This section of coast is subject to overtopping and inundation hazards. An assessment of the overtopping of the shore protection (seawall and revetments) was undertaken for Lonsdale Bight. This showed quite a significant hazard for the present day and in future with sea-level rise increases. The results are consistent with visual inspection of the area and information from the asset managers, the seawall is regularly repaired due to the effects of direct wave impact. Through time the incidence of damage due to wave impact is likely to increase, therefore continued maintenance and upkeep in this area is vital. The overtopping hazard decreases further around Lonsdale Bight due to the change from vertical seawall to revetment (which also increases in elevation from Lawrence Road) as well as a general decrease in wave energy with distance from the bay entrance.

Inundation is likely to be the overriding hazard for the Queenscliff area, more specifically, Fisherman’s Flats. The Fisherman’s Flats shoreline is significantly lower than the rest of the Queenscliff area; therefore any inundation is likely to originate from there. The shore protection is in very poor condition in some locations, and not forming a consistent barrier. The newly upgraded marina shoreline is approximately 0.5 to 1 m higher.

The lowest areas of Fisherman’s Flats already pool runoff in high rainfall events, thus the inclusion of saline inundation will increase the vulnerability, although similarly to the Barwon Estuary the likelihood of the two hazards occurring together is low. The stormwater pumping infrastructure has been upgraded recently to address the runoff issues. It is recommended that investigation into management options to mitigate the effects of saline inundation in this location should occur in the near future.

At the southern end of Swan Bay, an assessment of the inundation of Lakers Cutting and the Lonsdale Lakes development was undertaken. The inundation vulnerability also extends to the Bellarine Highway and properties in the vicinity of Murray Road. The extent of inundation of this area becomes significant under a 1% AEP event with 0.2 m SLR. In this event, a low section of the railway embankment overtops west of the Marine Discovery Centre, possibly impacting a small number of properties along Murray Road. The timing and depth of inundation for this area during this event is likely to be low; this should be considered in subsequent risk and mitigation studies. In a 1% AEP event with 0.5 m SLR, the flood extents increase significantly. It is recommended that the railway embankment is further investigated, particularly the permeability, as with minor adaptation (e.g. valving of culverts and removal of drainage channels) this could aid in inundation mitigation during lower events. Under higher sea-level rise events, the embankment would likely be overwashed. This will impact the Bellarine Highway.

For Swan Bay, the inundation hazards are less significant. There is little development around the bay, thus the key issues will likely be related to habitat resilience. The surrounding land areas rise gradually to higher land, therefore there appears to be nothing inhibiting any natural roll-back with sea-level rise.