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1.
In May of 2005, an observational program was carried out to investigate the along channel hydrodynamics and suspended sediment transport patterns at North Inlet, South Carolina. Along channel variability, which is important in establishing sediment transport pathways, has not been characterized for this system. Measurements of water column currents, salinity, bed sediment, suspended sediment concentration, and particle size distribution were obtained over a complete tidal cycle along the thalweg of the inlet entrance. Along channel currents, shear stress and bed sediment distributions vary significantly in space and time along a 3 km section bracketing the inlet throat. Most of the variability is consistent with geomorphic controls such as bed elevation variability and channel width. The highest velocities, shear stresses, suspended sediment concentration and bed sediment grain size are observed in the narrowest section of the inlet throat. Magnitudes systematically decrease along the channel toward the marsh as changes in channel geometry and branching reduces flow energy. Due to tidal asymmetry, the ebb phase contains significantly higher currents and associated sediment transport. Over the complete tidal cycle, depth integrated transport is directed towards the marsh landward of the intersection of Town and Debidue Creek. In contrast, net transport is out of the inlet seaward of this intersection. Sediment grain size distributions show 35% more material less than 63 μm on flood, suggesting net landward transport of fines. 相似文献
2.
海南岛洋浦港潮汐汊道口门的均衡过水面积 总被引：5，自引：1，他引：5
将汊道均衡与潮汐特征，纳潮量，淡水径流量及沉积物搬运格局相联系，确定了洋浦港的均衡条件，根据纳潮盆地的水面面积－水面高程曲线以及相关的特征潮位估算平均纳潮量，利用１９７７－１９７９年波浪观测资料和ＣＥＲＣ公式计算沿岸输沙率；此外，还用改进的Ｇａｄｄ公式确定口门涨、落潮流输沙率，计算中引入汊道口门流速频率分布函数的定义。由此而得洋浦港均衡过水面积为５８００ｍ＾２，与Ｏ＇Ｂｒｉｅｎ方法所得结果相比，本 相似文献
3.
潮沟系统水沙输运研究——以长江口崇明东滩为例 总被引：1，自引：1，他引：0
本研究以崇明东滩2015年4月实测潮间带水沙数据为基础,分析了潮沟、盐沼及光滩的水沙特征,重点研究了潮沟系统及邻近潮滩潮周期内悬沙通量情况。结果表明:（1）潮沟表层沉积物比潮滩细,二者平均中值粒径分别为21.7 μm和33.0 μm,悬沙粒径由海向陆逐渐变小;（2）大、小潮沟潮周期内潮流均以往复流为主,垂向平均流速分别为15.4 cm/s和34.6 cm/s;盐沼界和光滩则以旋转流为主,平均流速分别为11.3 cm/s和28.9 cm/s;（3）潮沟中的高悬沙浓度出现在涨潮初期,最大可达7.5 kg/m3,而潮滩高悬沙浓度则出现在潮落潮中期和高水位时刻;大、小潮沟和盐沼界站涨潮阶段平均悬沙浓度大于落潮阶段,光滩站则相反。潮沟悬沙主要来自邻近水域,而潮滩悬沙则与滩面表层沉积物密切相关;（4）潮沟在潮周期内净输沙方向均指向滩地,大潮沟潮周期单宽净输沙量可达4.0 t/m;盐沼界处垂直岸线和沿岸输沙强度相近,净输沙由海向陆,潮周期离岸输沙强度为1.0 t/m;光滩沿岸输沙强度远大于垂直岸线输沙,光滩净输沙由陆向海。研究揭示了潮间带潮沟系统的强供沙能力以及研究区域光滩冲蚀,盐沼植被带淤积的动力地貌过程。 相似文献
4.
