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首页> 外文期刊>Journal of Geophysical Research, C. Oceans: JGR >Lateral entrapment of sediment in tidal estuaries: An idealized model study
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Lateral entrapment of sediment in tidal estuaries: An idealized model study

机译：潮汐河口泥沙的侧向截留：理想化模型研究

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摘要

Two physical mechanisms leading to lateral accumulation of sediment in tidally dominated estuaries are investigated, involving Coriolis forcing and lateral density gradients. An idealized model is used that consists of the three-dimensional shallow water equations and sediment mass balance. Conditions are assumed to be uniform in the along-estuary direction. A semidiurnal tidal discharge and tidally averaged density gradients are prescribed. The erosional sediment flux at the bed depends both on the bed shear stress and on the amount of sediment available in mud reaches for resuspension. The distribution of mud reaches over the bed is selected such that sediment transport is in morphodynamic equilibrium, that is, tidally averaged erosion and deposition of sediment at the bed balance. Analytical solutions are obtained by using perturbation analysis. Results suggest that in most estuaries lateral density gradients induce more sediment transport than Coriolis forcing. When frictional forces are small (Ekman number E < 0.02), the Coriolis mechanism dominates and accumulates sediment on the right bank (looking up-estuary in the Northern Hemisphere). On the other hand, when frictional forces are moderate to high (E > 0.02), the lateral density gradient mechanism dominates and entraps sediment in areas with fresher water. Results also show that the lateral sediment transport induced by the semidiurnal tidal flow is significant when frictional forces are small (E ～ 0.02). Model predictions are in good agreement with observations from the James River estuary.
机译：研究了导致潮汐主导的河口沉积物横向积聚的两种物理机制，包括科里奥利强迫和横向密度梯度。使用的理想模型由三维浅水方程和沉积物质量平衡组成。假设条件在沿河口方向是一致的。规定了半日潮汐流量和潮汐平均密度梯度。河床的侵蚀性泥沙通量既取决于河床的剪切应力，也取决于泥浆中可用于重悬的泥沙量。选择泥浆在床层上的分布，以使泥沙运移处于形态动力学平衡状态，即潮汐平均侵蚀和泥沙在床层平衡处的沉积。通过使用扰动分析获得解析解。结果表明，在大多数河口，横向密度梯度比科里奥利斯强迫引起的泥沙输送更多。当摩擦力较小（Ekman数E <0.02）时，科里奥利机制占主导地位，并在右岸（北半球的上河口向上）堆积沉积物。另一方面，当摩擦力从中到高（E> 0.02）时，横向密度梯度机制将占主导地位，并在水较浅的区域截留沉积物。结果还表明，当摩擦力较小时（E〜0.02），半昼间潮汐水流引起的侧向泥沙运移很明显。模型的预测与詹姆斯河河口的观测非常吻合。

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