The role of river flow and tidal asymmetry on 1-D estuarine morphodynamics
The role of river flow and tidal asymmetry on 1-D estuarine morphodynamics
复制标题
河流流量和潮汐不对称对一维河口形态动力学的作用
DOI：
10.1002/2014jf003110
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发表时间：
2014-11-01
影响因子：
3.9
通讯作者：
He, Q.
中科院分区：
文献类型：
--
作者：
Guo, L.;van der Wegen, M.;He, Q.
许多研究工作致力于了解潮汐强迫下的河口地貌动力学。然而，河流流量对河口地貌动力学的影响还没有得到充分的研究。本文以长江口为研究对象，基于Delft 3D一维模型，探讨了长江口560 km长的潮汐流域内河流流量对潮汐动力地貌的影响。该模型考虑了总输沙量，并采用了形态动力更新方案，以实现长期的形态动力演变。我们分析了斯托克斯漂移，潮汐不对称，河流流量在产生潮汐剩余泥沙输运的作用。模型结果表明，形态动力学平衡接近千年内消失的潮汐剩余泥沙输运的空间梯度。我们发现，退潮导向斯托克斯回流/河流与潮汐之间的相互作用是一个重要的机制，冲刷河流提供的泥沙向海。河流流量的增加不会引起连续的侵蚀或加积平衡床的轮廓，因为河流泥沙供应和泥沙冲入海之间的平衡。可以定义一个中间阈值河流流量，它导致最深的平衡床剖面。因此，平衡床剖面的形状（凸形或凹形）将与河流流量的大小相适应。总的来说，本研究揭示了河流流量在控制河口地貌动力学的重要作用，通过提供泥沙和加强潮落方向的剩余泥沙输运。
Numerous research efforts have been devoted to understanding estuarine morphodynamics under tidal forcing. However, the impact of river discharge on estuarine morphodynamics is insufficiently examined. Inspired by the Yangtze Estuary, this work explores the morphodynamic impact of river discharge in a 560 km long tidal basin based on a 1-D model (Delft3D). The model considers total load sediment transport and employs a morphodynamic updating scheme to achieve long-term morphodynamic evolution. We analyze the role of Stokes drift, tidal asymmetry, and river discharge in generating tidal residual sediment transport. Model results suggest that morphodynamic equilibrium is approached within millennia by vanishing spatial gradients of tidal residual sediment transport. We find that the interaction between ebb-directed Stokes return flow/river flow with tides is an important mechanism that flushes river-supplied sediment seaward. Increasing river discharge does not induce continuously eroded or accreted equilibrium bed profiles because of the balance between riverine sediment supply and sediment flushing to the sea. An intermediate threshold river discharge can be defined which leads to a deepest equilibrium bed profile. As a result, the shape (concavity or convexity) of the equilibrium bed profiles will adapt with the magnitude of river discharge. Overall, this study reveals the significant role of river discharge in controlling estuarine morphodynamics by supplying sediment and reinforcing ebb-directed residual sediment transport.