共查询到20条相似文献，搜索用时 31 毫秒
1.
鸭绿江河口地区沉积物特征及悬沙输送 总被引：13，自引：1，他引：13
根据鸭绿江河口区4个站位的潮周期测量数据和3个柱状样的粒度数据，对悬沙的输送规律以及口门地区最大浑浊带的形成机制、悬沙输送方向以及物质来源和动力条件进行了分析。计算分析表明，鸭绿江是一条落潮流占优势的河流，平均流作用、斯托克斯漂移效应以及水深与悬沙浓度的潮变化引起的悬沙输送是其河口区最主要的悬沙输送机制。3个柱状样粒度参数自东向西的变化反映了鸭绿江辽口西侧沿岸地区动力条件和沉积环境的变化：沉积物的平均粒径变小，分选变差，并且更正偏，物源的多元化特征逐渐增强。物源和河口区沿岸沉积动力环境的差异以及潮相的周期变化使3个柱状样中的环境敏感粒度组分对应着不同的粒径分布区间。 相似文献
2.
黄河口悬浮泥沙时空动态及其驱动机制 总被引：1，自引：1，他引：0
受径流输沙、风浪、潮汐等影响,河口近岸海域悬浮泥沙具有显著的时空变化。本文基于小时分辨率的GOCI遥感影像,利用最优遥感反演算法,结合空间分析和统计方法,深入研究黄河口及邻近海域悬沙时空动态特征及驱动机制。结果表明,径流输沙对悬沙浓度的影响以河口近岸区为主,高径流输沙对悬沙浓度分布影响可达距岸约20 km,并向孤东近岸方向扩散。大风可引起清水沟老河口区泥沙强烈再悬浮,形成高浓度悬沙区。涨落潮对小时尺度的悬沙浓度影响显著,并影响悬沙的南北扩散。大潮悬沙浓度变化和扩散范围均大于小潮,潮流流速不同是造成该差异的主要原因。水深与悬沙浓度之间存在较明显的负相关关系,根据不同驱动因素的差异,悬沙浓度随着水深的增加呈现出指数型、幂函数型、线性3种关系。 相似文献
3.
黄河口快速沉积及其动力过程 总被引：2，自引：1，他引：2
现场观测资料和卫星遥感校准图像计算表明 ,185 5年以来 ,黄河三角洲新淤陆地 36 99km2 ,生长速率为 2 6 8km2 /a ,黄河输入三角洲 1× 10 8t泥沙形成 3 14 4km2 的陆地。进入河口区的泥沙约 88 4 %堆积在水下 8km宽的三角洲前缘。研究表明 ,这一堆积比例是河口切变锋、异重流和潮流场相互作用的结果 ,异重流在黄河汛期一直存在 ,大约搬运黄河来沙的 6 0 %沉积在三角洲前缘 ;一个潮周期内 ,切变锋出现两次 ,它能够捕获异轻羽状流中的悬浮泥沙堆积 ,也能够限制异重流的远距离扩散。切变锋消失后 ,少量悬浮泥沙才能远距离扩散 ,随潮流离开三角洲水下斜坡。 相似文献
4.
Shuqing Qiao Xuefa Shi Aimei Zhu Yanguang Liu Naishuang Bi Xisheng Fang Gang Yang 《Estuarine, Coastal and Shelf Science》2010,86(3):337-344
Hydrological and sedimentological investigations were carried out off the Yellow River (Huanghe) mouth and the nearby Bohai Sea during August–September 2007 to examine the distribution and transport of suspended sediments. Our data witnessed that suspended sediments from the Yellow River mouth primarily extend southerly and southeasterly during the flood season. High suspended sediment concentration (SSC) occurs as turbid plume on both sides of the river mouth, where it can reach >20 mg l?1 in the surface water and >40 mg l?1 in the bottom water. Accordingly, salinity varies from 25 to 29 psu, mean grain size (Dmz) is >200 μm, and volume concentration (VC) is >100 μl l?1. High SSC was concentrated in the river mouth area as two muddy patches, i.e. the North Mud and South Mud, consisting mostly of fine-grained silt and clayey silt sediments. Our results have verified the larger extent of the South Mud than that of the North one, implicating south- and southeastward sediment dispersal paths that prevail near the river mouth area. The existing anti-clockwise and clockwise flows in the river mouth area were synthesized as the major hydrodynamics responsible for forming the two muddy patches. Tidal and residual currents are considered as the key hydrodynamic factors controlling the sediment distribution and transport in the region. 相似文献
5.
