Flood modelling of local catchment runoff was completed the Empire Bay catchment for a range of annual exceedance probabilities of storms from 100% AEP to 0.5% AEP and up to a PMF event.

In a 1% AEP event, the modelling shows that some properties and roads may be inundated up to 0.5m. This occurs notably around Gordon Road, Boongala Avenue, Rickard Road, and Greenfield Road in the main residential area of Empire Bay and around the main drainage channels at Pomona Road and Empire Bay Drive to Palmers Lane in the rural residential area. In the 1% AEP event, the modelling showed that 22 houses are flooded above the floor level when the storm runoff is combined with a 1% probability of exceedance level in the estuary.

Mapping of high provisional hazard in the catchment for the 1% AEP event shows that it is limited to the channel behind Myler Avenue and the channel north of Pomona Road which conveys runoff to Allawa Close. Scattered occurrences of high hazard also feature adjacent to parts of Empire Bay Drive. Hydraulic categorisation mapping for the 1% AEP shows floodway areas along the main watercourses from Pomona Road across Empire Bay Drive, and also some road near the main residential areas of Empire Bay and Bensville. Flood storage areas are identified in some properties, roads, and the open space / vegetated areas within the catchment. Increases to sea levels due to climate change have the potential to significantly affect flood impacts, particularly in the low elevation areas of the Empire Bay catchment. The Floodplain Management Authority’s Prioritisation Ranking table for the Empire Bay catchment is included as Appendix D.