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1.
研究近海海域水流、悬沙运动规律，运用基于COHERENS发展的水动力悬沙模型COHERENS-SED,结合当地一般波浪条件，模拟了青岛近海悬浮泥沙输运情况，并验证及分析了水动力环境及悬沙输运的模拟结果。结果表明：在波流合作用下，近岸掀沙明显，大潮期间该海域近岸悬沙浓度值最高可达50mg／L。 相似文献
2.
根据2006年10月在崇明东滩潮间带和潮下带两个站位的大小潮水文泥沙观测资料和悬沙水样的室内粒度分析资料,对悬沙粒径的时空分布特征及其与流速等的关系进行了分析,并对再悬浮特点进行了探讨,结果表明,大小潮期间的悬沙颗粒组成较细,平均粒径的均值仅为6μm;大潮时的悬沙粒径略粗于小潮的,潮间带的略粗于潮下带的;由底床向上悬沙粒径趋于减小。悬沙粒径与流速、悬沙含量无明显的统计学关系,底质粒径、再悬浮强度和再悬浮泥沙粒径的空间变化以及浮泥的悬浮作用等是主要的影响因素。由于底质粒径的空间分布复杂,在东滩水域再悬浮具有明显的空间变化。在底质平均粒径大于60μm的粗颗粒沉积区,大小潮的再悬浮作用微小,底质以推移质运动为主。在底质平均粒径介于5~11μm的细颗粒沉积区上,悬沙级配与底质级配基本相同,该区域是再悬浮的主要发生源地;悬沙级配的变化过程揭示,再悬浮对底层悬沙的贡献率平均为8%~20%,大潮时的再悬浮强度是小潮的5~10倍,由底质再悬浮产生的悬沙在底部水层中的平均含量约为0.03~0.47 kg/m3。 相似文献
3.
Several important mechanisms for storm-induced entrainment of estuarine cohesive sediments are analyzed using field measurements collected in a moderately energetic estuary, central Long Island Sound, U.S.A. The sediment concentration and hydrographic data were obtained by an array of sensors mounted at 1 m above the bottom. The bottom sediment in the study site composed mostly of silt and silty sand. The study showed that the bottom shear stress, computed using a wave-current interaction model, increased significantly during the episodic wind events. A large resuspension event was triggered by a frontal passage when strong wind-driven currents augmented the tidal currents. The timing of storm waves with respect to the tidal phase also was a critical factor. Based on the changes of suspended sediment concentration, the bottom appeared to respond to the shear stress in two phases: the tidal resuspension and the storm-induced erosion. During each tidal cycle, entrainment was associated with resuspension of high water content, loosely consolidated material. During episodic events, a thin layer of more consolidated bed below the sediment-water interface was eroded by the enhanced bottom stress. 相似文献
4.
CHOIByung-Ho MUNJong-Yoon KOJin-Seok YUKJin-Hee 《中国海洋工程》2005,19(2):235-250
Described is an initial attempt to simulate the suspended sediment dynamics relating to tidal and wave forcing during summertime in June 1980 and August 1981 for the Yellow and East China Seas continental shelf. The cohesive/non-cohesive sediment resuspension and movement generated by the interaction between current and wave are modeled by use of ECOMSED and WAM Cycle 4. Model results are compared with observations in US-China Marine Sedimentation Dynamics Program performed for 1980-81 at off the Changiiang estuary. The main features of simulations show that suspended sediment concentrations during the summer decreased markedly offshore as observed during the simulation periods. As for some discrepancies for the mouth of the estuary with high river discharges, i.e., the Changjiang River, the model did not properly reproduce the over-mixing situation in the summer; thus distinct vertical concentration variation in this local region is not agreeable with observation. However, general dispersal patterns of suspended sediment movement seem to be agreeably reproduced for the nearshore shallow region. Some of the procedures of simulation and results are presented and discussed. 相似文献
5.
海洋动力作用下,河口海岸地区海床通常处于动态变化之中。作为地质环境的控制因素,海床沉积物侵蚀再悬浮过程的研究具有重要意义。为阐明胶州湾海域水动力条件对海床侵蚀再悬浮的作用,本文利用海底原位观测三脚架进行了现场观测。观测结果显示：通常条件下,潮流导致的最大海床剪应力可达0.35 N/m2,高于波浪引起的剪应力。涨潮期间,海床发生侵蚀;退潮期间,海床发生淤积。风速达到5 m/s时,波浪引起的剪应力近似等于流致剪应力。风速达到7 m/s时,有效波高为26 cm,波浪对海床侵蚀再悬浮过程起主要作用;此时也会导致海水浊度显著上升,高于通常条件下的2-8倍。分析表明：通常条件下,周期性海流影响海床侵蚀再悬浮过程;而大幅度沉积物再悬浮过程由偶发的波浪事件控制。针对胶州湾沉积物动力学机制的深入研究仍待进一步开展。 相似文献
6.
