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以长江口南支河段为研究区,利用LandsatETM+遥感影像反演的1999年水下地形和该河段2002年实测水深数据,结合长江口来水来沙现状和河段特征,分析了河段的冲淤变化和沙体迁移规律,提出了需采取的治理措施。研究结果表明:(1)从1999到2002年南支河段总体发生冲刷,年平均冲刷量为0.1926亿m3,河道内白茆沙、新浏河沙和新浏河沙包的沙头年平均后退467,374和421m;(2)上、下扁担沙之间由于串沟发育,两者有分离的趋势,沙体5m等深线的变动格局显示两沙体沙尾向下移动导致新桥水道上段水深加深、下段南侧水深变浅;(3)固定白茆沙和上、下扁担沙沙体,对维持南支河段航道的航运、稳定南北槽河势具有重要作用。 相似文献
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钱塘江河口段长周期泥沙冲淤和河床变形 总被引：2，自引：0，他引：2
通过对钱塘江河口段50多年连续水下地形资料的整理和分析,给出了该河口段在遭遇连续丰、枯水文年时的长周期泥沙冲淤特点,以及相应塑造的顺直、弯曲两种河势在河床形态与演变上的差异。研究结果认为,长周期泥沙冲淤和河床变形是钱塘江河口段保持冲淤平衡的一种自动调整手段;与冲积河流不同的是,钱塘江河口段通过河型、比降、断面等因素的调整来改变进入该河口段潮流量的大小。 相似文献
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长江口南港底沙输移及其对南、北槽分汊口的影响 总被引：7，自引：1，他引：7
以1958年以来浏河口至横沙水文站之间南港系列水下地形图数字化分析资料为基础，以成形活动沙洲和隐形活动沙包作为底沙推移的判别标志，研究底沙输移规律，底沙输移对南港河槽分化和南、北槽分汊演变趋势的影响。研究结果表明长江口底沙活动范围向口门地区推移，底沙绝大部分进入南槽。 相似文献
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海底地形地貌研究可以揭示海底表面形态特征，探索海底物质结构及其形成、演化和分布规律。通过单波束测深、单道地震、海底表层沉积物取样和潮汐水文水动力实测等方法，开展了宣德环礁水文要素和水动力条件定量化研究，对宣德环礁水下沙洲动力地貌特征及动力作用下形成机制进行了探讨。研究结果表明：宣德环礁潟湖内水深50～55 m及60 m发育的礁滩体和埋藏珊瑚礁，与全新世50～60 m的低海平面时期发育的系列特征地貌应为同时期形成，水深50～55 m处的地貌边界很可能保留了早全新世时期古潟湖礁盘地貌轮廓形态；宣德环礁潟湖发育5类动力地貌特征形态的水下沙洲，环礁底层涨落潮流是塑造水下沙洲的主要现代动力因素。在常态天气下，涨落潮流输运的砂质沉积物足以在原有地形的基础上沉积和发育形成现今水下沙洲地貌形态。影响水下沙洲发育的主要因素由强至弱依次为气候变化引起的海平面升降，地形基础（珊瑚礁格架、礁盘岸线、口门）和涨落潮流。 相似文献
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长江口新生沙洲底栖动物群落组成及多样性特征 总被引：22，自引：3，他引：22
沙洲岛屿是河口生态系统的重要组成部分,是河口海岸带资源开发、自然保护及全球变化研究的重要对象.沙洲岛屿潮滩的底栖动物群落与其生活的底质构成了河口生态系统的底栖亚系统,是河口地区生物多样性最直接和最易于观察研究的一个层次,它们在揭示群落与环境变化的关系上具有重要的作用[1-2].九段沙是长江口现代发育过程中产生的一个新生沙洲,是继崇明岛、长兴岛和横沙岛之后的又一成陆冲积沙洲,是一块重要的河口沙洲型滨海湿地[3].九段沙受人类干扰较少,其生物资源保持着天然状态. 相似文献
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黄河三角洲孤东及新滩海岸侵蚀机制研究 总被引：9，自引：0，他引：9
黄河三角洲孤东及新滩地区是黄河1976年以来清水沟流路河口新淤积的滩涂地带。根据孤东及新滩海域1997—2003年16个海岸剖面的实测地形资料以及利津水文站的水沙资料，阐述了黄河口尾闻改道清8出汉后，孤东及新潍海岸剖面的冲淤演变过程，并从动力地貌的角度对其冲淤过程和机制做了重点研究．结果表明，1998年以后，除新口门附近轻微淤积，其它岸段均遭到不同程度的侵蚀．清水沟老河口附近剖面表现为上冲下淤的侵蚀类型；其余侵蚀剖面形态则表现为均衡侵蚀型．近年来黄河入海水沙量的减少以及1996年河口流路的改变，调整了入海水沙、海洋动力和海岸地形之间的动态平衡，海洋动力相对增强，从而导致海岸侵蚀后退。 相似文献
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从水沙条件及河床地形变化规律谈长江河口综合治理开发战略问题 总被引：2，自引：0，他引：2
长江河口位于长江三角洲的核心部位，由于区域高强度的城市化，对水运工程及沿岸工程在长江口水土资源的合理开发利用中提出了更高的要求，由于长江口属典型的沙岛型中等潮汐多级分汉河口，入海汊道冲淤多变，洲滩迁移频繁，泥沙运动复杂，径流潮流相互作用及盐水洪水交汇引起流场、河势变化及河床冲淤部位极不稳定。从流域来水来沙条件变化及河口河床演变规律阐明长江口治理开发的迫切性、复杂性和综合性。 相似文献
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沙洲并陆与长江口北部岸线的演变 总被引：4，自引：0，他引：4
全新世以来，长江口北岸南通－扬州南部经历了“浅海－陆地”的成陆过程。4ka，B.P．前，本区为一漏斗形的浅水海湾，河口拦门沙极为发育.4ka.B.P。以来，沙洲并岸，河口陆地淤长，长江口北部岸线呈东南延伸之势。 相似文献
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现行黄河口滨海区冲淤时空演变及其影响因素 总被引：1，自引：0，他引：1
