RED POINT OUTFALL

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Physical Environment

Landscape

The Illawarra region lies stratigraphically at the top of the Permian Shoalhaven group of rocks, which consist of interbedded siltstones, sandstones and shales with various intrusive igneous rocks of the Gerringong Volcanic Facies. Red Point is a seaward extension of Gerringong Volcanic rocks that consist of intrusive and extrusive latite (Wollongong Geological Series Sheet SI 56-9). Red Point marks a geological boundary between sandy seabed to the south-west of the Point (Perkins Beach) and rock and gravel seabed to the east and north of the Point. Extensive reefs and rocky outcrops occur around Red Point and the Five Islands group of islands are found offshore and to the north-east of Red Point.

Bathymetry & Substrate

The outfall is located on the south-east side of Red Point at the near vertical edge of a rocky reef platform and discharges subtidally in approximately 8m of water. To the south of the outfall are low relief, rocky cliffs of Red Point and then Perkins Beach. To the north is Fishermans Beach, a small rocky headland, North Beach and then Port Kembla Harbour.
Currents, Winds and Waves

Climate, wind and oceanographic data for the area are available from AWT (1992a) and Patterson, Britton & Partners, CEE & AWT (1998). These studies indicate:

- currents generally flowed to the south, but northerly flow was experienced 10-20% of the time.

- currents towards the south tended to be stronger in the summer months (February to March).

- about half the time there appeared to be significant water movement suggested to be due to coastally trapped waves. Current speeds associated with these waves was about 0.2 to 0.3 m/s to north or south with a variable period (typically 3-10 days).

- there were no clear patterns between the winds and water movement.

- wind directions in the nearshore environment were significantly affected by the locally complex land topography.

- in nearshore studies, the east Australian current was rarely observed (less than 10% of the time).

- from the August 1991experiment, there was clear evidence of secondary circulation cells in the lee of the islands (Five Islands) near Port Kembla. These cells reached a diameter of 4km and produced current speeds of approximately 0.1m/s. these cells appeared to be transient, but have the potential to move effluent towards the shore.

- the islands offshore of Port Kembla created a major restriction to the dominant southerly flow, diverting the flow offshore. This resulted in onshore currents in this region and a net northerly current in the channel between Red Point (the site of the outfall) and Rocky Island.

- Recent studies by Lawson and Treloar (1998 cited by Patterson Britton & Partners, CEE & AWT 1998) at the proposed deep water outfall site off Coniston Beach indicate:

- a net current to the south of 4 cm/s.

- southerly currents occurred much more frequently than northerly currents, which in turn occurred more frequently than offshore/onshore currents.

- currents measured over a one month period revealed that they were generally weak, with longshore currents averaging 4cm/s and onshore/offshore currents averaging 2cm/s.

Outfall Site

Outfall Site

Outfall Site

Outfall Site

Red Point

(Redp_5) Last updated June 2000