Shellfish Reef Restoration in South Australia: Considerations for Design and Development Approvals

Shellfish reefs consisting of native oysters and mussels once thrived along the Australian coastline. These living reefs are important marine ecosystems, providing numerous environmental and social benefits. This includes the provision of food, shelter, and protection for a vast number of marine organisms, as well as key breeding habitat, assisting to maintain local fish abundance and diversity. Furthermore, the water filtering and sediment stabilisation capabilities of functional shellfish reefs improve water quality, which in turn provides tourism benefits such as improved recreational diving experiences. Various factors including commercial dredging, pollution and overfishing have decimated these important ecosystems to a point at which they are critically endangered, with less than 10% of original stocks now remaining. As such, The Nature Conservancy (TNC) have set out to restore shellfish habitats in Australia, bringing them back from the brink of extinction. Site selection and design of shellfish reefs requires careful consideration of the prevailing coastal processes and metocean conditions to ensure the long-term survival of these ecosystems and prevent adverse impacts on the surrounding environment. Jacobs provided TNC with coastal engineering expertise and advice for four shellfish reef restoration sites in South Australia (i.e. Windara, Glenelg, O'Sullivan Beach, and Kangaroo Island) to inform the design of the reefs and development applications. Engineering analyses were undertaken to investigate the likely impacts of the proposed reef structures on the prevailing coastal and shoreline processes. Recommendations for optimising the reef design were also provided, including advice on size, orientation, and rock requirements. This analysis, coupled with TNC's expertise in promoting reef ecology and diversity, led to the development and implementation of successful shellfish reefs. An overview of engineering and environmental considerations for the design and development approvals of these reefs are outlined in this paper, providing valuable learnings for future shellfish reef restorations in Australia.