Morphology of estuarine bedforms, Weser Estuary, Germany
Morphology of estuarine bedforms, Weser Estuary, Germany
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DOI：
10.1002/esp.5243
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发表时间：
2021-09
影响因子：
3.3
通讯作者：
A. Lefebvre;G. Herrling;M. Becker;Anna C. Zorndt;K. Krämer;C. Winter
中科院分区：
文献类型：
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作者：
A. Lefebvre;G. Herrling;M. Becker;Anna C. Zorndt;K. Krämer;C. Winter
大型底形（沙丘）存在于许多浅水环境中。河流和沿海管理需要了解其规模和动态。在感潮河流和河口，水动力（由河流和潮流的作用产生）、泥沙输运和底形大小之间的相互作用是复杂的。对德国威悉河河口底形的分布和形态进行了研究。在2009年至2013年期间，在沿着航道的每月多波束回声测深仪调查的测深数据中确定了底形。它们的大小和形状进行了表征。底形存在沿着大部分的通道，除了在河口最大浑浊度的位置，并进行疏浚。平均床型长度在20 ~ 60 m之间，床型高度在0.3 ~ 1.6 m之间。底形不对称性在空间和时间上沿着河口变化。在河流流量高的时候，底形通常比流量低的时候更不对称。底形主要是二维低角度沙丘，其最陡的坡度位于底形顶部附近。相当大比例的底形具有陡峭的表面（背风面部分陡于15°）。这意味着它们可能产生流动分离和湍流尾流，并有很大的可能引起高床面粗糙度。然而，重要的变化，陡峭的脸面积密度，注意到，无论是空间沿着河口和时间的潮汐相位（落潮或洪水）和河流流量的季节性变化的函数。研究结果对河口水动力学和泥沙输运的理解和模拟具有广泛的意义。
Large bedforms (dunes) are present in many shallow‐water environments. Knowledge of their dimensions and dynamics is required for river and coastal management. In tidal rivers and estuaries, the interaction among hydrodynamics (which results from the action of river and tidal flows), sediment transport and bedform shape and size is complex. In the present study, the distribution and morphology of bedforms in the Weser Estuary, Germany, were investigated. Bedforms were identified in bathymetric data of monthly multibeam echosounder surveys along the navigation channel during the years 2009 to 2013. Their size and shape were characterized. Bedforms were present along most of the channel, except at the position of the estuarine turbidity maximum and where dredging is carried out. Average bedform length varied between 20 and 60 m and bedform height between 0.3 and 1.6 m. Bedform asymmetry varied spatially and temporally along the estuary. In times of high river discharge, bedforms were generally more ebb‐asymmetric than in times of low discharge. The bedforms were predominantly two‐dimensional low‐angle dunes with their steepest slope situated near the bedform crest. A significant proportion of bedforms possessed a steep face (portion of the lee side steeper than 15°). This implies that they are likely to create flow separation and a turbulent wake, with a strong potential to induce high bedform roughness. However, important variations in steep face area density were noted, both spatially along the estuary and temporally as a function of the tidal phase (ebb or flood) and the seasonal variation in river discharge. The results have wide implications in terms of understanding and modelling hydrodynamics and sediment transport in estuaries.