珠江黄茅海河口洪季侧向余环流与泥沙输移   总被引：1，自引：1，他引：0  

杨名名  吴加学  张乾江  任杰  刘欢 《海洋学报》2016,38(1):31-45

2012年洪季对珠江黄茅海河口湾侧向动力结构与泥沙输移过程进行了系统观测,采用动量平衡和泥沙通量机制分解等方法,分析了河口流、温盐和泥沙侧向分布特征以及泥沙输移过程,探讨了侧向动量平衡与泥沙输移机制。洪季黄茅海河口存在明显的侧向流,西滩和北槽均形成表层向东、底层向西的两层侧向流,拦门沙滩顶呈现表、底层向西、中层向东的三层侧向流,而拦门沙前缘侧向流整体向西。河口湾纵向净泥沙通量表现为北槽向海、西滩向陆,拦门沙滩顶及其前缘均向海;侧向净泥沙通量表现为滩顶及其前缘均向西,西滩向东、北槽向西。这种侧向泥沙辐聚过程是高浓度悬沙聚集于滩槽界面的重要原因,向陆净通量是西滩回淤的重要原因。滩槽间侧向余环流动量平衡主要是侧向斜压梯度力、科氏力和侧向平流作用。欧拉平流输运在侧向泥沙输运中起主要作用,潮泵效应也起重要作用。  相似文献   

Development and Extension of An Aggregated Scale Model: Part 1 – Background to ASMITA     

Ian TOWNEND  Zheng Bing WANG  Marcel STIVE  Zeng ZHOU 《海洋工程》2016,(4):483-504

Whilst much attention has been given to models that describe wave, tide and sediment transport processes in sufficient detail to determine the local changes in bed level over a relatively detailed representation of the bathymetry, far less attention has been given to models that consider the problem at a much larger scale (e.g. that of geomorphological elements such as a tidal flat and tidal channel). Such aggregated or lumped models tend not to represent the processes in detail but rather capture the behaviour at the scale of interest. One such model developed using the concept of an equilibrium concentration is the Aggregated Scale Morphological Interaction between Tidal basin and Adjacent coast (ASMITA). In this paper we provide some new insights into the concepts of equilibrium, and horizontal and vertical exchange that are key components of this modelling approach. In a companion paper, we summarise a range of developments that have been undertaken to extend the original model concept, to illustrate the flexibility and power of the conceptual framework. However, adding detail progressively moves the model in the direction of the more detailed process-based models and we give some consideration to the boundary between the two.  相似文献   

长江河口主槽地貌形态观测与分析   总被引：4，自引：3，他引：1  

吴帅虎  程和琴  胥毅军  李九发  郑树伟  徐韦  陆雪骏 《海洋工程》2016,34(6):65-73

人类活动可以改变流域至河口的泥沙输运与沉积。尽管一些近期的研究已经调查了长江河口的形态演变,然而,流域和河口工程如何影响河口河床的形态演变仍然是不清楚的。该文利用2010年至2015年多波束测深系统和浅地层剖面仪等先进现场测量仪器的长江口主槽走航测量资料,并结合主槽表层沉积物资料,分析了近年来人为强干扰下的长江河口主槽底床微地貌形态,以理解近期人类活动对河口的影响。结果显示:近年来长江河口主槽底床上除了存在平床、沙波、冲沟和冲刷痕等常见微地貌形态外,还存在着疏浚痕和凹坑等人为微地貌形态。在流域和河口大型工程的共同影响下,近年来南北港中上段、横沙通道和南槽上段均受到不同程度的冲刷,其主槽底床上呈现出不同程度冲沟和冲刷痕等侵蚀性微地貌。而由于疏浚工程的影响,南港下段、圆圆沙航槽和北槽航道底床上出现了大范围的疏浚痕和凹坑。近年来包括南槽上段、北槽主槽中段和下段的局部区域和北港拦门沙河段局部区域在内的长江河口最大浑浊带的河床沉积物有粗化趋势。南北港中上段和横沙通道的大部分区域均发育了大量沙波微地貌;总体上,长江河口沙波的波高在0.12~3.12 m,波长在2.83~127.89 m,波高/波长在0.003~0.136,长江河口中上段的沙波尺度(波高的均值为0.91 m,波长的均值为20.08 m)大于密西西比河下游(波高的均值为0.87 m,波长的均值为17.62 m),且两区域沙波的几何形态差异性较小。  相似文献   