长江河口北槽水沙过程对航道整治工程的响应 总被引：4，自引：3，他引：1
北槽大型航道整治工程确定了南北槽分汊口分流界线, 阻碍了北槽和邻近滩槽的水沙自由交换过程, 使北槽水沙动力过程发生调整。基于工程前后北槽主槽纵向同步水沙观测数据的统计分析表明:入口段落潮优势显著减弱;上段枯季时落潮优势显著减弱, 而洪季时落潮优势有所增强;中段(弯曲段拐点附近)落潮优势略有减弱;下段落潮优势明显加强。北槽主槽水沙纵向输移机制分析表明:欧拉余流、潮泵作用、斯托克斯效应和垂向环流为悬沙输移的主要驱动力, 其中欧拉余流输沙指向海, 斯托克斯输沙和垂向环流输沙指向陆, 而潮泵输沙随着季节而变化。洪季, 欧拉余流输沙和潮泵输沙在工程前后的变化使大潮期河床冲淤由中段和下段普遍落淤转化为中上段集中落淤。枯季, 工程前后稳定的潮流辐散输沙作用使大潮期河床以冲刷为主, 但工程后在入口段和上段潮泵的向上游输沙占优势, 使悬沙在入口段落淤。 相似文献
5.
Tidal inlets along the mesotidal coast of Maine contrast with those from other parts of the world by being dominated by flood-tidal
currents. Analysis of the factors responsible for flood or ebb dominance indicates factors external to the backbarrier environment.
We suggest that the flood dominance is caused by both a steepening of the tidal wave in the Gulf of Maine and the shallow
depth of the ebb-tidal delta and spit platform. Flood currents are typically 10–20 cm/sec stronger than the ebb at the inlet
throat. The flood dominance results in a significant net landward transport of sediment into the backbarrier. 相似文献
6.
Tidal inlets along the mesotidal coast of Maine contrast with those from other parts of the world by being dominated by flood-tidal currents. Analysis of the factors responsible for flood or ebb dominance indicates factors external to the backbarrier environment. We suggest that the flood dominance is caused by both a steepening of the tidal wave in the Gulf of Maine and the shallow depth of the ebb-tidal delta and spit platform. Flood currents are typically 10–20 cm/sec stronger than the ebb at the inlet throat. The flood dominance results in a significant net landward transport of sediment into the backbarrier. 相似文献
7.
To relate the textural characteristics of the bottom sediments of a tidal inlet to hydrodynamics, 45 sediment samples from the Tauranga Entrance to Tauranga Harbour were analysed for textural parameters, and tidal currents and waves were monitored. Tidal currents dominate sediment transport processes near the Tauranga Entrance although swell waves are significant on the ebb tidal delta, and wind waves may influence intertidal sediments within the harbour. The bulk of the sediment is probably derived from marine sand from the Bay of Plenty continental shelf, but tidal currents and waves have changed its textural character. In areas of swift tidal currents, particularly in the inlet channel itself, sediment is coarser, more poorly sorted, and more coarsely skewed than that in areas of slower currents. 相似文献
8.
江苏大丰海岸碱蓬滩潮沟及滩面的沉积动力特征 总被引：9，自引：3，他引：6
根据2002年7月在江苏大丰碱蓬滩潮沟观测的水文、悬沙、底质等资料,分析了潮沟的输水、输沙特征及悬沙和底质在粒径组成上的关系,结果表明,潮沟在流速、悬沙浓度、输水、悬沙输运、底质活动性等方面具有明显的涨落潮不对称.滩面归槽水占潮沟落潮输水量的33%,由此造成的悬沙输运量占潮沟落潮悬沙输运量的20%,这是导致潮沟涨落潮输水输沙不对称的主要因素.在一个潮周期中潮沟的净输水、净悬沙输运方向与滩面相反,指向落潮方向.悬沙和底质组成以粉砂和黏土为主,潮沟和滩面的悬沙粒径组成差别很小.悬沙是滩面底质的主要物质来源,两者在粒径组成上存在着必然联系,沉积物粒径与该粒级在底质中的含量与在悬沙中的含量之比具有明显的幂函数关系. 相似文献
9.
