The twin breakwaters constructed at the entrance to the Brunswick River effectively created a new headland. 1 Where the scale of the breakwater is larger than the local wavelength, the perturbation will alter local wave transformation patterns thereby inducing a re-alignment of sandy foreshores. Mobile bed scale modelling has demonstrated conclusively that breakwaters can change beach alignments by creating artificial headlands, forming crenulated bays on what previously were linear shorelines. This has resulted in the construction of expensive sand-bypassing systems and revetments to offset their impacts. The Tweed breakwaters have trapped sand, taking it out of the littoral system through the accretion of Letitia Spit, causing coastal erosion on the Gold Coast. Although this improved navigation for a period, the entrance bar reformed and again created difficulties for navigation. These works culminated in the extension of the training walls at the river entrance to form breakwaters. River training works and dredging have been undertaken at the Tweed River in attempt to improve navigability. These effects can be seen right along the NSW coast of Australia, where breakwaters and training walls have been implemented. This has induced long-term changes to foreshore alignments, tidal currents, tidal planes and marine ecologies, with significant consequences. Across the eastern seaboard of Australia, breakwaters and training walls have instigated fundamental perturbations to coastal and estuary processes.
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