Observations of gravel beach dynamics during high energy wave conditions using a laser scanner
Observations of gravel beach dynamics during high energy wave conditions using a laser scanner
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DOI：
10.1016/j.geomorph.2014.08.019
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发表时间：
2015-01-01
期刊：
影响因子：
3.9
通讯作者：
Davidson, M. A.
中科院分区：
文献类型：
--
作者：
Almeida, L. P.;Masselink, G.;Davidson, M. A.
在纯砾石海滩（英格兰康沃尔郡Loe Bar）的涨潮极限处部署了一台2D激光扫描仪，以测量高能波浪事件期间的高频（2.5 Hz）冲刷流体动力学和地形变化。通过激光扫描仪进行的测量进行了校正，以补偿找平和定向误差，并应用方差阈值将海滩地形与水运动分离开来。利用激光测量方法，通过计算冲刷峰值超过2% （R-2%）、冲刷速度偏度（）、冲刷光谱和累积地形变化等参数，表征了一个潮汐周期内的冲刷流体力学和形态变化。结果表明，在潮汐周期中，尽管净形态变化较小，但泥沙运动明显。在不同的潮汐阶段，发现了明显的不对称形态响应：涨潮以吸积为主，落潮以侵蚀为主。控制这种不对称形态响应的主要因素是阶跃迁移，阶跃迁移根据潮相的不同，控制了波浪的破碎点，从而控制了主要的泥沙输运方向。涨潮时，台阶发育降低了岸面坡度，降低了坡面能量；退潮时，台阶再活化使岸面坡度和坡面能量增加。(C) 2014年Elsevier B.V.出版
A 2D laser-scanner was deployed at the high tide runup limit of a pure gravel beach (Loe Bar, Cornwall, England) to measure high-frequency (2.5 Hz) swash hydrodynamics and topographic changes during an energetic wave event. Measurements performed with the laser-scanner were corrected to compensate for levelling and orientation errors, and a variance threshold was applied to separate the beach topography from the water motions. Laser measurements were used to characterise the swash hydrodynamics and morphological changes during one tidal cycle through the calculation of several parameters, such as the 2% exceedence of the runup maxima (R-2%), swash flow velocity skewness (), runup spectra and cumulative topographic changes. Results indicate that despite the small net morphological changes over the tide cycle, significant sediment mobilization occurs. A clear asymmetrical morphological response was found during the different tidal phases: the rising tide is dominated by accretion whilst the falling tide is dominated by erosion. The main factor controlling this asymmetrical morphological response is the step migration that, depending on the tide phase, controls the wave breaking point and consequently the dominant sediment transport direction. During the rising tide, step development decreases the shoreface slope and reduces the runup energy, whilst during the falling tide the step remobilization increases the shoreface slope and energy on the runup. (C) 2014 Published by Elsevier B.V.