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1.
The fishery harbor of Karaburun coastal village is located at the south west coast of the Black Sea. The significant waves coming from north eastern direction cause considerable rate of sediment transport along 4 km sandy beach towards the fishery harbor in the region. The resulting sediment deposition near and inside the harbor entrance prevents the boat traffic and cause a vital problem for the harbor operations. In order to determine the level and reasons of the sediment transport, the long-term observations of shoreline changes, the long-term statistical analysis of wind and wave characteristics in the region, and sediment properties have been performed. The data obtained from observations, measurements and analysis were discussed. The long-term statistics of deep water significant wave heights for each direction was discussed by comparing the results obtained from different data sources and methods. For shoreline evolution, the numerical study using one-line model was applied to describe the shoreline changes with respect to probable wave conditions. Initial shoreline was obtained from the digitized image in 1996 since there was no previous shoreline measurement of the site. The results were compared using the techniques of remote sensing obtained from sequent images using IKONOS and IRS1C/D satellites. 相似文献
2.
A Comparison of Near-Bed Acoustic Backscatter and Laser Diffraction Measurements of Suspended Sediments 总被引：2，自引：0，他引：2
As part of the U.S. Office of Naval Research (ONR, Arlington, VA) mine burial program, an experiment was conducted off the pier at Santa Cruz, CA, to measure the near-bed suspended sediment reference concentration under waves and currents. Two tripods were deployed to carry out the measurements; one consisting mainly of acoustical instrumentation and the other solely of optical instruments. The tripods were located within 15 m of one another on a sandy bed and measurements of the suspended sediment were made using acoustics and optics. Although the experiment was not primarily designed to conduct an intercomparison of acoustical and optical measurements, it was considered interesting to take advantage of the situation and to examine if these two techniques gave comparable results. In particular, measurements of particle size and concentration, obtained using a triple frequency acoustic backscatter system (ABS) have been compared with the commercially available laser miniature scattering and transmissometry instrument (MSCAT). It was found that the mean grain size estimated by the two methods was consistent; however, in contrast, the concentration time series showed differences, both in magnitude and form. 相似文献
3.
A previously published wave-averaged version of Bailard's sediment transport formulation, intended for use in a numerical model of shelf sand transport, is compared against available field observations from literature. The objective was to test the performance of the transport relation over the wide range of hydrodynamical conditions that can occur at sea. A modified data analysis method was used to assess the reliability of the field observations. The modification consists of a method to cluster the data into classes to enable statistical analysis. The sediment transport formulation is part of the classification method. The method is in principle also suitable to reduce the size of data sets of non-cohesive sediment transport obtained with modern electronic equipment. The results show that the quality of the published field observations is fair, and that the wave-averaged Bailard formulation performs well for low and medium transport regimes in both currents and waves. For those conditions, it yields a slight overprediction of the transports, and a nearly uniform behaviour as a function of the conditions. The formulation underestimates transport rates for very high flow velocities in absence of waves, which is in agreement with earlier findings. The present version of Bailard's wave averaged sediment transport formulation is suitable for computing the local transport rates of fine to coarse sand on continental shelves in conditions ranging from small currents to moderate currents combined with non-breaking waves. 相似文献
4.
Dajun Tang Briggs K.B. Williams K.L. Jackson D.R. Thorsos E.I. Percival D.B. 《Oceanic Engineering, IEEE Journal of》2002,27(3):546-560
As part of the effort to characterize the acoustic environment during the high frequency sediment acoustics experiment (SAX99), fine-scale variability of sediment density was measured by an in situ technique and by core analysis. The in situ measurement was accomplished by a newly developed instrument that measures sediment conductivity. The conductivity measurements were conducted on a three-dimensional (3-D) grid, hence providing a set of data suited for assessing sediment spatial variability. A 3-D sediment porosity matrix is obtained from the conductivity data through an empirical relationship (Archie's Law). From the porosity matrix, sediment bulk density is estimated from known average grain density. A number of cores were taken at the SAX99 site, and density variations were measured using laboratory techniques. The power spectra were estimated from both techniques and were found to be appropriately fit by a power-law. The exponents of the horizontal one-dimensional (1-D) power-law spectra have a depth-dependence and range from 1.72 to 2.41. The vertical 1-D spectra have the same form, but with an exponent of 2.2. It was found that most of the density variability is within the top 5 mm of the sediment, which suggests that sediment volume variability will not have major impact on acoustic scattering when the sound frequency is below 100 kHz. At higher frequencies, however, sediment volume variability is likely to play an important role in sound scattering. 相似文献
5.
