One of the longer beaches on the South Coast, Seven Mile runs for just over 7 miles (11.8 km) from Black Head down to the mouth of the Shoalhaven River at Shoalhaven Heads. The large Shoalhaven River has been supplying fine sand to build out this beach and its 1.5 km wide low barrier making it one of the younger beaches in the state. Because of the fine sand, particularly in the northern end, the beach has a wide low gradient. The northern headland houses the settlement of Gerroa, established in the 1920s. At the base of the headland Crooked Creek flows out over the beach, with a long foot bridge providing access from a car park and park to the northern end of the beach. South of the creek the road runs inland of the beach to Shoalhaven Heads. A caravan park backs the northern 1 km, then the Seven Mile Beach National Park runs for 7 km along the beach. The 729 ha park encompasses a beautiful littoral eucalyptus forest with a ground cover of bracken and Burrawang palms. Road access to the beach is provided in the north, and at the central Berry turnoff with an excellent park and shady picnic area behind the beach. Further along is a sandy track to the beach through the forest, with the southern access being at the Shoalhaven Heads Surf Club and car park, and from the river side car park.The long beach sweeps in a gentle arc, initially running west at Gerroa, then slowly turning to face the south east and then east at Shoalhaven Heads. Wave energy is lower in the north owing to protection by Black Head and its seaward reefs. Waves here average less than 1 m. By 1.5 km down the beach the waves have picked up to average 1.6 m and maintain this height to the river mouth. The fine sand results in a wide flat beach in the north with waves spilling over a wide shallow attached bar. However as soon as the waves pick up a second outer bar develops and runs the length of the beach. The inner bar is usually attached and cut by rips, every 300 m, following higher waves. Waves greater than 1 m begin to break on the outer bar, reform in the 50 m plus wide and deep longshore trough and often break heavily on the edge of the inner bar. At Shoalhaven Heads conditions are most hazardous when the river mouth is open, as strong river and tidal currents can sweep along the beach reinforcing the rips and trough currents.
Southport Beach (223) faces almost due west and receives low ocean swell as well as gulf wind waves. Waves average 0.5 to 1 m, and during higher wave conditions produce a double bar system, with 3 to 4 rips cutting across the inner and outer bars (Fig. 4.53). During normal low wave conditions the inner rips tend to infill and a continuous bar is attached to the beach. In addition the river flows across the southern end of the beach building out a large tidal and bar, cut by the deeper tidal channel.
The Scamander River flows though a meandering lagoon to the 500 m wide river mouth. While the river is usually blocked during floods and high flow the beach to either side can be washed away with strong tidal flows through the mouth. The river mouth shoals also produce some good surf breaks. Steels Beach (T 115) commences at the river mouth and trends due south for 4.9 km curving slightly to the southeast in lee of the boundary Henderson Point at Falmouth. The Scamander surf life saving club patrols the area south of the river mouth. The beach receives waves averaging up to 1.5 m which maintain a well developed rip-dominated 100 m wide surf zone, with up to 20 rips forming along the beach, and at times linking to form a continuous longshore trough. When Henderson Inlet is open strong tidal currents and a rip flow along the point. The beach is backed by a 50-100 m wide hummocky vegetated foredune, then a continuous 200 m wide wetland, which links with the lagoon in the south, the lagoon deflected 2.5 km south to the inlet. The only access is in the north from the southern section of Scamander, with a 200 m long walk across the wetland and dune to the northern tip of the beach. When the lagoon mouth is blocked the southern end of the beach can be accessed from Falmouth.