This section of coast is managed by the Barwon Coast Committee of Management and is a 6.5 km section of beach from Blue Rocks to Barwon Heads (Figure 6-5). West of Blue Rocks, Barwon Water manages the foreshore directly fronting the water treatment facility (between BHCoM and CoGG managed sections).

Thirteenth Beach is backed by high dunes/cliffs with steep, almost vertical, scarps at the central and eastern ends of the beach. The nature of the dune/cliff features is not clear due to the unknown level of cementation or calcarenite in these features. The elevation of the dunes/cliffs ranges from approximately 5 m at the western end, to almost 30 m at the eastern end. There are exposed sections of calcarenite within the dune that appear to have fixed the shoreline position to some extent. Beneath the eroding calcarenite cliffs, scree has accumulated providing some natural protection to the base of the cliffs in this area. Shoreward of the calcarenite sections, some rocky reefs exist which are acting to reduce the wave energy in the nearshore zone. The shoreline is almost perpendicular to the dominant wave direction and this one of the most high energy areas in the study area. The beach width is relatively uniform, with only slightly narrower sections where the cliffed areas are fixed in place. This would indicate that the flux of sediment passing along the beach is relatively constant. The dominant sediment transport is west to east, and waves push sediment around Barwon Heads, where it is either deposited on and around the Barwon River ebb delta, or bypasses towards the Ocean Grove spit and Ocean Grove Main Beach. Some sediment is also likely to be imported into the estuary on incoming tides.

Behind the beach is Murtnaghurt Lagoon, a naturally segmented basin formerly connected to the Barwon River channel through a relict channel that is now disrupted by Plummer’s Bank. This is a 4 m high levee constructed in the 1950s to protect against ‘back door’ flooding of the Barwon Heads township (Rosengren, 2009). The likelihood of the dune/cliff breaching and flooding the low-lying hinterland and the lagoon is very low due to the elevation and volume of the dunes/cliffs.

No inundation maps were produced for this area, as there is no inundation hazard risk to the hinterland from the coast. Possible flooding of this area and Murtnaghurt Lagoon is discussed in the Barwon Heads and Lake Connewarre model section.

Figure 6-5     Compartment 2: Blue Rocks to Barwon Estuary