Understanding coastal morphodynamic patterns from depth‐averaged sediment concentration
Understanding coastal morphodynamic patterns from depth‐averaged sediment concentration
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DOI：
10.1002/2014rg000457
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发表时间：
2015-06
影响因子：
25.2
通讯作者：
F. Ribas;A. Falqués;H. Swart;N. Dodd;R. Garnier;D. Calvete
中科院分区：
文献类型：
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作者：
F. Ribas;A. Falqués;H. Swart;N. Dodd;R. Garnier;D. Calvete
本文着重介绍了深度平均泥沙浓度(DASC)在理解一些具有近岸韵律模式的海岸地貌动力特征的形成中的重要作用：海滩尖端、冲浪带横向和新月形沙洲以及与海岸相连的沙脊。我们提出了一种基于DASC(等于泥沙负荷除以水深)的知识的公式和方法，该公式和方法已成功地用于理解这些特征的特征。这些砂体与海岸工程和其他学科相关，位于海岸带的不同部分，具有不同的空间和时间尺度，但可以使用相同的技术来理解它们。由于砂体是在深度平均流存在的情况下形成的，因此泥沙输移大约等于泥沙负荷乘以水流。此外，还假定波浪基本上会移动沉积物，而海流会增加这种移动并使沉积物平流。在这种情况下，知道DASC的空间分布和由强迫(波、风和气压梯度)引起的深度平均流可以推断泥沙输送的收敛/发散。当电流从DASC的高到低(低到高)值区域流动时，就会发生沉积(侵蚀)。该公式和方法对于理解流动和形态之间的正反馈机制导致这些形态特征的形成特别有用，但也可以探索它们迁移的物理机制、它们的有限振幅行为和它们的衰变。
This review highlights the important role of the depth‐averaged sediment concentration (DASC) to understand the formation of a number of coastal morphodynamic features that have an alongshore rhythmic pattern: beach cusps, surf zone transverse and crescentic bars, and shoreface‐connected sand ridges. We present a formulation and methodology, based on the knowledge of the DASC (which equals the sediment load divided by the water depth), that has been successfully used to understand the characteristics of these features. These sand bodies, relevant for coastal engineering and other disciplines, are located in different parts of the coastal zone and are characterized by different spatial and temporal scales, but the same technique can be used to understand them. Since the sand bodies occur in the presence of depth‐averaged currents, the sediment transport approximately equals a sediment load times the current. Moreover, it is assumed that waves essentially mobilize the sediment, and the current increases this mobilization and advects the sediment. In such conditions, knowing the spatial distribution of the DASC and the depth‐averaged currents induced by the forcing (waves, wind, and pressure gradients) over the patterns allows inferring the convergence/divergence of sediment transport. Deposition (erosion) occurs where the current flows from areas of high to low (low to high) values of DASC. The formulation and methodology are especially useful to understand the positive feedback mechanisms between flow and morphology leading to the formation of those morphological features, but the physical mechanisms for their migration, their finite‐amplitude behavior and their decay can also be explored.