The relationship between sedimentation on Aldinga Reef, and Washpool Creek and Sellicks Creek catchments, Willunga Basin

Abstract

This study assesses the relationship between sediment accumulation on Aldinga Reef in Gulf St. Vincent, and sediment discharges from two neighbouring rural catchments, Washpool Creek and Sellicks Creek, in the Willunga Basin, South Australia. Since European settlement, extensive woodland clearance, the introduction of plant species, and intensive agricultural activities have been major features of the Basin's environment. As a result erosion and gullying have been prevalent in the two catchments. The study compares patterns of erosion as noted from field observations, with analysis of a sediment core from a lagoon in Washpool Creek catchment. The palaeoecological approach was undertaken to investigate changes in vegetation, erosion and sedimentation associated with European land use practices on the rural catchment. Field observations indicated that erosion and gullying was greatest in Sellicks Creek catchment. Lead-210 dating of Washpool Lagoon sediments indicated that the rate of sedimentation was not as great as was expected from a catchment experiencing such severe erosion and gullying. The calculated 210pb flux indicated that sediment discharges from Wasbpool Creek catchment to the Gulf of St. Vincent were only negligible.