10.
长江口北港口门海域悬沙输运机制分析 总被引：1，自引：0，他引：1
根据2012年10月24日至11月1日在长江口北港口门海域获取的沉积动力学数据,采用输运通量分解方法分析水沙输运机制。结果表明,长江口北港口门附近海域涨、落潮期间底部悬沙浓度与近底部流速呈显著线性相关,存在显著的再悬浮作用;潮周期内的悬沙输运具不对称特征,涨潮悬沙浓度大于落潮悬沙浓度,悬浮泥沙有向陆输运的趋势。拉格朗日平流输运是影响悬沙输运的主要贡献项;潮泵效应(尤其是潮汐捕捉效应)以及河口垂向环流作用是两个次要影响因素,在影响程度上前者比后者略大。观测发现,长江口北港口门海域潮流除了具有涨落潮流速、历时等不对称现象外,还具有流速结构不对称的特征,进而导致涨、落潮底部湍流混合程度不对称与输沙不对称,这可能是造成悬沙向河口内输运形成最大浑浊带的重要因素。 相似文献
11.
粤西水东湾现代沉积环境特征与泥沙搬运路径 总被引：1，自引：0，他引：1
对粤西水东湾沉积地貌单元的现代沉积物分布特征分析与泥沙净搬运矢量计算表明，滨面斜坡沉积物主要由砂粒级物质组成，粒级参数Ｍｄ，ＱＤ和ＳＫ具有从海向岸、自东向西变化的总趋势，泥沙净搬运趋势以向岸和西北为主。落潮三角洲沉积物较其邻近滨面斜坡有所粗化，分选从中部向两侧变好，泥沙在落潮流与波浪驱动下沿落潮三角洲边缘向西运动。口门内潮汐通道深槽泥沙净搬运趋势指向湖。湖区的沉积物以泥质为主，分选中等至差，并形成绕涨潮三角洲的泥沙环流元。 相似文献
12.
The paper presents investigations of wave climate, tidal inlet hydraulics, and sand sediment bypassing at the entrance to Westport Harbour, South Island, New Zealand. The results complement and extend those of studies of bar morphologies and sediment characteristics already published. Longshore transport of about 1 × 106 m3/year is directed in a net eastward fashion across the inlet because of an in‐built misalignment of the harbour training walls. Approximately 90% of the drift is bypassed, and has been since 1921, by deflection and splitting of the main sediment streams through the inner and outer bars and a transverse channel aoross the entrance. The outer bar appears to be the submarine, downdrift extension of Carters Breach and river load appears to contribute an order of magnitude less sediment to the complex than annual littoral drift. River sediments and littoral drift are mixed off the harbour and a declining proportion over time is recirculated to cause progradation of North Beach. The tidal compartment contributes little to scour of the entrance because of the predominance of bar bypassing. Contrary to the recommendations of several past studies, it is argued that improvements in navigation depths at West‐port are more likely to be obtained through modification of the littoral drift system than they are from tidal compartment enlargement. 相似文献
13.
Process-based modeling of morphodynamics of a tidal inlet system 总被引：1，自引：0，他引：1
The morphodynamic evolution of an idealized inlet system is investigated using a 2-D depthaveraged process-based model,incorporating the hydrodynamic equations,Englund-Hansen’s sediment transport formula and the mass conservation equation.The model has a fixed geometry,impermeable boundaries and uniform sediment grain size,and driven by shore-parallel tidal elevations.The results show that the model reproduces major elements of the inlet system,i.e.,flood and ebb tidal deltas,inlet channel.Equilibrium is reached after several years when the residual transport gradually decreases and eventually diminishes.At equilibrium,the flow field characteristics and morphological patterns agree with the schematized models proposed by O’Brien (1969) and Hayes (1980).The modeled minimum cross-sectional entrance area of the tidal inlet system is comparable with that calculated with the statistical P-A relationship for tidal inlets along the East China Sea coast.The morphological evolution of the inlet system is controlled by a negative feedback between hydrodynamics,sediment transport and bathymetric changes.The evolution rates decrease exponentially with time,i.e.,the system develops rapidly at an early stage while it slows down at later stages.Temporal changes in hydrodynamics occur in the system;for example,the flood velocity decreases while its duration increases,which weakens the flood domination patterns.The formation of the multi-channel system in the tidal basin can be divided into two stages;at the first stage the flood delta is formed and the water depth is reduced,and at the second stage the flood is dissected by a number of tidal channels in which the water depth increases in response to tidal scour. 相似文献
14.
