Abstract Embayed beaches are highly attractive sandy beaches bounded laterally by rigid boundaries, which deeply affect equilibrium beach planform and shoreline dynamics. We use LX-Shore, a state-of-the-art shoreline change model coupled with a spectral wave model to address embayed beach shoreline dynamics driven by longshore sediment transport processes. The model is applied to different idealized embayed beach configurations including variations in headland lengths. The model simulates a large range of equilibrium embayed beach planforms and associated spatial and temporal modes of shoreline variability. For short headlands enabling occasional headland sand bypassing, both embayed beach curvature and maximum erosion at the upwave side of the embayment increases with increasing headland length. Beach curvature also increases with increasing headland length for headlands long enough to prevent any headland sand bypassing. In contrast, at the same time, embayed beach becomes increasingly curved and symmetric, with maximum localised erosion within the embayment decreasing in intensity. When there is no headland sand bypassing, rotation signal decreases in amplitude and becomes increasingly symmetric with increasing headland length. The modal (time-invariant) directional spreading of incident waves is critical to embayed beach behaviour, with the envelope and variance of cross-shore shoreline change and time-averaged shoreline curvature all increasing with decreasing modal directional spreading. Embayed beach rotation characteristic timescale increases with increasing embayed beach length, while the narrower the embayment the smaller the cross-shore amplitude of shoreline variability. Our simulations provide new insight into the influence of embayment characteristics and incident wave conditions on equilibrium planform and shoreline dynamics of embayed beaches. This work also implies that the degree of potential headland sand bypassing should be taken into account for modelling of beach rotational dynamics and embayed beach dynamic planform configuration.

中文翻译：

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海湾海滩平衡平面和旋转信号的建模

摘要 Embayed海滩是由刚性边界横向包围的极具吸引力的沙滩，深刻影响平衡海滩平面和海岸线动力学。我们使用 LX-Shore，这是一种最先进的海岸线变化模型，结合光谱波模型来解决由沿岸沉积物运输过程驱动的海湾海滩海岸线动力学问题。该模型应用于不同的理想化海滩配置，包括岬角长度的变化。该模型模拟了大范围的平衡海滩平面图和相关的海岸线变化的空间和时间模式。对于偶尔会绕过岬角沙子的短岬角，海湾上浪侧的海湾海滩曲率和最大侵蚀都随着岬角长度的增加而增加。海滩曲率也随着岬角长度的增加而增加，因为岬角足够长以防止任何岬角沙子绕过。相比之下，同时，海湾海滩变得越来越弯曲和对称，海湾内最大的局部侵蚀强度减弱。当没有岬角沙子绕过时，旋转信号的幅度减小并且随着岬角长度的增加而变得越来越对称。入射波的模态（时不变）方向传播对于海湾海滩行为至关重要，跨海岸海岸线变化和时间平均海岸线曲率的包络和方差都随着模态方向传播的减少而增加。Embayed 海滩旋转特征时间尺度随着 embayed 海滩长度的增加而增加，而海湾越窄，海岸线变化的跨岸幅度越小。我们的模拟为海湾特征和入射波条件对海湾海滩的平衡平面和海岸线动力学的影响提供了新的见解。这项工作还意味着，在对海滩旋转动力学和海湾海滩动态平面配置进行建模时，应考虑潜在的岬角绕沙程度。