一、序言 从遙感信息中提取海洋信息是海洋遙感应用的核心问题。 从遙感数据提取海洋数据,现在已经有很多方法与模型。各种方法都有它们的长处和短处。从目前发表的遙感文章来看,大多还是使用数理统计模型。它的优点是方法比较简单,且比较精确。缺点是有很大的局限性,它的结果只有在特定的海区、特定的大气条件和飞行 相似文献
6.
B. J. Lees 《Geo-Marine Letters》1981,1(3-4):249-254
A method is described to calculate the relationship (β) between the eddy diffusivity of suspended particles and the eddy viscosity
of the fluid. The data were obtained while making suspended sediment concentration measurements near the seabed on the British
continental shelf. β was calculated for 0.50 size fractions and varies inversely with the suspended sediment concentration.
The values were used successfully to calculate suspended sediment transport rates for separate sand fractions through a spring
tidal cycle. Finally, specific values of β are suggested for varying concentrations of sand at a reference height of 100 cm
above the seabed. 相似文献
7.
声学方法监测悬浮物浓度的定标技术研究 总被引：2，自引：0，他引：2
海洋中特别是河口海岸中存在着大量的悬浮物，其中，包含有内陆河流夹带的大量泥沙、海洋内浮游生物及残骸，以及大陆倾倒的大量废水废渣，造成对海洋的污染。研究悬浮物随深度剖面的变化关系，即它的时空特性，将给河口和港湾的疏浚、泥沙综合治理、沿岸工程建设、环境污染防止等方面提供可靠的理论依据和直观方便的监测手段。所以，对悬浮物浓度的定标的研究有着十分重要的现实意义。 相似文献
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ADCP measurements of suspended sediment flux at the entrance to Jiaozhou Bay, western Yellow Sea 总被引：1，自引：1，他引：0
The purpose of the present contribution is to explore the technique to use Acoustic Doppler Current Pro- filers （ADCPs） for suspended sediment flux measurements, which may be applied to coastal embayment environments such as estuaries and tidal inlets for sediment exchange and budget studies. Based on tidal cycle measurements from the entrance of ]iaozhou Bay, Shandong Peninsula, eastern China, statistical rela- tionships between the suspended sediment concentration （SSC） and ADCP echo intensity output are estab- lished. Echo intensity data obtained during an ADCP survey along two cross-sections during a spring tidal phase were transformed into SSC data. The ADCP current velocity and SSC data were then used to calculate the flux of fine-grained sediment. The results show that net sediment transport at the entrance is directed towards the open sea, with an order of magnitude of 103 t per spring tidal cycle; hence, although Jiaozhou Bay is a low SSC environment, the tidally induced suspended sediment transport can be intense. 相似文献
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11.
渤海海峡沉积物输运的参数化计算 总被引：1，自引：1，他引：0
本文以2018年冬季渤海海峡两个站位的定点连续观测数据为基础，使用一维参数化方案，计算了观测站位底边界层内的水平悬浮物输运通量以及推移质输运量。在参数化方案中，简化的一维对流扩散方程被用于计算底边界层内的垂向悬浮物浓度。为了验证参数化方案的可靠性，本文基于观测数据对比了两种底剪切应力计算模型、四种临界起动剪切应力计算方法和两种一维对流扩散方程解法。对比结果表明:(1)不同模型计算的底剪切应力结果相近；(2)临界起动剪切应力受到颗粒间黏性作用的影响；(3)一维对流扩散方程的求解过程需要考虑沉积物浓度的分层效应和不同粒级颗粒临界起动剪切应力的差异。基于上述对比结果确定的最优参数化方案，进一步计算了观测站位的沉积物输运量:(1)在有再悬浮的时段，距底5 m内的水平悬浮物通量占全水深悬浮物通量的比例(T01站约为21%，T02站约为17%)显著高于相同层位水通量的占比；(2)依据参数化方案估算的冬季平均的悬浮物通量比忽略底边界层悬浮物浓度垂向变化的传统方法结果高约16%；(3)推移质输运量比悬移质输运量约低两个数量级。 相似文献
12.