长江河口波-流共同作用下的全沙数值模拟 总被引：15，自引：1，他引：15
针对长江河口地形、水文、泥沙运动等复杂的特点,建立了波-流共同作用下的二维全沙及河床演变模型.在合理计算研究区域流场等的基础上,利用切应力概念确定悬沙扩散方程中的源函数;通过系列数值试验和实测资料的统计分析,在经典的泥沙临界起动速度中引入反映河床底质结构及固结程度的局地系数;选用由流速、盐度、含沙量浓度确定的泥沙颗粒絮凝沉降速度,从而提高长江口悬沙场数值模拟精度.在底沙输运计算中,提出一种较为合理确定有关参数的方法.通过洪、枯季大、中、小潮水文、泥沙资料和典型台风引起航槽冲淤变化的实测资料验证,表明该文提出的模型能较合理地反映长江河口流场、泥沙场及地形的演变. 相似文献
7.
基于遥感反演的莱州湾悬沙分布及其沉积动力分析 总被引：5，自引：3，他引：2
选用1986-2004年不同时期的LandsatTM/ETM+影像,利用2004年黄河口附近实测数据推导的表层悬浮泥沙浓度反演模型,结合水文气象资料、多年水深数据和极端天气数模结果,研究了莱州湾西南近岸海域表层悬浮泥沙分布特征,结果表明,受黄河丰枯水期的影响,莱州湾西南部海域悬浮泥沙高浓度区主要分布于黄河口附近海域和西南沿岸,其枯水期的覆盖范围一般大于丰水期的。受潮流高流速场控制,黄河口外悬沙浓度高值区与海底泥沙堆积区对应较好,泥沙主要来源于陆源输沙和泥沙再悬浮;在西南近岸浅海区悬沙浓度高值区主要形成于泥沙的再悬浮,在近岸出现轻微冲刷。风等其他海洋动力因素,一般情况下对悬浮泥沙扩散的程度和范围具有一定的影响作用,但悬沙受潮流场影响而形成的总体扩散趋势未发生改变;极端条件下,风暴潮流使莱州湾西南部近岸浅海区的悬浮泥沙浓度显著增加。 相似文献
8.
基于ADP-XR和OBS-3A的潮滩水文泥沙过程研究 以胶州湾北部红岛潮滩为例 总被引：2，自引：1，他引：2
于2004年8月17~24日在胶州湾北部红岛潮滩上用OBS-3A和ADP-XR观测了水深、浊度、水平和垂直流速、回声强度、波浪、盐度、水温等水文泥沙要素,同时采集了悬沙和底沙样品作粒度分析.结果和结论为:(1)潮流动力较弱,表层和近底层最大流速分别只有31和26cm/s;(2)弱潮流动力导致潮周期大部分时间的悬沙浓度小于30mg/dm3,但浅水阶段近底悬沙浓度为100~1000mg/dm3;浅水阶段的短暂高悬浮泥沙浓度和其余长淹没时段的低悬沙浓度共同构成悬沙浓度的“U”形潮周期过程线;(3)悬沙浓度的垂直成层分布主要发生在潮周期的深水阶段和平静天气;(4)由于潮流弱和风浪的干扰,悬沙浓度未呈现大小潮周期的变化规律;(5)水体盐度为23.6~29.5;(6)淹没期的温度(21.4~28.6℃)比出露期的(19.3~30.9℃)稳定,温度极高值出现在午后出露期,而极低值出现在凌晨出露期;(7)“浅水效应”是弱动力潮滩泥沙运动的重要特点. 相似文献
9.
1Introduction The sediment dynamics of intertidal flats in-volves erosion, transport, and settling processes. A-mong these, the mechanisms of sediment transportare a key question. Progress has been made in awide range of associated areas, including sedime… 相似文献
10.