Li Jiufa 《海洋学报(英文版)》1991,10(1):117-127
The Nanhui tidal flat is located in the area of slow current where the ebb currents from the Changjiang Estuaryand the Hangzhou Bay converge and the flood current from the sea diverges into the estuary and the bay. The flat extends seaward in tongue shape and has a wide and gentle surface with a marked difference of tidal levels on its two sides, which results in the sediment longitudinal transport on the flat. The water-sediment conditions are diverse at different locations. The velocity and sediment concentration in intertidal zone are higher during the flood tide than those during the ebb tide. The net sediment transport is landward, resulting in a large amount of deposition of sediments on the shoal. However, the ebb current is the dominant one in deep-water area where the net sediment transport is seaward. There exist two circulation systems in plane view on the shoal and in its adjacent deep-water area, which results in the sediment exchanges between the flat and channel and between the estuary an 相似文献
15.
Current velocity and suspended sediment concentration measurements at anchor stations in the downstream extremity of the Gironde estuary indicate that during periods of high river discharge, a significant amount of suspended sediment is transported out of the estuary onto the adjacent continental shelf. The vertical profile of the residual (non-tidal) suspended sediment flux is similar to that of the residual current velocity, with a net upstream flux near the bottom and an overlying seaward-directed transport. The overall, depth-integrated result is a net seaward transport of suspended sediment out of the estuary. It appears that this net seaward transport varies directly with tidal amplitude.Aerial photography and water sampling indicate that during high river inflow, the downstream extremity of the turbidity maximum extends onto the continental shelf at ebb tide. The tidal and coastal current patterns of the inlet and inner shelf induce a northward transport of the turbid estuarine water, and at each tidal cycle, a certain amount of suspended sediment leaves the estuary; part of this sediment is deposited in a silt and clay zone on the continental shelf. 相似文献
16.
《Coastal Engineering》2006,53(5-6):505-529
Texel inlet, the largest inlet in the Dutch Wadden Sea, has undergone drastic changes in the morphology of basin, ebb-tidal delta and adjacent coastlines after closure of a major part of its back-barrier basin. Despite intensive monitoring and analysis, present observation-based conceptual models lack the subtle physics necessary to explain the sand exchange between inlet, ebb-tidal delta and adjacent coastlines.Fundamental understanding of the inlet dynamics and evolution is obtained by integrating field and model data analysis. The state-of-the-art process-based model Delft3D Online Morphology has been used to generate synoptic data of high spatial and temporal resolution over the inlet domain. It is shown that the Delft3D Online Morphology model is capable of the quasi real-time simulation of the dominant flow and transport patterns over a 3-month period on the scale of the inlet. The high-resolution numerical model results prove to be a valuable tool in identifying the main transport patterns and mechanisms in the inlet domain. Qualitative transport patterns in Texel Inlet and its associated ebb-tidal delta are derived by integration of the observations and model results.The present ebb-tidal delta developments are best described as a second-stage self-organizing phase of redistribution and recirculation of sediments to obtain a natural dynamic equilibrium state, adapted to the changed configuration of the main-ebb channels. Sand is transported from the abandoned ebb-delta front (western margin of Noorderhaaks) and along the adjacent coastlines into the basin where it partly settles. Ebb-tidal currents redistribute sand back from the basin mainly onto the southern ebb-tidal delta shoals. Large gross transport rates, but small morphological changes, point to sediment recirculation. Sediment import into the basin results from net flood dominated transport due to tidal asymmetry, landward directed wind- and wave-driven flow, and larger flood transport capacities due to wave effects (e.g. enhanced bed shear stresses and stirring of sediment) that exceed the net ebb-dominated tidal residual transports. 相似文献
17.
