沉积过程分形表达及其冲淤幅度分析应用   总被引：2，自引：1，他引：1  

李炎  陈锡土  夏小明  李伯根 《海洋与湖沼》2000,31(1):84-92

根据１９８２－１９９５年在浙江沿岸椒江口、杭州湾、象山县大目涂取得的沉积柱样层序数据系列和重复沉积界面测量序列,利用分形理论进行沉积过程及冲淤幅度的分析。沉积过程和沉积地层层序存在自相似结构,两者之间在无特征尺度区存在着初始值以及分数维的传递。椒江河口和杭州湾南侧潮汐通道边坡沉积柱样泥层工的分数维在１．２－１．５之间。按潮汐沉积基本单元形成的时间为大小潮周期计算,沉积过程１年重现期的高程均方变幅为  相似文献   

The influence of lithology on surface water sources          下载免费PDF全文

Lydia B. Nickolas  Catalina Segura  J. Renée Brooks 《水文研究》2017,31(10):1913-1925

Understanding the temporal and spatial variability of water sources within a basin is vital to our ability to interpret hydrologic controls on biogeochemical processes and to manage water resources. Water stable isotopes can be used as a tool to determine geographic and seasonal sources of water at the basin scale. Previous studies in the Coastal Range of Oregon reported that the variation in the isotopic signatures of surface water did not conform to the commonly observed “elevation effect,” which exhibits a trend of increasing isotopic depletion with rising elevation. The primary purpose of this research is to investigate the mechanisms governing seasonal and spatial variations in the isotopic signature of surface waters within the Marys River Basin, located in the leeward side of the Oregon Coastal Range. Surface water and precipitation samples were collected every 2–3 weeks for isotopic analysis for 1 year. Our results confirmed the lack of elevational variation of surface water isotopes within this leeward basin. Although we find elevational variation in precipitation in the eastern portion of the watershed, this elevation effect is counteracted by rainout with distance from the Pacific coast. In addition, we found significant variation in surface water isotope values between catchments underlain predominantly by basalt or sandstone. The degree of separation was strongest during the summer when low flows reflect deeper groundwater sources. This indicates that baseflow within streams drained by each lithology is being supplied from two distinctly separate water sources. In addition, the flow of the Marys River is dominated by water originating from the sandstone water source, particularly during the low‐flow summer months. We interpreted that the difference in water source results from sandstone catchments having highly fractured geology or locally tipping to the east facilitating cross‐basin water exchange from the windward to the leeward side of the Coast Range. Our results challenge topographic derived watershed boundaries in permeable sedimentary rocks; highlighting the overwhelming importance of underlying geology.  相似文献   

华南沿海全新世沙坝及其改造利用   总被引：2，自引：0，他引：2  

李平日 《地理学报》1990,45(4):467-474

华南沿海沙坝为中、晚全新世形成，分为六个形成期。分析了沙坝的粒度和沉积 寺征及其分布规律。提出华南全新世沙坝的形成与砂源丰富、波浪较强、海平面已与现今相近、 勾造运动相对稳定、季风气候等条件有密切关系。认为沙坝对环境的主要不良影响是：1．产 上风沙灾害；2．烂湾坝阻塞或淤浅航遭。为此提出营造针阔叶混交防风林及配种草本、灌木 向意见。这些沙坝的主要有利因素是：且．含丰富的砂矿：2．形成漏湖式港湾；3．提烘发展农 木牧渔业的广阔空间；咯．可作为建设经济特区。沿海开发区和发展海滨旅游的土地资源。  相似文献   

Distribution and composition of phytoplankton in northeastern coastal waters of the United States     

Harold G. Marshall  Myra S. Cohn 《Estuarine, Coastal and Shelf Science》1983,17(2):119-131

Results are given from collections made during eight cruises over the northeastern continental shelf. Seasonal phytoplankton assemblages are noted, which include a variety of ultraplankton components. Areas of greatest cell concentrations were at near shore stations, Georges Bank, and at scattered sites over the shelf. Dominant species included Skeletonema costatum, Asterionella glacialis and Leptocylindrus danicus.  相似文献   

Characteristics of resuspended sediment from Georges Bank collected with a sediment trap     

C.M. Parmenter  M.H. Bothner  B. Butman 《Estuarine, Coastal and Shelf Science》1983,17(5):521-533

