Notch development at the base of sea cliffs is an important control on cliff recession rates, but a detailed mechanistic understanding of notch formation by swash abrasion is lacking. We conducted physical experiments, using homogeneous erodible rock simulants, to study notch-forming mechanisms under periodic sediment-laden bore impacts. Our findings reveal shifts in the temporal dynamics of notch development. Initially, swash uprush and vortex formation contribute to a positive feedback loop that creates a shallow and wide notch. Subsequently, upward erosion ceases, and notch backwear and downwear are dominated by the vortex. Eventually, sediment deposition armors the notch floor; this negative feedback loop reduces erosion. The sediment size determines the amount of erosion, with a range of grain sizes generating maximum erosion. This indicates a dependence on the momentum of the sediment particles entrained within the bore. This research reveals fundamental notch formation mechanisms driven by swash abrasion.

中文翻译：

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斜面磨损造成的悬崖缺口：物理实验的见解


海崖底部的凹口发育是控制悬崖衰退率的重要因素，但缺乏对斜面磨损形成凹口的详细机制理解。我们使用均质的易蚀岩石模拟物进行了物理实验，以研究周期性充满沉积物的孔冲击下的缺口形成机制。我们的研究结果揭示了缺口发育的时间动态变化。最初，旋转盘上升和涡流形成有助于形成一个浅而宽的凹口的正反馈回路。随后，向上侵蚀停止，凹口上衣和下衣由涡流主导。最终，沉积物沉积在凹口底部上。这种负反馈循环减少了侵蚀。沉积物的大小决定了侵蚀的程度，不同的颗粒大小会产生最大的侵蚀。这表明依赖于孔内夹带的沉积物颗粒的动量。这项研究揭示了由斜面磨损驱动的基本凹口形成机制。