Modeling the growth and migration of sandy shoals on ebb‐tidal deltas
Modeling the growth and migration of sandy shoals on ebb‐tidal deltas
复制标题
模拟退潮三角洲沙洲的生长和迁移
DOI：
10.1002/2016jf003823
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
P. Hoekstra
中科院分区：
文献类型：
--
作者：
W. Ridderinkhof;H. Swart;M. Vegt;P. Hoekstra
在许多退潮三角洲上可以观察到向下漂流海岸迁移的连贯的沙质浅滩。在这项研究中，确定了导致落潮三角洲浅滩生长和迁移的过程。此外，还研究了入射波能和进水口的潮汐棱柱对这些浅滩迁移速度的影响。为此，采用了具有理想几何结构的数值地貌动力学模型。该模型计算了潮汐和波浪驱动的沙粒局部冲刷和淤积引起的河床水位演变。对模型结果的分析表明，当水深和波浪条件之间存在局部不平衡时，浅滩就会生长，在本研究中，这种不平衡是通过人工破坏落潮三角洲或在波浪强迫的基础上增加风暴造成的。浅滩形成的门槛取决于沙粒的分布和入射波能。浅滩上的波浪折射导致了波浪能量的集中，并增加了局部最小水深位置附近的波浪能量耗散。这在浅滩上产生了残余水流，并增加了向当地最小水深方向的侧摩阻力，共同形成了一种沙粒输送模式，诱导了浅滩的生长和迁移。不对称波浪引起的泥沙输运有助于保持浅滩的连贯结构。浅滩的迁移速度随着入射波能量的增加和潮汐棱柱的减小而增加，这是因为潮汐残流与引起浅滩迁移的波浪驱动的残流相反。
Coherent sandy shoals that migrate toward the downdrift coast are observed on many ebb‐tidal deltas. In this study, processes that cause the growth and migration of shoals on ebb‐tidal deltas are identified. Moreover, the effect of the incident wave energy and the tidal prism of an inlet on the migration speed of these shoals is investigated. For this, a numerical morphodynamic model with an idealized geometric setup is employed. The model computes the bed level evolution due to local erosion and deposition of sand driven by tides and waves. Analysis of model results shows that shoals grow when there is a local imbalance between the bathymetry and the wave conditions, which in this study was imposed by manually breaching the ebb‐tidal delta or by adding storms to the wave forcing. There are thresholds for shoal formation that depend on the distribution of the sand and the incident wave energy. Wave refraction over the shoals leads to focusing of wave energy and increased wave energy dissipation around the location of the local minimum water depth. This generates residual currents over the shoal and increased skin friction toward the local minimum water depth, which together create a sand transport pattern that induces the growth and migration of the shoal. Sand transport due to asymmetric waves contributes to keeping the shoal a coherent structure. The shoal migration speed increases with increasing incident wave energy and decreasing tidal prism; this is because tidal residual currents oppose the wave‐driven residual currents that cause shoal migration.
DOI：
10.1016/j.ecss.2006.06.021
发表时间：
2006-10
期刊：
Estuarine, coastal and shelf science
影响因子：
--
作者：
J. Fiechter;Kelley Steffen;C. Mooers;B. Haus
通讯作者：
J. Fiechter;Kelley Steffen;C. Mooers;B. Haus
影响因子：
3.9
作者：
G. Herrling;C. Winter
通讯作者：
G. Herrling;C. Winter