Coupling cross-shore and longshore sediment transport to model storm response along a mixed sand-gravel coast under varying wave directions
Coupling cross-shore and longshore sediment transport to model storm response along a mixed sand-gravel coast under varying wave directions
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DOI：
10.1016/j.coastaleng.2017.09.009
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发表时间：
2017-11
影响因子：
4.4
通讯作者：
R. Bergillos;G. Masselink;M. Ortega-Sánchez
中科院分区：
文献类型：
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作者：
R. Bergillos;G. Masselink;M. Ortega-Sánchez
本文研究了西班牙南部Playa Granada砂砾混合三角洲海滩在不同方向风暴波作用下的剖面响应。在不同的波浪条件下，对海滩地形进行了36天的监测，并将剖面响应与使用XBeach-G模型和沿岸沉积物传输(LST)公式的模型预测进行了比较。在两天的低能量、西南(西南)风暴和东南(SE)风暴条件下应用了XBeach-G，并使用参数方法将LST耦合到LST，该方法将LST分布在冲浪、海浪和近岸区域。用一个定标的波传播模型(Delft3D)获得了驱动XBeach-G模型和LST公式所需的近岸条件。风暴响应明显受自由面(护堤高度与总高度之差)和风浪方向的影响，西南风暴侵蚀测区，东南风暴造成海滩淤积。模式模拟结果表明，由于研究区LST梯度较高，在西南风暴(B S、S和GT；0.95)条件下，X海滩-G本身能够较好地再现海滩的响应，但在东南风暴条件下则不能。在西南(B S S)和东南部(B S S)两个风暴下，XBASE-G和LST的组合都能很好地拟合实测剖面，从而激发了人们对耦合模式在不同波浪条件下预报风暴响应的信心。在整个6.8公里三角洲海岸线上应用了XBASTABASE-G/LST联合模式，以研究极端西南和东南风暴事件的影响，模式结果重申了跨岸和沿岸泥沙输送在驱动该位置海岸风暴响应方面的重要性。这项工作中提出的方法可以推广到受跨岸和沿岸泥沙运动影响很大的其他世界海岸，例如具有不同海岸线方向和/或受不同波浪方向强迫的海滩。
This paper investigates the profile response of a mixed sand-gravel deltaic beach (Playa Granada, southern Spain) forced by storm waves from varying directions. Beach morphology was monitored over a 36-day period with variable wave conditions, and profile response was compared to model predictions using the XBeach-G model and a longshore sediment transport (LST) formulation. XBeach-G was applied over 2-day periods of low energy, south-westerly (SW) storm and south-easterly (SE) storm conditions, and was coupled to LST using a parametric approach which distributes the LST across the swash, surf and nearshore zones. A calibrated wave propagation model (Delft3D) was used to obtain the inshore conditions required to drive the XBeach-G model and the LST formulation. The storm response is clearly influenced by the free-board (difference between the height of the berm and the total run-up) and is also strongly dependent on storm-wave direction, with the SW storm eroding the surveyed area, while the SE storm induced beach accretion. Model results indicate that XBeach-G on its own is capable of adequately reproducing the response of the beach under SW storm conditions (B S S> 0.95), but not under SE storms due to the higher LST gradients at the study location. The combination of XBeach-G and LST fits the measured profiles reasonably well under both SW (B S S> 0.96) and SE (B S S> 0.88) storms, inspiring confidence in the coupled model to predict the storm response under varying wave conditions. The combined XBeach-G/LST model was applied to the entire 6.8-km deltaic coastline to investigate the impact of extreme SW and SE storm events, and the model results reiterate the importance of cross-shore and longshore sediment transport in driving coastal storm response at this location. The approach proposed in this work can be extended to other worldwide coasts highly influenced by both cross-shore and longshore sediment transport, such as beaches with different coastline orientations and/or forced by varying wave directions.