Tidal and intra-tidal sand transport processes across a macrotidal intertidal zone, Broome, Western Australia: Implications for measurements of sand transport associated with coastal developments

Sand transport was measured in the shallow subtidal zone of a macrotidal, seasonally waveinfluenced tropical setting, at Broome, northwest Australia, to inform the design of a proposed boating facility. For five weeks, waves and currents were measured in the subtidal zone, with LISST-100x and LISST-STx
instruments measuring in-situ particle size distributions (PSD) and settling velocities of mobilized sediment. Boat-based vertical profiles taken on the faster and longer ebb tide revealed very strong vertical gradients in PSD (sand concentrations in the basal 40 cm of 20-30 times that 1 m above bed and higher) and indicated some variation potentially due to the turbulent bursting process. The LISST in-situ particle size data was invaluable in understanding the sedimentary processes, assessing the uncertainties and lending weight to the conclusions. The potential long-term rate of sand flux was calculated to be ∼200,000 m3/yr towards the SSW, which, even taking the uncertainties into account, was likely to prove unmanageable in practical terms