The 25-h measurements of current speed, flow direction, water depth, suspended sediment concentration and salinity were carried out at six anchored stations in the study area during spring and neap tides in winter of 1987 and summer of 1989. Caculations and analyses of the data obtained show that large amounts of suspended sediments are moved back and forth under the action of tidal current, and the net transport of sediment is small, with its predominance upstream in winter and downstream in summer. These calculations and analyses also suggest that the advective transport of sediment is dominant, while the vertical gravitational circulation of the suspended sediment comes next. Meantime, it is indicated that tidal currents play a major role in the suspended sediment transport, and residual flows have effect on the net transport of the suspended sediment, which is more remarkable during neap tide than during spring tide. 相似文献
13.
David Hurther Peter D. Thorne Mickaël Bricault Ulrich Lemmin Jean-Marc Barnoud 《Coastal Engineering》2011
The use of acoustics to measure sediment transport boundary layer processes has gained increasing acceptance over the past two decades. This has occurred through the development of increasingly sophisticated measuring systems and theoretical developments, which have enabled flow and suspended sediment parameters to be obtained from acoustic data with a high degree of accuracy. Until relatively recently, separate acoustic systems were used to measure flow and suspended sediment concentration. Over the past few years, however, the technology has become sufficiently advanced so that flow and sediment measurements can be integrated into a single system. This integration provides, quasi-instantaneous, non-intrusive, co-located, high temporal-spatial resolution measurements of benthic flow and sediment processes. Here the development of such an instrument, the Acoustic Concentration and Velocity Profiler (ACVP) is described. The theory underpinning its application is outlined, new approaches to velocity de-aliasing and suspended sediment inversion instabilities using multi-frequency capabilities are presented and the application of the system to sediment transport processes over a sandy ripple bed is illustrated. The observations clearly show the value of such instrumentation for studying the dynamical interaction between the bed, the flow and the sediments at and within the bottom boundary layer. 相似文献
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Chapman N.R. Stinson K. Levy S. Cabrera J. Oldenburg D.W. 《Oceanic Engineering, IEEE Journal of》1988,13(4):215-221
A method has been presented for estimating the elastic properties of sea-floor sediment by inverting the amplitude-range information of precritical reflection data. The method was tested using synthetic data for reflection from a half-space sediment model and the estimates values for the P - and S -wave speeds and the density were in good agreement with the geoacoustic model parameters. The synthetic data were also used to determine the sensitivity of the method to interference from reflections from subbottom layers. In most practical cases the interference is not likely to be a problem for precritical reflection data. The method was then applied to measurements of seafloor reflection obtained in an experiment carried out off the west coast of Canada. The estimated values of the elastic properties of the topmost sediment layer were consistent with values available from the literature, and with estimates from other experiments carried out in the same region 相似文献
16.
