Riverine flood inundation has been investigated in the past, however focused solely on riverine inundation. This assessment considered the saline inundation primarily, and coincidence of this with riverine events. An assessment of the coincidence of these two factors was undertaken, it was found that storm-tide inundation and peak riverine flows due to high rainfall do not occur at the same time. The assessment therefore included two higher frequency flood events, an annual peak flow and a 10% AEP flood event, with the less frequent 1% AEP coastal event.

The saline inundation potential for Barwon Heads is less significant than previously assessed (Future Coast, 2011). In a 1% AEP event with a catchment baseflow the low-lying areas of the estuary shoreline are inundated. These are mostly areas of habitat. In events with sea-level rise above 0.2 m, the flood extents become more significant. In a 1% AEP event with a 10% AEP catchment flow for the present day (i.e. 0.0 m SLR) the flood extent is greater than the equivalent baseflow case. The inundation is likely to impact the eastern bank of the river, at Ocean Grove, where the low shore protection is likely to be overwashed. Note, the shore protection here is not forming a consistent barrier and appears to have been designed to minimise shoreline movement on the river bend, rather than flood protection. On the western bank of the river (Barwon Heads) the inundation potential increases with increases in sea-level rise.