Eric Wolanski Robert H. Richmond Gerald Davis Victor Bonito 《Estuarine, Coastal and Shelf Science》2003,56(5-6):1029-1040
Fouha Bay is a 400-m-long funnel-shaped, 10-m-deep, coral-fringed embayment on the southwest coast of Guam. It drains a small catchment area (5 km2) of steeply sloping, highly erodible lateritic soils. River floods are short-lived and the sediment load is very large, with suspended sediment concentration (SSC) exceeding 1000 mg l−1. The resulting river plume is about 1 m thick and is pulsing in a series of 1–2 h-long events, with outflow velocity peaking at 0.05 m s−1. Turbulent entrainment results in an oceanic inflow at depth into the bay. As soon as river flow stops, the plume floats passively and takes 5 days to be flushed out of Fouha Bay. The suspended fine sediment flocculates in 5 min and aggregates on ambient transparent exopolymer particles to form muddy marine snow flocs. In calm weather, about 75% of the riverine mud settles out of the river plume into the underlying oceanic water where it forms a transient nepheloid layer. This mud ultimately settles and is trapped in Fouha Bay. Under typhoon-driven, swell waves, the surface plume is at least 7 m thick and bottom entrainment of mud results in SSC exceeding 1000 mg l−1 for several days. It is suggested that successful management of fringing coral reefs adjacent to volcanic islands may not be possible without proper land use management in the surrounding catchment. 相似文献
6.
7.
Sherry M. Lippiatt Matthew T. Brown Maeve C. Lohan Carolyn J.M. Berger Kenneth W. Bruland 《Estuarine, Coastal and Shelf Science》2010
This study examines the distribution of leachable particulate iron (Fe) in the Columbia River, estuary, and near-field plume. Surface samples were collected during late spring and summer of 2004–2006 as part of four River Influence on Shelf Ecosystems (RISE) cruises. Tidal amplitude and river flow are the primary factors influencing the estuary leachable particulate Fe concentrations, with greater values during high flow and/or spring tides. Near the mouth of the estuary, leachable particulate Fe [defined as the particulate Fe solubilized with a 25% acetic acid (pH 2) leach containing a weak reducing agent to reduce Fe oxyhydroxides and a short heating step to access intracellular Fe] averaged 770 nM during either spring tide or high flow, compared to 320 nM during neap tide, low flow conditions. In the near-field Columbia River plume, elevated leachable particulate Fe concentrations occur during spring tides and/or higher river flow, with resuspended shelf sediment as an additional source to the plume during periods of coastal upwelling and spring tides. Near-field plume concentrations of leachable particulate Fe (at a salinity of 20) averaged 660 nM during either spring tide or high flow, compared to 300 nM during neap tide, low flow conditions. Regardless of tidal amplitude and river flow, leachable particulate Fe concentrations in both the river/estuary and near-field plume are consistently one to two orders of magnitude greater than dissolved Fe concentrations. The Columbia River is an important source of reactive Fe to the productive coastal waters off Oregon and Washington, and leachable particulate Fe is available for solubilization following biological drawdown of the dissolved phase. Elevated leachable Fe concentrations allow coastal waters influenced by the Columbia River plume to remain Fe-replete and support phytoplankton production during the spring and summer seasons. 相似文献
8.
