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Numerical modeling of the influence of tides on cross-shore sediment dynamics of dissipative beaches under moderate wave conditions
Continental Shelf Research ( IF 2.3 ) Pub Date : 2021-02-20 , DOI: 10.1016/j.csr.2021.104381
Viyaktha Hithaishi Hewageegana , Alberto Canestrelli

The influence of tides on cross-shore sediment dynamics of a longshore-uniform beach is studied by means of a 1D numerical model (XBeach). The model is modified to include longshore tidal currents induced by water level gradients. The effect of tides on cross-shore sediment dynamics is quantified by analyzing the change in suspended sediment concentration, sediment advection velocity, and sediment transport. The effect of tides is decoupled into its two main components, i.e., water level fluctuations and tidal currents. Water level fluctuations modulate wave orbital velocities, wave-averaged currents and sediment advection velocity, therefore affecting both resuspension of sediments and cross-shore sediment transport. Tidal currents favor tidally-averaged sediment resuspension due to the increase in applied shear stress on the bed. The effects of water level fluctuations and tidal currents on sediment dynamics vary in the cross-shore direction: tidal currents increase sediment resuspension in deeper water depth, while water level fluctuations control the changes observed in shallow waters. In shallow waters, tidal amplitude is a good indicator of the influence of longshore propagating tides on the cross-shore sediment dynamics of a uniform beach, while in deeper waters, tidal wavelength also plays an important role. The model predictions are able to capture the trends observed in field measurements.



中文翻译:

潮汐对中等波浪条件下耗散性海滩跨岸沉积物动力学影响的数值模拟

利用一维数值模型(XBeach)研究了潮汐对长海岸均匀海滩跨岸沉积物动力学的影响。对该模型进行了修改,以包括由水位梯度引起的近岸潮流。通过分析悬浮泥沙浓度,泥沙对流速度和泥沙输送的变化,可以量化潮汐对跨岸泥沙动力学的影响。潮汐的影响被分解成两个主要成分,即水位波动和潮流。水位波动会调节波浪轨道速度,波浪平均水流和沉积物平流速度,因此会影响沉积物的再悬浮和跨岸沉积物的运输。由于在河床上施加的切应力增加,潮汐流有利于潮汐平均沉积物的重悬。水位波动和潮汐流对沉积物动力学的影响在跨岸方向上有所不同:潮汐流在更深的水深处增加了沉积物的重悬,而水位波动控制着在浅水区观察到的变化。在浅水域,潮汐振幅是均匀分布的海滩对跨岸沉积物动力学影响的良好指标,而在较深水域,潮汐波长也起着重要作用。模型预测能够捕获现场测量中观察到的趋势。潮汐振幅很好地表明了沿岸传播的潮汐对均匀海滩跨岸沉积物动力学的影响,而在更深的水域中,潮汐波长也起着重要的作用。模型预测能够捕获现场测量中观察到的趋势。潮汐振幅很好地表明了沿岸传播的潮汐对均匀海滩跨岸沉积物动力学的影响,而在更深的水域中,潮汐波长也起着重要的作用。模型预测能够捕获现场测量中观察到的趋势。

更新日期:2021-02-24
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