《Coastal Engineering》2004,51(10):1021-1049
A numerical process-based model to forecast beach profile morphodynamics has been developed. In the present paper, an analysis of various modelling approaches and key parametrizations involved in the estimation of the wave-driven current and the suspended sediment concentration is carried out.Several resolution techniques for the 1DV horizontal (i.e., in the x-direction perpendicular to coastline) momentum equation governing the Mean Horizontal Velocity (MHV) are analysed. In the first kind of techniques, the mean horizontal velocity is computed from the momentum equation, whereas the Mean Water Level (MWL) is computed using a parametrization of the depth-averaged momentum equation. Two boundary or integral conditions are thus needed. In the second kind, both mean horizontal velocity and mean water level gradient in the x-direction are the unknowns of the momentum equation, thus, three boundary or integral conditions are needed. Various additional conditions are discussed. We show that using a technique of the first kind is equivalent to imposing the difference between the surface and the bottom shear stresses in the 1D vertical equation. Both techniques lead to results that are in good agreement with the Delta Flume experimental data, provided the Stokes drift flow discharge is imposed as an additional condition. The influence of the breaking roller model and of the turbulent viscosity parametrization are also analysed.Suspended sediment transport by the mean current and wave-induced bedload transport are taken into account in the sediment flux. Three turbulent diffusivity parametrizations are compared for suspended sediment concentration estimations. A linear profile for the turbulent diffusivity taking into account the wave bottom shear stress and the surface wave breaking turbulence production is shown to give the best results. Using experimental data, we put forward the poor estimation of the bottom sediment concentration given by the three implemented parametrizations. We thus propose a new parametrization relying on a Shields parameter based on the breaking roller induced surface shear stress. Using this new parametrization, the bottom profile used in the tests keeps its two bars which disappear otherwise. However, the morphodynamical model still overestimates the bars offshore motion, a bias already observed in other models. 相似文献
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INTRODUCTIONA~q~tityofmudsandSandsbIDughtbyinfluentriverssUSpendin~talseawater.ThemudsandSands,affectedbythetidesandc~ts,areconstantlymoving,tranSportinganddealting,andcancauseseriousinfluencesonharhars,channelsandwaterconservancies,coaStalandOffshae... 相似文献
19.
以废黄河三角洲表层粒度分析数据为基础,探讨了对数比转换和kriging插值相结合方法在沉积物粒级组分空间预测和底质类型制图中的应用。结果表明,基于沉积物粒级组分原始数据的kriging预测方法难以保证各组分预测结果的非负和定和要求,因而预测结果的可信度低;而对数比转换kriging方法不但满足非负和定和要求,而且还有着更优的组分预测结果和较高的底质类型制图精度。新方法对于开展定量化的沉积物粒级组分预测和底质类型制图具有参考价值。 相似文献
20.
In order to study the mechanism of flow-sediment movement, it is essential to obtain measured data of water hydrodynamic and sediment concentration process with high spatial and temporal resolution in the bottom boundary layer (BBL). Field observations were carried out in the northwest Caofeidian sea area in the Bohai Bay. Near 2 m isobath (under the lowest tidal level), a tripod system was installed with AWAC (Acoustic Wave And Current), ADCP (Acoustic Doppler Current Profilers), OBS-3A (Optical Backscatter Point Sensor), ADV (Acoustic Doppler Velocimeters), etc. The accurate measurement of the bottom boundary layer during a single tidal period was carried out, together with a long-term sediment concentration measurement under different hydrological conditions. All the measured data were used to analyze the characteristics of wave-current-sediment movement and the BBL. Analysis was performed on flow structure, shear stress, roughness, eddy viscosity and other parameters of the BBL. Two major findings were made. Firstly, from the measured data, the three-layer distribution model of the velocity profiles and eddy viscosities in the wave-current BBL are proposed in the observed sea area; secondly, the sediment movement is related closely to wind-waves in the muddy coast area where sediment is clayey silt: 1) The observed suspended sediment concentration under light wind conditions is very low, with the peak value generally smaller than 0.1 kg/m3 and the average value being 0.03 kg/m3; 2) The sediment concentration increases continuously under the gales over 6-7 in Beaufort scale, under a sustained wind action. The measured peak sediment concentration at 0.4 m above the seabed is 0.15-0.32 kg/m3, and the average sediment concentration during wind-wave action is 0.08-0.18 kg/m3, which is about 3-6 times the value under light wind conditions. The critical wave height signaling remarkable changes of sediment concentration is 0.5 m. The results show that the suspended load sediment concentration is mainly influenced by wave-induced sediment suspension. 相似文献