Numerical experiments in an idealized river mouth are conducted using a three-dimensional hydrodynamics model (EFDC model) to examine the impacts of suspended sediment concentration (SSC), settling velocity of sediment and tidal mixing on the formation and maintenance of estuarine hyperpycnal flows. The standard experiment presents an illustrative view of hyperpycnal flows that carry high-concentrated sediment and low-salinity water in the bottom layer (>1.0 m in thickness) along the subaqueous slope. The structure and intra-tidal variation of the simulated hyperpycnal flows are quite similar to those previously observed off the Huanghe (Yellow River) mouth. Results from the three control experiments show that SSC of river effluents is the most important parameter to the formation of hyperpycnal flows. High SSC will increase the bulk density of river effluents and thus offset the density difference between freshwater and seawater. Low SSC of river effluents will produce a surface river plume, as commonly observed in most large estuaries. Both the settling velocity of sediment particles and the tidal mixing play an important role in maintaining the hyperpycnal flows. Increasing settling velocity enhances the deposition of sediment from the hyperpycnal layer and thus accelerates the attenuation of hyperpycnal flows, whereas increasing tidal mixing destroys the stratification of water column and therefore makes the hyperpycnal flows less evident. Our results from numerical experiments are of importance to understand the initiation and maintenance of hyperpycnal flows in estuaries and provide a reference to the rapidly decaying hyperpycnal flows off the Huanghe river mouth due to climatic and anthropogenic forcing over the past several decades. 相似文献
9.
《Marine Geology》2004,203(1-2):95-107
With the goal of improving understanding of the effect of flocculation on the formation of fine-grained deposits on continental shelves, hydrographic profiling, in situ imaging of suspended matter, and collection of surficial sediment samples were conducted at the Po River Delta in June 2001. These data show that during medium flow conditions (1920 m3/s), sedimentation occurs rapidly immediately offshore of the main distributary, Po della Pila. Rapid sedimentation is promoted by large rapidly sinking flocs forming in the river well upstream of the mouth. The delivery of fine sediment to the seabed at the mouth of the Po is sufficient to overwhelm the erosive effects of waves and currents, leading to accumulation of mud in water depths as shallow as 4 m. On cross-shelf transects 2 km north and south of the mouth, however, suspended sediment supply from the river is reduced to the point that mud accumulates only seaward of the 8-m isobath. Along the central transect, suspended sediment concentration decreases rapidly seaward of the 6-m isobath where the emergence of a more organic-rich population of flocs along a mid-water density interface is suggested. Energetic activity along the 15-m isobath likely promotes resuspension with the potential for removal of material from the delta. Further investigation of floc properties, namely the relationship of floc size to settling velocity, is necessary to establish the degree to which the suspension is flocculated during transport and deposition. 相似文献
10.
Dispersion of disposed dredged slurry in the meso-tidal Changjiang (Yangtze River) Estuary 总被引：2，自引：0，他引：2
Jiaxue Wu James T. Liu Huanting Shen Shuying Zhang 《Estuarine, Coastal and Shelf Science》2006,70(4):663
To understand the dispersal pattern of sediment plume and its controlling processes, a field experiment of concentrated slurry dispersal created by a dredger was conducted in the Changjiang (Yangtze River) Estuary during the 2002 flood season. An acoustic suspended sediment concentration profiler and an acoustic Doppler profiler were deployed to simultaneously observe suspended sediment concentrations (SSC) and tidal currents at the pre-selected sections shortly following the release of dredged materials. Water sampling, grab sampling and shallow coring were simultaneously carried out to obtain the SSC and grain-size texture. High-resolution SSC profiler observations showed that two distinct sediment plumes (middle level- and near-bed plumes) occurred during the intermediate tidal phase between the spring and neap due to differential settling of the sediment mixture, whereas only a benthic plume occurred due to rapid flocculation settling during the neap tide. Three subsequent stages can be identified during the dispersal of the sediment plume: (1) initially stable stage before the release; (2) unstable stage shortly following the release as a settling cloud; and (3) stable stage after the formation of a primary lutocline or a benthic plume. Enhanced mixing due to oscillatory shear flows could raise only the elevation of the lutocline in the slurry, but could not enhance the transport capacity of suspension. In the presence of high concentration, the fate of bottom sediment plume was controlled by the bottom stress, independent of the interfacial mixing. 相似文献
11.
