There is a long history of erosion at Old Bar Beach, which is characterised by some of the highest recession rates on the NSW coast. With significant threats to coastal properties at Old Bar, Greater Taree City Council (Council) and the NSW Office of Environment and Heritage (OEH) investigated structural options available to protect development. While a rock revetment could protect property, it became clear that this could have a greater impact on beach amenity. A possible solution to preserve beach amenity involves beach nourishment, however a better understanding of the complex sediment transport processes in the region is required to fully assess the feasibility of any beach nourishment strategy. Understanding the sediment transport pathways and loss mechanisms is also critical for assessing the feasibility of other possible coastal protection strategies.

Working with OEH and MidCoast Water, Council engaged Royal HaskoningDHV and ETS to undertake a sand tracing study aimed at improving the understanding of sediment transport processes at Old Bar Beach. The first step involved the deployment of different coloured fluorescent sand tracer material at three locations on Old Bar Beach. Over the next 12 months four sampling exercises were undertaken within both the onshore and offshore environments. The collected samples were subsequently analysed to assess the transport of the tracer material under the local coastal processes.

Clearly identifiable longshore and cross-shore sediment transport pathways were identified from the analysis results. This provides an improved conceptual understanding of sediment transport processes at Old Bar Beach for a range of wave conditions including low energy, significant storm activity, and post-storm beach recovery. The results from the sand tracing study will provide greater certainty to Council and the local community regarding the selection and design of possible coastal management options at Old Bar Beach.

Sand tracing is starting to gain traction in Australia as an innovative and valuable tool for determining effective coastal management strategies.

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Patrick Lawless

Sydney, AU

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