自黄河入海流路人工改道清 8 汊后，受自然因素变化和人类活动干预影响，入海水沙出现新的情势，河口滨海区水下地形也发生相应调整。本文基于 1997—2018 年实测水深断面资料，建立水下地形数字高程模型 （DEM），综合研究了黄河
口滨海区冲淤的时空演变及其影响因素。结果表明，1997—2018 年黄河口滨海区整体呈淤积状态，累积淤积量为 5.36 * 108 m3。从时间上来看，水下地形演变经历 3 个阶段：缓慢冲刷 （1997—2002 年）、快速淤积 （2002—2007 年）、缓慢淤积 （2007— 2018 年）。从空间上来看，现行河口区呈淤积状态，而孤东近岸和老河口区呈冲刷状态。在水下地形不同的发展阶段，维持冲淤平衡的临界输沙量也有所不同，调水调沙之前为 1.65*108t/a，调水调沙以来为 1.09* 108t/a。来水来沙对河口滨海区的冲淤演变起着主导作用，2016—2017 年调水调沙中断，河口滨海区大面积冲刷。2018 年防洪调度的实施使水下地形迅速淤积。黄河口滨海区演变除了受来水来沙的直接影响，还受泥沙粒径和口门位置的影响。 相似文献
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ＡｓｔｕｄｙｏｎｂｅｎｔｈｉｃｃｏｍｍｕｎｉｔｙｓｔｒｕｃｔｕｒｅｉｎｗｅｓｔｏｆｔｈｅＴａｉｗａｎＳｔｒａｉｔａｎｄｎｅａｒｔｈｅＴａｉｗａｎＳｈｏａｌｓ￥ＷｕＱｉｑｕａｎ；ＪｉａｎｇＪｉｎｘｉａｎｇ；ＸｕＨｕｉｚｈｏｕ；ＣａｉＥｒｘｉａｎｄＬｉｎ... 相似文献
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简要介绍了长江下游“三沙”航道整治工程中为了掌握双锏沙横流和如皋沙中汊在刘海沙水道的汇流情况,在福姜沙左汊道→双锏沙→浏海沙水道间进行了表面流速流向观测,并对测量成果和航迹线图进行了初步分析,从而为保持双锏沙的稳定、保证如皋沙群水道的长久贯通提出了一些工程措施。 相似文献
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David E. Avery Jack Green Edward G. Durbin 《Deep Sea Research Part II: Topical Studies in Oceanography》1996,43(7-8)
In this study, long-term, broad-scale zooplankton survey data were used to estimate the temporal and spatial distribution and abundance of gammarid amphipods present in the water column on Georges Bank. Delta-mean abundances computed from 10 years of data showed that gammarid amphipod abundances peaked in summer and again in fall. The amphipods were also most numerous in water less than 50 m deep. The statistical tests employed revealed no conclusive evidence for diurnal vertical migration. Interannual delta-mean abundances fluctuated approximately 5-fold between 1977 and 1986, ranging from 217 to 1181 amphipods 100 m−3. Peak amphipod biomass occurred in July and was estimated to be 2.8 kcal m−2. Using production-to-biomass ratios from the literature, mean annual production of amphipods in these samples was estimated to be between 1.6 and 9.8 kcal m−2. Production in shallow areas was especially high, 22 kcal m−2 year−1. 相似文献
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Late Holocene chronology,origin, and evolution of the St. Bernard Shoals,Northern Gulf of Mexico,USA
Several shore-parallel marine sand bodies lie on the Louisiana continental shelf. They are Trinity Shoal, Ship Shoal, Outer
Shoal, and the St. Bernard Shoals. These shoals mark the submerged positions of ancient shorelines associated with abandoned
deltas. Three of these shoals are single elongate deposits. The fourth shoal, the St. Bernard Shoals, consists of a group
of discrete sand bodies ranging in size from 44 to 0.05 km2, 25 km southeast of the Chandeleur Islands in 15–18 m of water. The St. Bernard Shoals are stratigraphically above the St.
