Limitations of emergency action plans

Emergency action plans (EAP) might not always describe all possible dam hazards and/or emergency scenarios in complete detail. However, the actions for those described scenarios should be representative.

The effectiveness of emergency action plan provisions can be limited by a range of factors including:

  • the adequacy of available communications during an event
  • the accuracy of the available flood modelling and maps.

Communication limitations

The effectiveness of an EAP will often depend on the effectiveness of the emergency groups and other systems that are involved.

If these groups initiating warnings and notifications are impacted, they may need to seek alternative arrangements.

Flood modelling and map accuracy

EAP maps are indicative of the zones likely to be affected for the particular low-probability extreme events modelled. The map is not a guarantee that those zones will be affected nor that other nearby areas will not be affected.

Map users should be alert to the potential dangers in relying absolutely on possible inundation shown in mapping. These maps may suggest a precision that may not be justified in a real situation.

Inundation maps found in EAPs should only be considered indicative of what might occur during an emergency event.

EAP flood models are typically arranged by the dam owner and may have limited accuracy for real time flood events.

Explanatory notes

  • To be accurate, flood maps rely on the dam owner to undertake accurate modelling to determine inundation depths for a particular event and to make accurate assumptions about the particular dam failure scenarios. If a failure occurs, the actual scenario may prove different to that assumed for the mapped event.
  • Inundation map modelling may have been calibrated for historical events. Because such events are typically much smaller than extreme events that threaten dam integrity, the accuracy can diminish when extrapolated to larger events, and in urban areas a substantial number of additional dwellings can be inundated.
  • Inundation mapping is typically based on extreme theoretical storm event models that are centred over the dam, rather than actual storm events over the entire catchment. Inundations at particular locations downstream during actual events may be very different because the magnitude of other concurrent flooding may differ to that assumed in the original modelling.

Also consider...