Bedform contributions to cross-shore sediment transport on a dissipative beach
Bedform contributions to cross-shore sediment transport on a dissipative beach
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河床形态对耗散海滩跨岸沉积物迁移的贡献
DOI：
10.1016/j.coastaleng.2015.01.007
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发表时间：
2015
影响因子：
4.4
通讯作者：
Miles J
中科院分区：
文献类型：
--
作者：
Miles J
在英国Perranporth的耗散性沙质海滩潮间带(D50=40.26 mm，坡度1/80)进行了水动力、悬移质输沙率和床面输沙率的现场测量。部署了12个潮汐的压力传感器、声学多普勒测速仪、光学后向散射传感器和声波沙纹剖面仪，测量的波高从0.5到2.2米，水深从1到6米，海流强度高达0.4米/S。数据根据海浪带宽度(Xs)归一化的离岸距离(X)进行分析，并横跨该地区0.4 cm/xs；；3.记录了高达30 cm的平台高度和0.5至2.7米的波长。在断点附近观察到了最大波长。床型分为亚轨型、涡波型。台状迁移主要是陆上定向的，并与正(陆上)波偏斜相关。仅在断点附近，通过浅水区的迁徙速度就增加到最大1.5厘米/分钟(x/xs=10.8)。泥沙输移的底形组分一般为岸上方向，最大值为断点的岸边(0.021 kg/m/S)。点位测量表明，河床以上25 cm处的跨岸悬沙输移以平均分量为主，近岸方向的最大输沙量为x/xs=100.5。对陆上传输的贡献仅由入射波(重力带)分量作出。总悬浮泥沙输移以近海方向为主，中浪带最大(−为0.16万kg/m/S)。内至中冲浪带(x/xs)和外浅滩带(x/xs)的底泥输移以深度综合悬沙输运为主。滩涂控制的河床输运对总绝对输运的贡献率高达100%，并广泛出现在断裂点区域(0.5x/xs)(1.5)。然而，跨岸的空间平均表明，更现实的河床对输运的贡献高达15%，最大值在x/xs=100.9时。这一耗散海滩实验的结果与以前在中等海滩、陡峭海滩和近海沙洲上的发现大体一致。
Field measurements of hydrodynamics, suspended sediment transport rates and bedform sediment transport rates were made in the intertidal section of a dissipative sandy beach (D50 = 0.26 mm, slope = 1/80) at Perranporth (UK). Pressure transducers, acoustic Doppler velocimeters, optical backscatter sensors and an acoustic sand ripple profiler were deployed for 12 tides, measuring in a range of wave heights from 0.5 to 2.2 m, water depths from 1 to 6 m, and in current strengths up to 0.4 m/s. Data were analysed in terms of the distance to shore (x) normalised by the surf zone width (xs), and spanned the region 0.4 < x/xs < 3. Bedform heights up to 30 cm and wavelengths 0.5 to 2.7 m were recorded. Maximum wavelengths were observed just shoreward of the breakpoint. Bedforms were classified as sub-orbital, vortex ripples. Bedform migration was mostly onshore directed, and correlated with positive (onshore) wave skewness. Migration rates increased through the shoaling zone to a maximum of 1.5 cm/min just shoreward of the breakpoint (x/xs = 0.8). The bedform component of sediment transport was generally onshore directed, and maximum just shoreward of the breakpoint (0.021 kg/m/s). Point measurements showed that the cross-shore suspended sediment transport 25 cm above the bed was dominated by the mean component, with an offshore directed maximum at x/xs = 0.5. Contributions to onshore transport were only made by the incident wave (gravity band) component. The total depth integrated suspended sediment transport was offshore directed and maximum in the mid surf zone (− 0.16 kg/m/s). The depth integrated suspended sediment transport dominated over the bedform sediment transport in the inner to mid surf zone (x/xs < 0.5) and in the outer shoaling zone (x/xs > 1.5). The fractional contribution of the shoreward directed bedform transport to the total absolute transport was up to 100%, and occurred broadly in the region of the breakpoint (0.5 < x/xs < 1.5). However, spatial averaging in the cross-shore indicated that a more realistic bedform contribution was up to 15% of the transport, with a maximum at x/xs = 0.9. Results from this dissipative beach experiment generally agree with previous findings on intermediate beaches, steep beaches, and offshore sandbars.
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DOI：
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DOI：
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发表时间：
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