Bernard delta complex, which was active 2,500–1,800 years b.p. Understanding the evolution of the St. Bernard Shoals is necessary to reconstruct the Holocene chronology of the St. Bernard
delta complex and the eastern Louisiana continental shelf. For this study, 47 vibracores and 400 km of shallow seismic reflection
data collected in 1987 across the Louisiana shelf were analyzed. In June 2008, 384 km of higher-resolution seismic reflection
data were acquired across the study area and appended to the preexisting datasets. Vibracores were integrated with seismic
profiles to identify facies and their regional distribution. Our results demonstrate that the deltaic package stratigraphically
below the St. Bernard Shoals is chronologically younger than the northern distributaries, but derived from the same trunk
distributary channel (Bayou la Loutre). The river eventually bypassed the northern distributaries, and began to deposit sediment
further onto the continental shelf. After abandonment, the overextended delta lobe was rapidly transgressed, creating a transgressive
shoreline that eventually coalesced with earlier shorelines in the region to form the Chandeleur Islands. The St. Bernard
Shoals formed by the reworking of the relict distributary deposits exposed on the inner to mid shelf during and subsequent
to shoreface ravinement. 相似文献
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The distribution and character of small-scale and mesoscale bedforms on the surface of a large tide-built sand ridge have
been observed. Sand waves, class 1 and class 2 megaripples, and ripples are abundant. A histogram of bedform spacing is strongly
bimodal, indicating that megaripples and sand waves comprise discrete populations. Ripples probably also comprise a discrete
population, but the limit of resolution of the side-scan sonar system arbitrarily truncates the distribution; hence a third
mode cannot be observed. 相似文献
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Biological invasion has received considerable attention recently because of increasing impacts on local ecosystems. Expansion of Spartina alterniflora, a non-native species, on the intertidal mudflats of Jiuduansha Shoals at the Yangtze River Estuary is a prime example of a spatially-structured invasion in a relatively simple habitat, for which strategic control efforts can be modeled and applied. Here, we developed a Cellular Automata (CA) model, in conjunction with Remote Sensing and Geographical Information Systems, to simulate the expanding process of S. alterniflora for a period of 8 years after being introduced to the new shoals, and to study the interactions between spatial pattern and ecosystem processes for the saltmarsh vegetation. The results showed that the CA model could simulate the population dynamics of S. alterniflora and Phragmites australis on the Jiuduansha Shoals successfully. The results strongly support the hypothesis of space pre-emption as well as range expansion with simple advancing wave fronts for these two species. In the Yangtze River Estuary, the native species P. australis shares the same niche with the exotic species S. alterniflora. However, the range expansion rate of P. australis was much slower than that of S. alterniflora. With the accretion of the Jiuduansha Shoals due to the large quantity of sediments deposited by the Yangtze River, a rapid range expansion of S. alterniflora is predicted to last for a long period into future. This study indicated the potential for this approach to provide valuable insights into population and community ecology of invasive species, which could be very important for wetland biodiversity conservation and resource management in the Yangtze River Estuary and other such impacted areas. 相似文献
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The analysis of the structure of the cryolithozone, facies, and thicknesses of the Quaternary sediments and the results of the physicochemical mathematical modeling of the modern shelf of the western part of the Laptev Sea support the influence of the Late Pleistocene glaciations on the heat conditions and the distribution of the permafrost in the area. A ～200-m thick glacier formed under aerial conditions from atmospheric precipitation represented the metamorphosed snow cover. According to the modeling, the long-living (from 60?50 to 10?4 ky) glacier reduced the thickness of the permafrost rocks in the reviewed shelf area for 280–360 m. The Holocene marine transgression additionally decreased the thickness from 50–140 m on the inner shelf to 220–350 m on the outer shelf. The modern submarine cryolithozone 450-0 m thick is wide-spread in the studied region from the coast to the shelf boundary (isobaths of 130–140 m), where it pinches out at a distance of ～380 km from the coast at a depth of ～250 m above the sea level. 相似文献
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We analyze the components of the carbon system of the Sevastopol bay waters and the balance of main sediment-forming substances
using the data of field investigations in 1998–2008. The interannual variations of total inorganic carbon and the equilibrium
partial pressure of carbon dioxide in the bay water are noted. An increase in the flux of carbon dioxide into the bay and
in the content of organic carbon in bottom sediments is revealed, and an explanation of this phenomenon is given. The priority
accumulation of organic carbon in the sediments of the bay is established. We assess the interannual variation in the relative
abundances of organic and inorganic carbon as an index of the carbon cycle stability. 相似文献