观测红树林潮滩在波浪和潮流作用下的近底层垂向剖面悬沙浓度变化过程, 对理解海岸带植被的消能促淤机制和滨海湿地生态修复工程有着重要作用。本文以北部湾七星岛岛尾桐花树红树林潮滩为例, 基于剖面流速仪HR、声学多普勒单点流速仪ADV、浪潮仪T-wave及剖面浊度仪ASM, 获取了研究区域2019年夏季大潮连续3天的水文数据, 同时结合桐花树典型植株实测参数, 分析了潮周期内红树林潮滩近底层垂向剖面悬沙响应波浪、潮流作用及桐花树空间结构的运动过程。结果表明: 1) 桐花树潮滩近底层悬沙浓度和悬沙通量具有涨潮明显大于落潮的潮汐不对称现象, 剖面垂向高悬沙浓度区域在涨潮初期—涨急由距底部0.1~0.37m转变为距底部0.5~0.67m, 落急—落潮末期则由上部转变为下部; 2) 潮周期内悬沙起动和再悬浮阶段发生在以波浪作用主导的涨潮初期和落潮末期, 平流和沉降发生在以潮流作用为主的涨急至落急整个阶段; 3) 涨潮阶段桐花树冠层的茂密枝叶通过减缓流速拦截多于冠层上部40%以上的悬沙, 落潮水体则挟沙自陆向海经过桐花树群落, 使得悬沙浓度下降超过71%。该不对称涨、落潮动力沉积机制有利于悬沙向岸输运, 促进潮滩扩张过程。 相似文献
11.
江苏大丰潮滩悬沙级配特征及其动力响应 总被引：1，自引：5，他引：1
根据2002和2003年夏季在江苏大丰潮滩的现场观测资料,详细分析了悬沙级配的时空分布特征、影响因素及其对再悬浮、沉降和流速的响应.研究结果表明,悬沙颗粒较细,以粉砂为主,悬沙级配在潮周期内的变化模式有两种类型:一是稳定型,悬沙级配的时空(垂向和平面)变化很小;二是双峰型,悬沙级配的时空变化显著,粗细峰高度不断变化.再悬浮、沉降、涨潮时输入潮滩的悬沙和底质级配是影响悬沙级配的重要因子.再悬浮使粗颗粒悬沙的含量增加,悬沙与底质级配不断接近,沉降对悬沙级配的影响与再悬浮相反.再悬浮发生时悬沙级配对流速有明显响应.在没有再悬浮和沉降影响的情况下,潮滩不同部位、不同时间的悬沙级配趋于稳定和相同,对这种状态下的悬沙级配可称为背景悬沙级配,大丰潮滩背景悬沙级配的平均粒径为7μm. 相似文献
12.
Field measurements were conducted in Mont-Saint-Michel Bay, a megatidal embayment (spring tidal range of 15 m), in order to monitor, over the course of a tidal cycle, sediment transport variability due to waves and tides on the upper part of a tidal flat characterised by shallow water depths. Sensors used to measure currents, water depth and turbidity were installed just above the bed (0.04 m). Two experiments were conducted under contrasting hydrodynamic conditions. The results highlight wave activity over the tidal flat even though observed wind waves were largely dissipated due to the very shallow water depths. Very high suspended sediment concentrations (up to 6 kg/m3) were recorded in the presence of wave activity at the beginning of the local flood, when significant sediment transport occurred, up to 7 times as much as under conditions of no wave activity. This influence may be attributed to the direct action of waves on bed sediments, to wave-induced liquefaction, and to the erosive action of waves on tidal channel banks. The sediment composition, comprising a clay fraction of 2-5%, may also enhance sediment transport by reducing critical shear stress through the sand lubrication effect. The results also show that antecedent meteorological conditions play an important role in suspended sediment transport on the tidal flat. Total sediment flux directions show a net transport towards the inner part of the bay that contributes to deposition over the adjacent salt marshes, and this tendency also prevails during strong wave conditions. Such sediment transport is characterised by significant variability over the course of the tidal cycle. During fair and moderate weather conditions, 83% and 71% of the total flux was observed, respectively, over only 11% and 28% of the duration of the local tidal cycle and with water depths between 0.04 and 0.3 m. These results suggest that in order to improve our understanding of sediment budgets in this type of coastal environment, it is essential to record data just at the beginning and at the end of tidal submergence close to the bed. 相似文献
13.
