Flood Risk Overlay 2026

This flood risk awareness mapping has been prepared using the results of a citywide, fit for purpose flood risk assessment, using the most up-to-date rainfall information, new flood modelling software and industry best practice methodologies. 

 
The flood risk awareness mapping is a product to create flood risk awareness.  The flood risk awareness map:
is non-statutory and does not impose regulatory controls;
is based upon the combined effect of flood hazards and their likelihood, for all flood events up to and including the extreme flood event (probable maximum flood);
has been developed using latest flood models; 
includes parts of the City that have been mapped for the first time;
indicates degrees of risk, using the risk-based approach, through the following applied flood risk categories :
Very high risk - Unsafe for people and vehicles, and buildings are subject to structural failure in frequent floods. Flood events are both frequent and usually of the highest hazard
High risk - Unsafe for people and vehicles, and buildings are subject to failure in frequent flood events. Flood events are both relatively frequent and usually of high hazard.
Medium risk - Unsafe for people and vehicles, and buildings are subject structural failure in rare flood events. Flood events can either be rare with high hazard or relatively frequent with lower hazard.
Low risk - Relatively lower hazards in frequent to infrequent flood events. High hazards can only occur in rare and very rare flood events, when it is unsafe for people and vehicles and buildings can be subject to structural failure.
Maximum regional flood extent - Only floods in very rare to extreme flood events. Extent of the floodplain associated with very rare events and can include hazard of any type (low or high).
 
Flood risk is calculated using likelihood (AEP) and hazards (flood depth and flood velocity). Those areas within categories ‘Low’ through ‘Very high’ have been determined taking into account the geographic extent of flood depth and flood velocity (i.e. flood hazard classification using the Australian Institute for Disaster Resilience (AIDR) method) across the city for the statistical rainfall events identified below, combined with the likelihood of those events occurring (e.g. rare, infrequent, frequent etc.). The areas identified as 'Maximum regional flood extent' indicate the outer extent of the floodplain. In simple terms, this risk mapping represents the city-wide product of flood hazard and likelihood using a Risk Management approach for a present-day scenario.

 
The statistical design rainfall ‘events’ used in the flood modelling that underpinned the preparation of this risk map are:
20% AEP (generally known as 1 in 5 or frequent flood event)
5% AEP (generally known as 1 in 20 or infrequent flood event)
1% AEP (generally known as 1 in 100 or infrequent flood event)
0.5% AEP (generally known as 1 in 200 or rare flood event)
0.2% AEP (generally known as 1 in 500 or rare flood event)
0.05% AEP (generally known as 1 in 2000 or extremely rare flood event)
Extreme flood event

Tags: 2026, City of Gold coast, CoGC Open data, Flood, Flood Risk, Flooding, Open Data
Organization: City of Gold Coast