Estuarine beaches are ubiquitous, yet understudied, coastal systems. The mixed hydrodynamic processes – such as combined tidal and wave forcing – and the influence of adjacent sedimentary features – such as flood-tide deltas (FTDs) – leads to complex morphodynamic processes. As such, the dynamics and evolution of these important coastal systems are poorly understood. This study synthesises a set of analyses conducted on an estuarine beach, in southeast Australia, over multiple temporal scales. Nearshore waves and currents were measured and used to determine the processes driving seasonal to yearly beach change between 2007 and 2010. These results were compared to decadal scale beach change determined from aerial photos between 1963 and 2006. We found the westward transport of sediment towards the inner estuary was the dominant nearshore process leading to erosion in the eastern regions of the beach (near the estuary entrance) and accretion in the west over yearly time scales. Cross-shore sediment transport occurred during winter storm swell conditions leading to erosion in more exposed sites and some limited accretion in sheltered zones, most likely due to sediment input from the flood-tide delta. However, severe storm swell events that propagated into the estuary led to a loss of sediment and erosion across the entire beach which was not recovered during the study period. It is likely that the erosion processes observed in the short- to medium-term (days to years) analyses are the conditions that led to the long-term shoreline retreat observed in the aerial photograph record. The long-term shoreline retreat since 1963 is likely a result of a negative sediment balance due to movement of the FTD and a lack of sediment input in the eastern regions of Shoal Bay. Shoreline retreat will likely continue unless increased sediment input occurs from marine sources or shoreline interventions are maintained.

河口海滩是无处不在但尚未被研究的沿海系统。混合的水动力过程（例如，潮汐和波浪强迫相结合）以及邻近沉积特征的影响（如潮汐三角洲（FTD））导致复杂的地貌动力学过程。因此，人们对这些重要的沿海系统的动态和演化知之甚少。这项研究综合了在多个东南尺度上在澳大利亚东南部的河口海滩上进行的一组分析。对近岸海浪和洋流进行了测量，并用于确定从2007年到2010年之间从季节性到逐年海滩变化的过程。这些结果与从1963年到2006年的航拍照片确定的十年尺度海滩变化进行了比较。我们发现，沉积物向内河口的向西输送是主要的近岸过程，导致海滩东部地区（河口附近）侵蚀，并在每年的时间尺度上向西增加。跨岸沉积物运输发生在冬季风暴潮条件下，导致更多裸露的地方受到侵蚀，而庇护区的积聚量有限，这很可能是由于潮汐三角洲输入的沉积物。但是，严重的风暴潮事件扩散到河口，导致整个海滩的沉积物和侵蚀消失，在研究期间没有恢复。在中短期（几天到几年）分析中观察到的侵蚀过程很可能是导致航拍记录中观察到的长期海岸线退缩的条件。自1963年以来的长期海岸线退缩很可能是由于FTD的运动和沙洲湾东部地区缺乏泥沙输入而造成的泥沙平衡不足。除非海洋来源的沉积物输入增加或维持海岸线干预，否则海岸线退缩可能会继续。