THE LADDERS OUTFALL

Click the photograph for a enlarged view

Physical Environment

Landscape  

“The Ladders” headland consists of Wagonga formation bedrock, which is made up of chert, conglomerate, agglomerate, slate, sandstone and phyllite (Ulladulla Geological Series Sheet S1 56-13). The shoreline within the general area is comprised of low cliffs, wave cut tidal rock platforms and sandy coves and beaches. To the south is Smuggler Cove and to the north is “The Ladders”, an unnamed beach, a rocky headland and then Wimbie Beach.

Bathymetry & Substrate

The outfall is located in a ‘shadow’ zone behind ‘The Ladders’. The seabed in the vicinity of the outfall comprises areas of rocky bottom and patches of sand. In some areas the sand cover above underlying rock is relatively thin and these areas are expected to vary in the constancy of sand cover in response to wave conditions. From the end of the outfall pipe a rocky bottom extends to the east for approximately 80 m where it falls away onto a sandy bottom approximately 7 m in depth. Shallow rocky reefs run parallel with the beach (Smugglers Cove) in front of the outfall pipe, each reef separated by gutters of variable depth. These reefs and gutters merge into the tidal rocky platform to the south and generally open out at the northern end into a channel that runs along the southern side of the northern headland. There is a rocky outcrop less than 2 m to the east of the pipe, which rises to 0.8m and restricts the movement of the effluent into deeper water.

Currents, Winds and Waves

The effluent generally moves very slowly from the rocky outcrop (see above) until it joins the mainstream flowing past the end of the headland. Measured currents in the vicinity of the outfall ranged from 0.04 m/s to 0.11 m/s. Three main patterns of oceanic movements in the vicinity of the outfall were identified (Sinclair Knight & Partners 1987):

• straight out to sea;

• around the headland immediately to the north and then heading north parallel to the beach; and

• southwards parallel to the beach, landing onshore south of the outfall.

At 0900 hours nearly 60% of wind comes from the west, south-west and south, falling to 25% of the time at 1500 hours. Winds from the north, north-east and east comprise 28% of the wind at 0900 hours, but increase to 52% by 1500 hours (based on data for Moruya Heads – MHL516 1988). The most dominant wave approach is from the south to east about 80% of the time. Significant wave height range is 1 – 2 m with the month of June typically having the most severe wave climate.

Outfall Site

The Ladders

(Ladd_5) Last updated June 2000