court and you may only seek a review for the following reasons:

  • Incorrect representative coordinates were used;
  • An incorrect property or business type has been assumed;
  • An incorrect first floor elevation has been assumed;
  • Incorrect representative curves were used; and/or
  • An exception to using the Flood Model depths applies. In situations where assessors consider that the modelled flood depths may not accurately reflect the flood levels of the property, assessors may determine the actual and counterfactual flood levels from other evidence and/or expert advice and notify you of the methodology used.


You will need to include the perceived error in your request to review. It will be your responsibility to supply adequate evidence to show that the figures used to determine the flood adjustment factor were incorrect and you will be required to supply the correct parameters.

*‘Flood depth above first floor’ means the flood depth above ground minus the height of the elevation of the first floor. ‘First floor’ means the lowest habitable floor level of the property. The first-floor elevation will be determined by assessors and will be based on information which you have provided. Assessors may also have regard to additional information such as real estate data, floor level data accompanying the SFMP Report, documents or instructions provided by Claimants to establish loss, Google street view, or other available imagery.

** The ‘adjusted loss’ reflects the value of the losses sustained and is not the amount of money that Claimants can expect to recover. The value of the ‘adjusted loss’ will be reduced to reflect, among other things, the proportion of losses covered by the Sunwater and State of Queensland settlement, the shared legal costs incurred in administering the settlement and Omni Bridgeway’s funding commission.

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