Waves and water level setup during storms can create overwashing flows across barrier islands. Overwashing flows can cause erosion, barrier breaching, and inlet formation, but their sediments can also be deposited and form washover fans. These widely different outcomes remain difficult to predict. Here we suggest that a breach develops when the sediment volume transported by overwashing flows exceeds the barrier subaerial volume. We form a simple analytical theory that estimates overwashing flows from storm characteristics, barrier morphology, and dune vegetation, and which can be used to assess washover deposition and breaching likelihood. Our theory suggests that barrier width and storm surge height are two important controls on barrier breaching. We test our theory with the hydrodynamic and morphodynamic model Delft3D as well as with field observations of 21 washover fans and 6 breaches that formed during Hurricane Sandy. There is reasonable correspondence for natural but not for developed barrier coasts, where traditional sediment transport equations do not readily apply. Our analytical formulations for breach formation and overwash deposition can be used to improve long-term barrier island models.

中文翻译：

---

屏障破坏与过冲沉积：预测风暴对沿海屏障的形态影响

风暴期间的波浪和水位设置可能会造成跨障岛的过冲水流。过冲流会导致侵蚀、屏障破坏和入口形成，但它们的沉积物也可以沉积并形成冲刷扇。这些截然不同的结果仍然难以预测。在这里，我们建议当冲刷流输送的沉积物体积超过屏障地下体积时，就会出现裂缝。我们形成了一个简单的分析理论，可以根据风暴特征、屏障形态和沙丘植被估计冲刷流量，并可用于评估冲刷沉积和破坏可能性。我们的理论表明，屏障宽度和风暴潮高度是屏障突破的两个重要控制因素。我们使用流体动力学和形态动力学模型 Delft3D 以及对飓风桑迪期间形成的 21 个冲刷风扇和 6 个裂缝的现场观察来测试我们的理论。自然的但不是发达的屏障海岸有合理的对应关系，传统的沉积物输送方程不容易适用。我们用于裂缝形成和过冲沉积的分析公式可用于改进长期屏障岛模型。