Sediment samples were taken along the open coast beaches during the April 2013 site visit, from the dune and swash zone of the beach, at sites shown in Figure 3-7. Sediment samples are analysed to determine the particle size distribution, which contributes to the erosion assessment by factoring in the ‘moveability’ of different grain-sized material.

Generally, sediment grain-sizes range from coarse to fine sands depending on the location within the study area (Table 3-4 and Figure 3-8). For the open coast, samples containing the most fines were taken from the dunes near the Ocean Grove Spit and Ocean Grove Main Beach. It is likely that some of the finer material at these locations has been sourced from the estuary. The coarsest samples are located near Point Lonsdale, Thirteenth Beach and Breamlea. These are the highest energy locations, and where there are eroding cliffs. The Ocean Grove Spit swash sample is also relatively coarse, possibly due to proximity to the bluff.

Figure 3-7     Sediment samples locations

Table 3-4      Sediment sampling

Figure 3-8     Open coast sediment grain sizes for dune and swash zones

Sediment analyses have been undertaken previously for areas within Port Phillip Bay. Generally, the grain size differs quite markedly from location to location as shown in Figure 3-9 and Table 3-5.

Figure 3-9     Sediment sample and profile locations and net sediment transport directions (Cardno, 2011c)

Table 3-5      Grain sizes (D 50 ) for Port Phillip Bay beaches (Cardno, 2011c) - location points on Figure 3-9.