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
12.
长江河口最大浑浊带含沙量垂线分布状态的分析 总被引：2，自引：0，他引：2
计算表明,潮泵效应在长江河口最大浑浊带悬沙输移中起着重要的作用。含沙量垂线分布的潮周期变化反映悬沙与床沙之间存在双向交换。据此讨论了最大浑浊带与拦门沙的关系。 相似文献
13.
长江口南北槽分流口洪季水沙变化过程研究 总被引：1，自引：0，他引：1
河口分流口的水沙变化过程是影响河口三角洲发育的核心环节,对下游河势的稳定起着关键性的作用。本文通过对北槽二、三期工程前后的南北槽分流口河段洪季大潮期间的同步水沙观测数据进行分析,以探讨长江口深水航道工程整治对分流口水沙过程的影响。结果表明:(1)北槽二期工程到三期工程后,分流口洪季以落潮优势流、优势沙为主的格局基本没有发生改变,但南槽优势流、优势沙出现略有变大,而北槽略有变小现象;(2)分流口洪季的水体输移主要受控于欧拉余流的变化,除北槽入口段水体净输移量一直较小外,其他河段在二、三期工程实施期间均有大幅提升,其中斯托克斯余流变化不大,拉格朗日余流与欧拉余流变化相一致,南槽呈波动状上升,北槽先增后减;(3)在二期到三期工程期间,北槽分流比明显减小,入口段落潮流速减小,含沙量较高,水体输移量降低,输沙强度减弱,由此导致二期工程以来北槽入口河段淤积强度加重。 相似文献
14.
15.
16.
贴体正交曲线坐标系下水流泥沙数学模型的构建与应用 总被引：1，自引：0，他引：1
为了研究深圳河河口福田保税区围垦填土占用部分河道对深圳河治理工程防洪能力和河床冲淤变化的影响情况，建立了贴体正交曲线坐标系下的平面二维的深圳河河道-河口-海湾整体水域的水流泥沙数学模型，模型中采用双步全隐有限差分法离散求解水流运动方程，悬沙不平衡输运方程采用三阶QUIKEST格式离散后用交错方向法求解。在经实测水文资料验证的基础上，应用数学模型计算了8种洪峰流量和河口高潮位组合4种围垦填土的挖除方案下深圳河沿程水位和河床冲淤变化，讨论了深圳河治理工程防洪能力降低的程度和近河口段洲滩冲刷以及所造成香港一侧红树林的破坏情况，提出了优化挖除方案。 相似文献
17.
河口羽流是河口冲淡水在陆架中扩展的主要形式, 其扩展受到诸多动力与地形因素的影响, 口门拦门沙就是其中之一。以一个理想化的河口为例, 采用区域海洋模型(regional ocean modelling system, ROMS), 研究口门拦门沙对河口羽流扩展的影响, 具体包括拦门沙对羽流的出流状态、扩展范围以及远场区沿岸流淡水输运的影响。研究结果表明, 拦门沙增加了口门处的水体分层, 减小了羽流出流速度, 增大了羽流凸出体的半径, 减小了远场区沿岸流宽度, 并进而减少了沿岸流中的淡水输送。本项研究对地形因素对河口羽流的扩展研究以及陆源物质的向海输运等均具有重要意义。 相似文献
18.