18.
《Coastal Engineering》2005,52(2):159-175
The Frisian Inlet is one of the tidal basins of the Dutch Wadden Sea. In 1969, its basin area was reduced by 30%. As documented by bathymetric surveys, this has led to an import of sediment of 30×106 m3 over the first 18 years. The study presented in this paper seeks to establish the mechanisms responsible for the passage of the sediment through the throat cross-section of the inlet channel. Emphasis is on a 14-day period of relative calm when sediment transport can be attributed solely to tidal currents. Use is made of continuous measurements of velocity, sand and silt concentration. The measurement station was located on one side of the throat cross-section in a water depth of approximately 6 m. For both the sand and silt fraction of the sediment, suspended load transport is the dominant transport mode. It is shown that for sand, concentration variations and net transport are determined by the local (in the throat section) velocity. Especially the residual velocity and tidal velocity asymmetry play an important role in the net sand flux. For silt, except for transport associated with locally generated vertical mixing, the net transport is largely determined by sedimentation–erosion processes in the basin and the silt concentration in the North Sea. Comparison with measurements in a station located in the middle of the throat section shows considerable difference in residual velocity and tidal velocity asymmetry. As a result, the sediment fluxes also differ. Accurately determining the net sediment flux in the throat section would require a dense net of measurement stations. 相似文献
19.
山东荣成月湖潮汐汊道的时间-流速不对称特征 总被引：3，自引：3，他引：3
月湖是山东半岛东端的一个小型潮汐汊道.在月湖进行了潮位、潮汐观测及地形测量,运用两种方法从潮位记录推算出口门落潮主干道垂线平均流速和断面平均流速.发现除涨潮优势型和落潮优势型外,月湖还表现出另外两种时间-流速不对称,即涨潮历时大于落潮历时且涨潮流速大于落潮流速、涨潮历时小于落潮历时且涨潮流速小于落潮流速.月湖的时间-流速不对称特征与不规则潮汐、涨(落)潮的流速跟潮位的匹配关系、汊道口门的断面形态、口门特殊的水流结构及循环过程等因素有关.时间-流速不对称类型的研究,对于理解潮汐汊道系统的沉积动力行为及进行人工整治有一定意义. 相似文献
20.
本文基于4次洪枯季同步水文观测资料,着重分析了长江口北支悬沙浓度的潮周期变化、垂向分布、纵向分布和悬沙输移及其时空差异。研究结果显示,悬沙浓度的潮周期变化过程在大中潮期以M型(双峰型)为主,下段主槽内在大潮期多出现V型,上段在枯季可出现涨潮单峰型;小潮期可出现无峰、单峰或双峰型。涨、落潮悬沙浓度峰值及均值,在枯季多涨潮大于落潮,洪季中小潮特别是小潮期易出现落潮大于涨潮;下段主槽内在大潮期易出现落潮大于涨潮。悬沙浓度的垂向分布及其变化特点,在大中潮期与悬沙的潮周期变化型式有关,其中M型存在显著的洪枯季差异。纵向上,最高悬沙浓度在枯季出现于中段灵甸港至三和港之间及附近河段,洪季则在下段三条港附近。潮周期悬沙净输移,枯季大多向陆特别是大中潮期,洪季中上段大多向海,下段大潮期多向陆、中小潮易出现向海;下段主槽内在大潮期易出现向海。 相似文献