The Bay of Banten is an example of a shallow-water reef environment adjacent to an eroding delta system, where corals survive in turbid conditions. This study investigated the hydrodynamic controls over residual fluxes of terrigenous sediment in the bay. Observations of wind, waves, currents and suspended sediment concentrations in 1998 and 1999 revealed contrasting dynamic turbidity conditions influenced by tides, monsoon-driven flows and locally generated waves. The most sediment-rich suspensions originate from the shallow coastal margin of an inactive delta, where waves resuspend sediment and small creeks discharge freshwater and sediment. Because of coupling between monsoonal wind, throughflow in the bay and wave height, when wave-induced resuspension peaks seasonally during the northwest monsoon, an eastward throughflow prevents the nearshore reefs in the bay from being directly exposed to turbid water masses generated in the eroding delta. In inshore waters, tidal asymmetry and the spatial variation of current amplitudes cause residual sediment transport, largely depending on the availability of erodible sediment. In the center of the bay, where there is a patch reef complex, the tidal and subtidal currents are weak and therefore here there is a zone where sediment accumulates. 相似文献
14.
Sediment transport in the Hangzhou Bay is extremely complicated due to its bathymetry and hydrodynamic conditions. The ECOMSED model is employed to simulate three-dimensional (3-D) cohesive sediment transport in Hangzhou Bay. Dynamical factors such as Coriolis force, tides, salinity, river discharges, and waves are considered in the model. The wave parameters, including the significant wave height, period, and direction, are calculated with the SWAN model. The Grant-Madsen model is introduced for the bed shear stress due to the combined effect of waves and currents. The formulation of bed shear stress used to calculate the sink/source terms is modified based on previous research that sufficiently validated the formulation with measurement data. The integrated model of the above-mentioned models is applied to simulate sediment transport in Hangzhou Bay. The results of the simulation agree well with field observations concerning the distribution of suspended sediment, indicating that the sediments are remarkably suspended in Hangzhou Bay under the action of waves and currents. 相似文献
15.
实施人工岬角和海滩养护的软硬措施相结合的方法是探索解决海滩侵蚀问题的新举措之一。基于验证良好的水动力模型建立了泥沙输运和海床演变模型,对秦皇岛市新开河口至南山岸线海滩经整治修复工程实施后的泥沙输运和海床演变规律进行模拟分析。结果表明:大潮与常浪耦合作用下,研究区域周围海域流速整体上落急时刻大于涨急时刻,沙坝掩护水域的流速较弱,波浪在沙坝处增强并在沙坝后破碎并减弱;在沙坝处出现高悬沙浓度区域,悬沙浓度分布主要由底床切应力控制,部分受水动力影响。大潮与强浪耦合作用下,在沙坝处出现远大于常浪时的增强水流(波生流),方向与强浪向一致,波浪在沙坝处已破碎且沙坝对强浪的削减效率大于常浪;与常浪作用下不同,悬沙浓度场在强浪作用下沙坝处没有出现明显的高浓度区域。波流耦合作用下,人工岬角单独存在时护岸效果有限,工程实施后在人工岬角和人工沙坝的配合下,沙坝处侵蚀而沙坝后侧掩护区域淤积,沙坝起到了有效养护海滩的作用。 相似文献
16.
Franz E. Anderson 《Marine Geology》1973,14(2):101-116
In order to examine sedimentary processes acting on tidal flats, eighteen foot valves were “plumbed” into a small tidal cove in southern New Hampshire. Transport of suspended sediment was determined by comparing concentrations (determined by filtering) at 15 and 30 cm above the tidal flats throughout a tidal cycle. In general, sediment resuspension occurs more readily on the flood tide than the ebb. The concentration of suspended sediment follows the water mass distribution and is affected to a lesser degree by tidal currents and small amplitude waves. Deposition occurs during slack water shortly after high tide primarily in the bottom regime (15 cm); it is probably related to coarser particle sedimentation. The water mass distribution was not a simple rise and fall perpendicular to the bottom contours, but rather followed a slow clockwise gyre. The net effect on the suspended sediments was to impart a “longshore” component of drift to the suspended load during the tidal cycle. 相似文献
17.