长江口邻近海域夏季大型底栖生物群落特征     

杨梅  李新正  王洪法  张宝琳 《海洋科学集刊》2016,51(51):269-278

本文根据2014年6月长江口邻近海域大型底栖生物的调查资料, 采用优势度指数, 物种多样性指数、丰富度指数、均匀度指数, Bray-Curtis相似性聚类和非参数多维标度排序(nMDS)标序方法, 分析了长江口邻近海域夏季大型底栖生物的群落特征。本次调查共采集大型底栖生物135种, 其中多毛类66种, 甲壳动物33种, 棘皮动物14种, 软体动物13种, 其他类群9种。调查海域的大型底栖生物平均丰度为122.2ind/m₂,平均生物量为7.8g/ m₂。丰度、生物量和多样性指数在不同海区间的空间差异均不显著。大型底栖生物在20%的相似性水平上可以划分为8个群组,各站位间相似性水平较低。ABC曲线表明,伴随海岸带开发及人类活动的持续影响, 长江口邻近海域底栖生境的稳定性受到轻微扰动, 建议继续开展长期连续的监测, 为研究长江口海域环境变化和大型底栖生物群落演替提供基础资料。  相似文献   

Zooplankton community structure in a highly turbid environment (Charente estuary,France): Spatio-temporal patterns and environmental control   总被引：1，自引：0，他引：1  

Julien Modéran  Pierre Bouvais  Valérie DavidSandrine Le Noc  Benoit Simon-BouhetNathalie Niquil  Pierre MiramandDenis Fichet 《Estuarine, Coastal and Shelf Science》2010

Zooplankton assemblages were studied from January 2007 to January 2008 along the salinity gradient of the Charente estuary (France). A Lagrangian survey was performed monthly at five sampling stations defined by salinity (freshwater, 0.5, 5, 15 and 25) in order to collect zooplankton and measure the main environmental parameters (concentrations of suspended particulate matter, particulate organic carbon, chlorophyll a and phaeopigments). A combination of multivariate cluster analysis, species indicator index and canonical correspondence analysis was used to relate the spatio-temporal patterns of the zooplankton assemblages with environmental drivers. The estuary was divided into three different zones by means of environmental parameters while four zooplankton assemblages were identified along the salinity gradient. The Charente estuary appeared as one of the most turbid systems in Europe, with suspended particulate matter (SPM) concentration reaching 3.5 g l⁻¹ in the Maximum Turbidity Zone (MTZ). Algal heterotrophy and microphytobenthos resuspension from the wide mudflats could be responsible for the relatively high chlorophyll a concentrations measured within this MTZ. Salinity and SPM affected significantly the spatial distribution of zooplankton species while temperature and river flow seemed to control their temporal variations. From a zooplanktonic viewpoint, the highly turbid Charente estuary seemed to match an “ecotone–ecocline” model: the succession of species assemblages along the salinity gradient matched the concept of ecocline while the MTZ, which is a stressful narrow area, could be considered as an ecotone. Although such ecoclinal characteristics seemed to be a general feature of estuarine biocenoses, the ecotone could be more system-specific and biological compartment-specific.  相似文献   

The effect of a storm surge event on the macrophytes of a temporarily open/closed estuary,South Africa     