于2005年5月大潮期间在杭州湾北部潮流深槽区的4个站位进行潮周期观测,获得了流速、悬沙等数据,并对其进行了分析,计算了水沙通量和再悬浮通量。分析结果表明,该深槽区涨潮流速大于落潮流速,涨潮历时小于落潮历时,潮差自湾口向湾内方向增大;悬沙的组分以粉砂为主,分选较差,偏态以负偏为主,这些特征与底质一致;深槽中部和东部的悬沙沿岸线向湾内方向输运;深槽西部和东部外侧的悬沙输运方向与余流方向一致,分别向湾内和南部输运;除转流和流速加速初期外,垂线流速分布符合Kûrmûn-Prandtl模型,摩阻流速与垂线平均流速变化趋势一致。计算得到的表观粗糙长度在涨落潮时段的水流加速或减速阶段都呈增大趋势,且数值较大,这难以把它简单地归结为床面形态的作用,表观粗糙长度的变化趋势可能是高悬沙浓度和浓度成层性共同作用的结果,但对这一假说的验证还有待于进一步的现场观测和机制分析。计算所得的再悬浮发生的周期性与实测悬沙浓度的周期性相符,而且最大悬沙浓度的出现滞后于最大再悬浮通量,说明再悬浮作用对水层中悬沙浓度的变化具有重要影响。 相似文献
19.
An enhanced MODIS remote sensing model for detecting rainfall effects on sediment plume in the coastal waters of Apalachicola Bay 总被引：1，自引：0，他引：1
Mapping of total suspended solids (TSS) was conducted to investigate rainstorm-induced characteristic of sediment plume in the coastal waters of Apalachicola Bay. An improved TSS quadratic polynomial regression model (Calibration: R2=0.8586, N=32; validation: RMSE of 4.76 mg/l, N=30) for MODIS remote sensing was presented in this study. TSS mapping of MODIS before and after a rainstorm event showed distinct temporal-spatial variability of TSS concentration. Driven by ocean tidal current, a storm plume of width at about 40-50 km was formed flowing towards southwest of study area. The distinct boundary separating the highly turbid (west side) and relatively clear water (east side) was found near Sikes Cut. Further, by taking the TSS mapping under the low river discharge condition due to a local rainstorm as a reference of background TSS, two thresholds of TSS (25 and 45 mg/l respectively) were used to estimate the range of rainstorm plume and the central area of sediment load from surrounding land, and the spatial extent and evolution of the sediment plume during the local rainstorm. Besides, it was found that the storm plume concentration of TSS at east side of Sites Cut was quickly diluted under 25 mg/L, forming a storm plume towards east with width at about 7-8 km. The method developed in this study may be used to support coastal storm water research and management activities. 相似文献
20.
港湾深槽骤淤的条件探讨 总被引：4，自引：0，他引：4
深槽骤淤指深槽底部在特定条件下产生的快速淤积,通常以浮泥形式出现.综合分析杭州湾、三门湾和象山港的地形地貌、水文泥沙及深槽固定剖面风暴前后或大、小潮期间的地形变化得出港湾深槽产生骤淤的基本条件:(1)有丰富的细颗粒物质的供应源;(2)迅速衰减的动力条件;(3)存在明显的负地形.三个条件必须同时得到满足,深槽才能产生骤淤.杭州湾泥沙来源丰富,终年悬沙浓度高,东试挖槽附近受长江冲淡水次级锋面和钱塘江冲淡水锋面影响较大,因此在一个大小潮周期内水动力条件减弱时挖槽处可产生骤淤.三门湾泥沙来源较丰富,正常天气的年份内潮滩处于缓慢淤积状态,而深槽处于冲淤基本平衡状态,但在风暴等灾害性天气下发生强烈的滩、槽泥沙交换,若风暴后处于中小潮汛期则深槽发生骤淤.象山港由于环境隐蔽,水清沙少,沿岸潮滩狭窄,缺少骤淤的物源,即使风暴作用后鹰龙山深槽也没有产生骤淤. 相似文献