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The East Central climate division of Louisiana is used as a case study to evaluate relationships between divisional climate data and the 15 largest flood events on each of seven rivers during a 25-year period. Monthly precipitation and moisture surplus (a water-budget component) are correlated with number of rivers in flood within the division; the Palmer Drought Severity Index (PDSI) is not. Although divisional data sets index climatic variability for nearly 100 years, this study indicates that some cautions should be considered when applying divisional data to flood analyses. [Key words: water budget, PDSI, climate division data, flooding, storm precipitation.] 相似文献
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长江口瑞丰沙嘴演变分析 总被引：1，自引：0，他引：1
利用1958～2005年长江口地形图及实测水、沙资料,对瑞丰沙嘴的产生、演变过程进行了分析。研究结果表明:瑞丰沙嘴形成于20世纪50年代后期,丰富的泥沙来源使瑞丰沙嘴迅速下延扩大,南港演变为"W"型复式河槽,"外沙里泓"效应显现。2001年瑞丰沙嘴中部受冲刷分裂成上、下2个沙体。为确保长兴岛南岸工业区对长兴南小泓的水深要求,应采取措施保持瑞丰沙嘴的稳定。 相似文献
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A. M. R. Burnet 《新西兰海洋与淡水研究杂志》2013,47(1):147-151
Scales and fin rays from brown trout (Salmo trutta L.) of known age were examined. Only 6 out of 29 scales were read correctly by 2 operators. The commonest fault was to read an extra year into the first year's growth. Fin ray sections proved much easier to read than the scales. The author correctly read all of a sample of 22 fin ray sections. 相似文献
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本文从杭州湾北岸历史变迁和上海南汇新老海塘建塘史叙述了南汇嘴发育过程的间歇性特点。位于南汇嘴嘴尖的芦潮港岸滩近５０年也呈现冲淤交替的特征，且冲淤过程由东向西传递。诱发这种冲淤波动的直接原因是摇头沙的偏转，而其根源应追溯到长江口河势的变化。本文以近５０年来长江口的两个事件──北槽和江亚南泓的形成──阐述了它们对芦潮港岸滩动态的影响。 相似文献
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长江口南汇嘴潮滩短期冲淤演变及其动力机制研究 总被引：1，自引：2，他引：1
潮滩地形的冲淤演变规律可以在一定程度上反映动力作用与地貌特征之间的相互耦合机制.根据近几年在长江口南汇嘴潮间带多断面连续观测资料,探讨区域内潮间带滩地的近期冲淤演变特征及其主要影响因子.研究结果表明:(1)南汇嘴潮滩近期主要呈现淤涨态势,而且年内过程季节性差异明显;受区位差异影响,不同观测断面的潮滩冲淤演变呈现特征不尽相同,断面1冲淤变化最为显著,年最大冲淤厚度均在10cm以上;(2)在波浪、潮流的作用下,区域内沉积物很容易被掀动悬扬,而且输沙环流系统的存在有利于悬沙向浅水区输运且在该区域内沉降淤积,从而为潮滩发育提供泥沙来源;(3)受"碧利斯"台风引起的风暴潮天气影响,研究区域内潮滩出现"大冲大淤"现象,即台风强侵蚀期过后滩面高程短期内恢复明显.由此可见,潮滩短期冲淤演变特征是各种动力因素作用下的综合体现. 相似文献
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Domains of spit evolution in the Goro area, Po Delta, Italy 总被引：2，自引：0，他引：2
Goro lagoon was formed during the 19th century in the southern part of the Po Delta. Its origin is related to the growth of a spit system, which progressively occluded the southernmost interdistributary bay from the sea. The development of the spits is due to the morphological prominence of the Po Delta which causes a divergent littoral drift, enhanced by wave refraction over the delta front. During the last century the spit was abandoned, destroyed, and re-constructed several times because of the development of newer spits seawards. Using historical maps and aerial photographs, three different periods are recognised, featuring distinctive spit growth styles: parallel, fan-shaped and branched. The different domains of spit evolution are related to several factors, mainly to the mutual influence of sediment discharge, sand mining along the Po river, wave action over the delta front, human-induced subsidence and direct human interventions along the spits and for flood-control. 相似文献
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Species composition and biomass of plankton samples taken on transects across an upwelling plume off Farewell Spit in February 1981 are presented. Copepods were numerically dominant, particularly Oithona similis and Paracalanus indicus. Also abundant were large phytoplankters (Chaetoceros sp. and Trichodesmium sp.), crustacean faecal pellets, and euphausiid larvae. The distribution of zooplankton species suggests mixing of inshore waters and neritic populations with upwelled waters. These data are discussed with respect to an interpretation of the upwelling system as a northwards transport of zooplankton and its enhanced productivity into the South Taranaki Bight. 相似文献
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A mathematical model of spit growth and barrier elongation adjacent to an inlet (of arbitrary width), supplied by sediment coming from longshore sediment transport, was developed based on the spit growth model proposed by Kraus (1999). The fundamental governing equation is the conservation equation for sand, where the width of the spit is assumed constant during growth. The portion of the longshore sediment transport feeding the spit has been estimated based on the ratio between the depth of the inlet channel and the depth of active longshore transport. Sediment transport from the channel due to the inlet flow, as well as other sinks of sand (e.g., dredging), are taken into account. Measured data on spit elongation at Fire Island Inlet, United States, and at Badreveln Spit, Sweden, were used to validate the model. The simulated results agree well with the measured data at both study sites, where spit growth at Fire Island was restricted by the inlet flow and the growth at Badreveln Spit was unrestricted. The model calculation for Fire Island Inlet indicates that the dredging to maintain channel navigation is the major reason for the stable period observed from 1954 to 1994 at the Fire Island barrier. The average annual net longshore transport rate at the eastern side of the Fire Island inlet obtained in this study was about 220,000 m3/yr, of which approximately 165,000 m3/yr (75% of the net longshore transport) is deposited in the inlet feeding the spit growth, whereas the remaining portion (25%) is bypassed downdrift through the ebb shoal complex. 相似文献
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渤海南部黄河口沙嘴-刁龙嘴跨海通道建设构想 --兼议莱州湾国土资源综合整治 总被引：2，自引：0，他引：2
针对莱州湾的地理位置和周边地区的资源环境问题，根据莱州湾沉积环境演化的渴湖化趋势，提出修建以黄河口沙嘴——刁龙嘴跨海大桥(堤)为核心的莱州湾跨海通道，其一期工程是在莱州浅滩基础上修建人工半岛。同时对该工程的综合效益、投资、技术可行性、负面影响等问题进行了论证。 相似文献
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Tyre and Alexandria's coastlines are today characterised by wave-dominated tombolos, peculiar sand isthmuses that link former islands to the adjacent continent. Paradoxically, despite a long history of inquiry into spit and barrier formation, understanding of the dynamics and sedimentary history of tombolos over the Holocene timescale is poor. At Tyre and Alexandria we demonstrate that these rare coastal features are the heritage of a long history of natural morphodynamic forcing and human impacts. In 332 BC, following a protracted seven-month siege of the city, Alexander the Great's engineers cleverly exploited a shallow sublittoral sand bank to seize the island fortress; Tyre's causeway served as a prototype for Alexandria's Heptastadium built a few months later. We report stratigraphic and geomorphological data from the two sand spits, proposing a chronostratigraphic model of tombolo evolution. 相似文献
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