Flexural Rigidity and Shoot Reconfiguration Determine Wake Length Behind Saltmarsh Vegetation Patches
Flexural Rigidity and Shoot Reconfiguration Determine Wake Length Behind Saltmarsh Vegetation Patches
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DOI：
10.1029/2019jf005012
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发表时间：
2019-08
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影响因子：
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通讯作者：
T. Marjoribanks;D. Lague;R. Hardy;R. Boothroyd;J. Leroux;C. Mony;S. Puijalon
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文献类型：
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作者：
T. Marjoribanks;D. Lague;R. Hardy;R. Boothroyd;J. Leroux;C. Mony;S. Puijalon
在沿海盐沼和河流系统等浅水环境中，植被斑块对泥沙沉积具有重要的控制作用。然而，由于斑块形态的复杂性及其与水流的动态相互作用，预测植被斑块周围的沉积是困难的。在这里，我们结合了一个生物力学模型，使用现场数据参数化，在一个三维计算流体动力学模型中，该模型允许预测由于流动强迫而导致的斑块内单个芽的重新配置。该模型预测了斑块尾迹内的速度衰减和床层剪应力，在空间上与地面激光雷达在野外测量到的吸积模式一致。将该模型应用于沿海生境盐沼中的海苔（Suaeda martima）稀疏斑块，探讨(I)枝的分布、（II）斑块的几何形状、（III）枝的弯曲刚度和（IV）体流速度对预测尾迹区长度的影响。结果表明，对于中等刚度的海苔，植被上的垂直剪切层控制了预测尾流区域的长度。因此，由于弯曲刚度引起的重构强烈影响尾流长度，混淆了斑块高度和尾流长度之间的关系。将基于弹丸重配置的简化尾迹预测模型应用于仿真数据，结果与仿真结果吻合较好。结果表明，观察到的尾迹特征可以很好地解释为弯曲刚度的种内变异性，从而证明了生物力学特征在确定流动-植被-沉积物相互作用中的重要性。
Vegetation patches play an important role in controlling sediment deposition in shallow aquatic environments such as coastal saltmarshes and fluvial systems. However, predicting deposition around vegetation patches is difficult due to the complexity of patch morphology and their dynamic interaction with the flow. Here we incorporate a biomechanical model, parameterized using field data, within a 3‐D computational fluid dynamics model which allows prediction of individual shoot reconfiguration within patches due to flow forcing. The model predicts velocity attenuation and bed shear stresses within the wake of the patch which agree spatially with accretion patterns measured in the field using terrestrial lidar. The model is applied to sparse patches of Suaeda maritima, located in saltmarshes of coastal habitats, to explore the role of (I) shoot distribution, (II) patch geometry, (III) shoot flexural rigidity, and (IV) bulk flow velocity in determining the length of the predicted wake region. We demonstrate that for Suaeda maritima, with intermediate rigidity, the vertical shear layer over the vegetation controls the length of the predicted wake region. Consequently, reconfiguration due to flexural rigidity strongly impacts on wake length, confounding the relationship between patch height and wake length. A simplified model for predicting wake length based on shoot reconfiguration is applied to the simulation data and shows good agreement. The results demonstrate that the observed wake characteristics can be well explained by intraspecific variability in flexural rigidity, thus demonstrating the importance of biomechanical traits in determining flow‐vegetation‐sediment interactions.