T. Riddin  J.B. Adams 《Estuarine, Coastal and Shelf Science》2010

Temporarily open/closed estuaries typically open to the sea due to freshwater inflow coupled with storm surge events. In September 2008, in the absence of freshwater inflow, the mouth of the East Kleinemonde Estuary breached in response to a storm surge. The mouth of the estuary closed the following day at a high level. Marine overwash events following the breach introduced large volumes of saline water into the estuary and raised the water level by 0.07–0.33 m. Salinity was significantly higher in the 15 month closed phase after the breach (31 ± 0.9) compared to 21.9 ± 0.9 in the closed brackish phase before the breach. The historical average salinity for the estuary during a closed period is 23–25. The increase in salinity has reduced submerged macrophytes Ruppia cirrhosa and Chara vulgaris cover by 38.1%. Macroalgal cover of species such as Dictyota dichotoma, Caulacanthus ustulatus, Codium tenue and Ulva spp. have increased by 7.9%. The saline high water levels have also significantly reduced supratidal salt marsh cover by 15.2%, and reed and sedge cover by 19.7%. Loss of these habitats may result in bank destabilisation and erosion. This is the first record of an extended saline period in the 15 years the estuary has been monitored. Sea level rise in association with climate change, together with localised freshwater inflow reduction is likely to result in an increase in marine overwash events. The frequency and duration of closed saline periods are likely to increase in this type of estuary. A loss of submerged macrophytes may have significant impacts on faunal composition and abundance and on the subsequent functioning of temporarily open/closed estuaries. This has serious ecological implications since these estuaries represent 70% of the different types of estuaries found in South Africa.  相似文献   

Distribution and possible sources of organochlorine residues in sediments of a large urban estuary,Port Jackson,Sydney     

G. F. Birch  S. E. Taylor 《Australian Journal of Earth Sciences》2013,60(4):749-756

Sydney Harbour is surrounded by a large capital city of about four million people and its highly urbanised (86%) catchment supports a substantial industrial base and an extensive transport infrastructure. Large commercial and naval ports occupy the waterway and the harbour is an important recreational area. Surficial sediment in Sydney Harbour contains high concentrations of PCBs, HCB, total chlordane, total DDT, aldrin, dieldrin, heptachlor and heptachlor‐epoxide, but low concentrations of lindane. PCBs, total chlordane, and to a lesser extent dieldrin, are most elevated in sediment in creeks on the southern shores of the harbour suggesting sources within older, highly urbanised/industrialised catchments of western‐central Sydney. There are high concentrations of total DDT and HCB in sediments of the upper harbour and Homebush Bay suggesting that chemical industries on the shores of the estuary in this area are sources of these contaminants. Although no sediment quality guidelines apply in Australia, empirically derived biological effects criteria suggest that sediment over extensive areas of Sydney Harbour may have an adverse impact on biota. Especially of concern are sediments containing high concentrations of chlordane and DDT.  相似文献   

九龙江河口区现代沉积环境及其物质输运趋势   总被引：1，自引：0，他引：1  

方建勇  陈坚  王爱军  李东义  黄财宾 《海洋地质与第四纪地质》2010,(2)

对九龙江河口区58个表层沉积物样品进行了激光粒度分析,并分别应用系统聚类分析和GSTA模型分析,探讨了研究区的沉积特征、沉积环境和表层沉积物输运趋势。结果表明,九龙江河口区表层沉积物由10种沉积物类型组成,与20世纪80年代相比,该海区底质沉积物在类型分布和粒径粗细上发生了一定的变化;将研究区划分为3种与沉积动力特征相对应的主要沉积环境区;表层沉积物输运趋势因受该区特殊的地形和复杂的水动力条件影响而表现为北进南出,海门岛西北海域形成逆时针方向输运趋势,而海门岛以东海域形成三向汇聚的输运趋势。  相似文献   

Capabilities of the bathymetric Hawk Eye LiDAR for coastal habitat mapping: A case study within a Basque estuary   总被引：1，自引：0，他引：1  

