Swash zone sediment transport, step dynamics and morphological response on a gravel beach
Swash zone sediment transport, step dynamics and morphological response on a gravel beach
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DOI：
10.1016/j.margeo.2010.03.005
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发表时间：
2010-08
期刊：
影响因子：
2.9
通讯作者：
G. Masselink;P. Russell;C. Blenkinsopp;Ian L Turner
中科院分区：
文献类型：
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作者：
G. Masselink;P. Russell;C. Blenkinsopp;Ian L Turner
最新的地形动态场数据来自英国的斯莱普顿沙滩(Slip Ton Sands)，这是一个细砾石海滩(D50=2-10 mm)，在一系列潮汐条件下，包括南向涌浪和东风波(Hs=0.5-1m；ts=4-8s；潮差=3-4m)，在10天内收集了数据。在现场期间，上滩在低陡度、涨落为主的潮汐条件下经历了淤积和护堤的形成(H/L和lt0.01)，在高陡度风浪主导的潮汐中经历了侵蚀(H/L>；0.01)。令人惊讶的是，潮间滩表现出相反的趋势，在涨潮条件下泥沙损失和风浪造成的泥沙体积增加，表明上层海滩的形态变化可以与总体泥沙收支脱钩。一种水下吸积特征(海滩阶地)在涨潮时生长并迁移到岸上，通常达到最大起伏约0.5米，然后随着潮汐下降向近海迁移时逐渐减弱，导致净形态变化很小。该阶梯在落潮时比涨潮时发育得更好，并通过其对水流和泥沙动力的控制，对护堤的发育产生了显著的影响。在所测量的条件下，上冲和反冲洗的冲刷流速通常都超过2ms−1。岸上平均流发生在上波浪区(40%淹没)，而下波浪区(40%淹没)以离岸平均流为特征。冲刷区的入渗损失从冲刷区的40%增加到上冲刷区的100%。最强的激流和最强的近海平均流出现在激流带和冲浪带之间的交界处(90-100%淹没)。
State-of-the-art morphodynamic field data were collected from Slapton Sands (UK), a fine-gravel beach (D50=2–10mm), over a 10-day period under a range of wave–tide conditions, comprising a mixture of southerly swell and easterly wind waves (Hs=0.5–1m; Ts=4–8s; tide range=3–4m). Over the field period, the upper beach experienced accretion and berm formation during tides with low steepness, swell-dominated wave conditions (H/L<0.01), and underwent erosion during tides dominated by high steepness wind waves (H/L>0.01). Surprisingly, the intertidal beach showed an opposite trend with sediment losses under swell conditions and an increase in sediment volume due to wind waves, and suggests that upper beach morphological change can be decoupled from the overall sediment budget. A submerged accretionary feature (the beach step) grew and migrated onshore on the rising tide, typically reaching a maximum relief of around 0.5m, then gradually decreased in prominence while migrating offshore as the tide fell, resulting in little net morphological change. The step was better developed during the falling tide than the rising tide and, through its control on the swash hydro- and sediment dynamics, the step had a significant effect on the development of the berm. Swash flow velocities under the conditions measured were often in excess of 2ms−1for both the uprush and the backwash. Onshore mean flows occurred in the upper swash region (<40% inundation), while the lower swash region (>40% inundation) was characterised by offshore mean flows. Swash infiltration losses in the swash zone increased from 40% in the lower swash region to 100% in the upper swash region. The most energetic swash flows and the strongest offshore mean flows occurred at the transition between swash zone and surf zone (90–100% inundation).