Quantifying overwash in a laboratory experimental analysis using bichromatic waves

IF 4.5 2区工程技术 Q1 ENGINEERING, CIVIL

Coastal Engineering Pub Date : 2025-09-02 DOI:10.1016/j.coastaleng.2025.104869

Jana Echave Lezcano, Colin Whittaker, Giovanni Coco

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引用次数: 0

Abstract

Overwash influences dune resilience and sediment transport, yet the physical parameters governing this process remain poorly understood due to complex hydrodynamic and morphodynamic interactions. This study investigates how broad and narrow-band wave groups and water level variations govern the feedback between overwash dynamics and dune morphological response. Three overwash scenarios were identified: (1) early-stage overwash, where the system begins in overwash and transitions to collision; (2) intermittent overwash; and (3) persistent overwash, characterised by stronger onshore sediment transport.

Results indicate that small initial water level variations (

<

4% of the water depth) can significantly influence overwash intensity and frequency, with the highest tested water level (0.775 m) producing the most persistent overwash conditions. Longer wave groups enhance overwash initiation by maintaining elevated infragravity swash across successive waves, increasing the likelihood of crest exceedance. In contrast, shorter groups generate more frequent individual runup events that interact with the dune, increasing overwash occurrences. However, under high water levels, wave group effects become secondary.

The Overwash Potential (OP) metric is assessed as an indicator of overwash occurrence. Findings show that threshold values between collision and overwash are scale-dependent, requiring calibration to reflect dune freeboard effects accurately. Additionally, OP estimation is highly sensitive to the beach slope definition; using a non-representative slope can underestimate OP exceedance, overwash frequency, and severity.

Future laboratory studies should treat water level as a key design parameter and incorporate long-term morphological feedback and field-scale validation. These steps will improve predictive model accuracy and inform the development of effective coastal resilience strategies under extreme conditions.

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用双色波定量实验室实验分析中的过洗

冲过影响沙丘恢复力和沉积物输运，但由于复杂的水动力和形态动力相互作用，控制这一过程的物理参数仍然知之甚少。本研究探讨了宽、窄带波群和水位变化如何控制冲积动力和沙丘形态响应之间的反馈。确定了三种过冲情景：(1)早期过冲，系统从过冲开始过渡到碰撞；(2)间歇过洗；(3)持续的冲过，以更强的陆上沉积物输送为特征。结果表明，较小的初始水位变化（<；4%的水深）可以显著影响过冲强度和频率，最高测试水位（0.775 m）产生的过冲条件最持久。较长的波群通过在连续的波之间保持较高的次重力冲刷，增加了波峰超越的可能性，从而增强了过冲的开始。相比之下，较短的群体会产生更频繁的个体上升事件，与沙丘相互作用，增加溢水的发生。然而，在高水位下，波群效应是次要的。过冲电位（OP）指标被评估为过冲发生的一个指标。研究结果表明，碰撞和冲过之间的阈值与尺度有关，需要校准才能准确反映沙丘干舷效应。此外，OP估计对海滩坡度定义高度敏感；使用非代表性斜率可能会低估OP超标、过洗频率和严重程度。未来的实验室研究应将水位作为关键的设计参数，并结合长期的形态反馈和现场规模验证。这些步骤将提高预测模型的准确性，并为在极端条件下制定有效的沿海恢复策略提供信息。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Coastal Engineering 工程技术-工程：大洋

CiteScore

9.20

自引率

13.60%

发文量

审稿时长

3.5 months

期刊介绍： Coastal Engineering is an international medium for coastal engineers and scientists. Combining practical applications with modern technological and scientific approaches, such as mathematical and numerical modelling, laboratory and field observations and experiments, it publishes fundamental studies as well as case studies on the following aspects of coastal, harbour and offshore engineering: waves, currents and sediment transport; coastal, estuarine and offshore morphology; technical and functional design of coastal and harbour structures; morphological and environmental impact of coastal, harbour and offshore structures.