Guillem Chust  Maitane Grande  Ibon Galparsoro  Adolfo Uriarte  Ángel Borja 《Estuarine, Coastal and Shelf Science》2010

The bathymetric LiDAR system is an airborne laser that detects sea bottom at high vertical and horizontal resolutions in shallow coastal waters. This study assesses the capabilities of the airborne bathymetric LiDAR sensor (Hawk Eye system) for coastal habitat mapping in the Oka estuary (within the Biosphere Reserve of Urdaibai, SE Bay of Biscay, northern Spain), where water conditions are moderately turbid. Three specific objectives were addressed: 1) to assess the data quality of the Hawk Eye LiDAR, both for terrestrial and subtidal zones, in terms of height measurement density, coverage, and vertical accuracy; 2) to compare bathymetric LiDAR with a ship-borne multibeam echosounder (MBES) for different bottom types and depth ranges; and 3) to test the discrimination potential of LiDAR height and reflectance information, together with multi-spectral imagery (three visible and near infrared bands), for the classification of 22 salt marsh and rocky shore habitats, covering supralittoral, intertidal and subtidal zones. The bathymetric LiDAR Hawk Eye data enabled the generation of a digital elevation model (DEM) of the Oka estuary, at 2 m of horizontal spatial resolution in the terrestrial zone (with a vertical accuracy of 0.15 m) and at 4 m within the subtidal, extending a water depth of 21 m. Data gaps occurred in 14.4% of the area surveyed with the LiDAR (13.69 km²). Comparison of the LiDAR system and the MBES showed no significant mean difference in depth. However, the Root Mean Square error of the former was high (0.84 m), especially concentrated upon rocky (0.55–1.77 m) rather than in sediment bottoms (0.38–0.62 m). The potential of LiDAR topographic variables and reflectance alone for discriminating 15 intertidal and submerged habitats was low (with overall classification accuracy between 52.4 and 65.4%). In particular, reflectance retrieved for this case study has been found to be not particularly useful for classification purposes. The combination of the LiDAR-based DEM and derived topographical features with the near infrared and visible bands has permitted the mapping of 22 supralittoral, intertidal and subtidal habitats of the Oka estuary, with high overall classification accuracies of between 84.5% and 92.1%, using the maximum likelihood algorithm. The airborne bathymetric Hawk Eye LiDAR, although somewhat limited by water turbidity and wave breaking, provides unique height information obscured from topographic LiDAR and acoustic systems, together with an improvement of the habitat mapping reliability in the complex and dynamic coastal fringe.  相似文献   

Quantifying 20th century deposition in complex estuarine environment: An example from the Hudson River     

F.O. Nitsche  T.C. Kenna  M. Haberman 《Estuarine, Coastal and Shelf Science》2010

Sediment processes in estuaries are controlled by the interaction of factors that include tides, fresh water inputs, bed morphology, sediment supply, and hydrodynamics. The interaction of these factors strongly influences the pattern of sediment deposition. The ability to quantify sediment deposition on a regional scale will improve the understanding of the underlying processes, and provide valuable information for managing estuarine systems. This paper describes our approach for obtaining the deposition pattern and quantifying the amount of 20th century impacted sediments in the Haverstraw Bay section of the Hudson River Estuary. Through the combination of high-resolution seismic data and rapidly acquired geochemical information from numerous sediment cores, we estimate that our study site experiences an average sediment accumulation rate of ∼3 mm/y and that ∼75,000 t/y or ∼10% of the annual total sediment input measured at the Poughkeepsie, NY gauging station (USGS) is stored in this reach of the Hudson River on ∼100 y timescales. A detailed analysis of the depositional pattern indicates that the accumulation rate varies considerably throughout the study area ranging from non-depositional to >8 mm/y. Our data also clearly indicate that the dredged channel in Haverstraw Bay is currently the main focus of deposition in this area.  相似文献