The purpose of this study was to assess the potential inundation hazards for the Bellarine Peninsula and Corio Bay, and provide information to aid land managers to understand the local processes and enable them to plan and formulate appropriate responses.

The study area consists of a variety of coastal environments. The Bass Strait open coast section of the study area is generally a high-energy environment with a relatively consistent wave climate, shallow nearshore bathymetries, consolidated dunes/cliffs and unconsolidated dunes, ranging in elevation from 2 to 30 m AHD. Headlands and rocky foreshores have fixed the ends of the local beaches, and characteristic arc and zeta-curve shaped beaches lie between the fixed points. Inland at Breamlea and Barwon Heads there are low-lying land areas vulnerable to inundation.

The entrance to Port Phillip Bay is a complex environment dominated by swells and strong currents. Within the bay the tidal range is lower than that in Bass Strait. The influence of swell decreases with distance from the bay entrance and the resulting environment is quite different. The wave climate is dictated by wind, meaning wave heights are fetch-limited. Due to sedimentation, water depths on the western side of the bay are shallow near the Great Sands, resulting in lower (depth-limited) wave heights.

In the vicinity of the entrance, the Lonsdale Bight coastline consists of high cliffs, long sections of seawall and revetment and dunes. The key hazards are overtopping of the protection structures and inundation of the low-lying areas around Queenscliff and Swan Bay. Further north along the St. Leonards and Portarlington coast the shoreline elevation is low, leaving some discrete areas vulnerable to inundation and erosion during storm events. The Clifton Springs coast from Portarlington to Geelong consists of cliffs with narrow beach widths at the base. The hazards here are mostly slope stability related, with some low-lying areas vulnerable to inundation. The coastal processes are dominated by wind, wind-waves and currents. The Corio Bay area is lower energy in comparison to the rest of the study area. Wave heights are more significant during north easterly wind events, due to the greater fetch from this sector; however the easterlies and nor’easters still produce waves that are able to have an effect on the shoreline. The northern Corio Bay area is also low energy, the energy increases slightly towards Point Wilson, due to the exposure to the wider bay. The shoreline is mostly rocky with low-lying hinterland behind.

A site visit and review of all relevant data sets and previous studies was undertaken early in the study. After consultation with the Project Control Group (PCG) and technical reviewers, the methodology was refined to ensure the most appropriate methods were undertaken to deliver the desired project outcomes. Due to differing landscapes and levels of hazard and potential risk, the appropriate scale and resolution of the modelling was determined for each study compartment.

The initial modelling considered waves and water levels throughout the study area, which enabled the determination of design conditions for subsequent inundation modelling. Inundation hazards were determined using hydrodynamic and static modelling (for less complex areas). Due to the nature of the differing coastal environments there were some limitations within the inundation assessments of this study, and these were considered and reported on within the findings.