Owing to lack of observational data and accurate definition,it is difficult to distinguish the Kuroshio intrusion water from the Pacific Ocean into the South China Sea(SCS).By using a passive tracer to identify the Kuroshio water based on an observation-validated three-dimensional numerical model MITgcm,the spatio-temporal variation of the Kuroshio intrusion water into the SCS has been investigated.Our result shows the Kuroshio intrusion is of distinct seasonal variation in both horizontal and vertical directions.In winter,the intruding Kuroshio water reaches the farthest,almost occupying the area from 18°N to 23°N and 114°E to 121°E,with a small branch flowing towards the Taiwan Strait.The intrusion region of the Kuroshio water decreases with depth gradually.However,in summer,the Kuroshio water is confined to the east of 118°E without any branch reaching the Taiwan Strait;meanwhile the intrusion region of the Kuroshio water increases from the surface to the depth about 205 m,then it decreases with depth.The estimated annual mean of Kuroshio Intrusion Transport(KIT) via the Luzon Strait is westward to the SCS in an amount of –3.86×106 m3/s,which is larger than the annual mean of Luzon Strait Transport(LST) of –3.15×106 m3/s.The KIT above 250 m accounts for 60%–80% of the LST throughout the entire water column.By analyzing interannual variation of the Kuroshio intrusion from the year 2003 to 2012,we find that the Kuroshio branch flowing into the Taiwan Strait is the weaker in winter of La Ni?a years than those in El Ni?o and normal years,which may be attributed to the wind stress curl off the southeast China then.Furthermore,the KIT correlates the Ni?o 3.4 index from 2003 to 2012 with a correlation coefficient of 0.41,which is lower than that of the LST with the Ni?o 3.4 index,i.e.,0.78. 相似文献
18.
Fine sediment resuspension dynamics in a large semi-enclosed bay 总被引：3，自引：0，他引：3
A field study was conducted to investigate fine sediment resuspension dynamics in Moreton Bay, a large semi-enclosed bay situated in South East Queensland, Australia. One S4ADW current meter and three OBS sensors were used to collect the field data on tides, mean currents, waves and suspended sediment concentrations in a mean water depth of 6.1 m for about 3 weeks. Two small cleaning units were specially designed to automatically clean the OBS sensors several times every hour to avoid biological growth on the OBS sensors. Based on the collected field data, the main driving force for fine sediment resuspension is found to be the storm wind-waves generated locally in the Bay, not the tidal current or penetrated ocean swell. The critical wind-wave orbital velocity for sediment resuspension was determined to be Urms=7 cm/s and the critical bed shear stress τcr=0.083–0.095 Pa at this study site. 相似文献
19.
Very small waves and associated sediment resuspension on an estuarine intertidal flat 总被引：2，自引：0，他引：2
Field data from a microtidal estuarine intertidal flat (Tamaki estuary, New Zealand) are used to analyse very small waves (height <10 cm; period 1.0–1.8 s) and associated sediment resuspension under light winds. Mean spectral period at the bed varied over the tidal cycle, driven by changes in surface-wave spectrum and depth-attenuation of orbital motions. Wave-orbital currents exceeded 30 cm/s, disturbing the fine-sand (100–200 μm) matrix of the seabed and resulting in the release of fine silt (particle size <20 μm) at concentrations >120 mg/L. Resuspension was initiated when ∼40% of the maximum zero-downcrossing orbital speeds in a burst exceeded the critical speed for initiation of sediment motion. Sediment concentrations were highest around low tide, when waves were smaller compared to high tide because of a reduced fetch but depth-attenuation of orbital motions was less because the water was shallower. Wave period exerted a control on sediment resuspension through the wave friction factor. There was a hysteresis in the wave Reynolds number such that it was greater on the ebbing tide compared to on the flooding tide: since it did not exceed 3 × 105 the bed was hydraulically smooth, and the wave friction factor therefore is inversely proportional to wave period. Hence, the tidal-cycle hysteresis in wave Reynolds number translated into a smaller wave friction factor on the ebbing tide, and accounting for this caused the ebb and flood sediment concentration data to collapse onto one curve when plotted against wave-induced skin friction. A simple model is presented to evaluate the relative contribution to sediment resuspension of waves associated with weak and strong winds. At the base of the flat (waves competent to resuspend sediment for 5% of the inundation time), waves associated with stronger, infrequent winds dominate resuspension. At the top of the flat (waves competent to resuspend sediment for 30% of the inundation time), waves associated with lighter, frequent winds dominate resuspension. Moderate winds – neither the strongest nor most frequently occurring – dominate resuspension integrated across the profile. The mass of sediment resuspended by waves is greatest towards the top of the flat: shoreward of this, resuspension is smaller because of wave dissipation; seaward of this, resuspension is smaller because of greater depth-attenuation of orbital motions. The location of maximum sediment mass resuspended by waves and the location of maximum duration of resuspension are not necessarily the same. 相似文献