A sediment trap was deployed 3 m from the bottom at a water depth of 62 m on the southern flank of Georges Bank (41°02·2′N, 67°33·5′W) from 30 September 1978 to 10 March 1979 to qualitatively determine the size of sediments resuspended from the bottom by winter storms and to determine if seasonal changes in the phytoplankton could be observed in the trapped sediment.Bulk X-ray analyses of the trapped sediment showed layers of distinctly different textures preserved in the collection vessel. The median grain size of sampled layers ranged from 2·7 to 6·5 φ (fine sand to silt), but all layers contained a pronounced mode in the 3 φ (fine sand) range. Nine layers containing relatively large amounts of sand were present. The sand content was 75% in the coarest layers and about 32% in the fine layers. The median grain size of bottom sediments at the deployment site was considerably coarser than the trap samples, although the dominant grain size was also 3 φ.Average bottom-current speeds during the deployment period were about 30 cm s^?1 with a range of 10 to 50 cm s^?1. Bottom stress, computed from the observed currents and waves, suggest that 11 storms caused sufficient stress to resuspend 3 φ-sized sediments, in good agreement with the nine layers of relatively coarse sediments collected in the trap. Surface waves had to be included in the calculation of bottom stress because the bottom currents alone were insufficient to cause the resuspension of 3 φ-sized sediment.The trapped sediments contain numerous diatoms and coccoliths that are typical of late fall and winter assemblages. No clear seasonal difference in the flora was noted among sampled layers, probably due to the large influx of resuspended material and a reduced primary flux during this period. An undescribed species of Thalassiosira (G. Fryxell, personal communication), and siliceous scales of unknown systematic position were observed at all levels.  相似文献   

The dynamics of a bathymetrically arrested estuarine front     

Linda M. Huzzey 《Estuarine, Coastal and Shelf Science》1982,15(5):537-552

The mixing and circulation associated with a bathymetrically arrested estuarine front was studied using hydrographic and current data. A quasisteady front, exhibiting strongly convergent surface flows, is formed along the steeply sloping inner margins of the flood tide delta during each semidiurnal tide cycle. This front separates the brackish ambient water within a deep estuarine basin from the incoming oceanic tidal water. The position of the front is dependent on the local water depth and the difference in density between the two water masses. Beneath the surface there is an inclined frontal interface where static stability is very low and vertical mixing intense. A vertically integrated horizontal momentum equation was derived for flow in the upper layer and an estimate made as to the value of the associated entrainment coefficient.  相似文献   

Multi-tracer assessment of seasonal water source changes in coastal water systems along the southeastern coast of Ivory Coast (West Africa)     

Isimemen Osemwegie  Christine Stumpp  Jean Biemi  Barbara Reichert 《水文科学杂志》2013,58(15-16):2124-2145

ABSTRACT

Proper management of coastal freshwater resources depends on an understanding of processes controlling their chemistry and seasonal flowpaths. A quantitative approach involving the coupling of major solutes and isotopes (δ¹⁸O, δ²H) of 180 samples in end-member mixing analysis (EMMA) was adopted to elucidate seasonal patterns of hydraulic exchanges amongst coastal waters along the Ebrié Lagoon catchment, Ivory Coast. The results show that the Ebrié Lagoon is a hydrologically dynamic system. In the dry season, evaporation and seawater inflow are the dominating processes, while in the wet season, river discharge is the main water source in the lagoon. Regional geology plays a significant role in aquifer recharge patterns. The Quaternary aquifer responds faster to precipitation, while the Mio-Pliocene aquifer is recharged indirectly via floodplain seepages. Salinization of over 90% of wells arises from hydrological exchanges with the Ebrié Lagoon. A diluted seawater effect was recorded in wells during the wet season owing to the relative increase in freshwater inflow.  相似文献   

Crafting Regional Cultural Production: emergence,crisis and consolidation in the Gold Coast surfboard industry   总被引：1，自引：0，他引：1  

Andrew Warren 《The Australian geographer》2013,44(4):365-381

Surfboard-making is concentrated in regions with vibrant surfing subcultures, suitable waves and sufficient expertise in crafting boards, by hand, to suit prevailing coastal conditions. This article charts the rise of the Gold Coast as Australia's most concentrated cluster of surfboard-making, from its origins as do-it-yourself craft in backyards and sheds, to professional, export-oriented industry. Out of highly informal, subcultural origins, a regional cluster emerged in the 1960s, fuelled by the growth of surfing, tourism and suburban development, and by the needs of surfers for customised boards that suit their body size, surfing style and local wave conditions. What transpired was a vernacular form of coastal creative industry combining craft skills, subcultural knowledge and design flair. Nevertheless, a mix of factors, including automation, increased competition from cheap imports, increasingly aggressive retail trade, and mistrust among board-makers, has threatened viability. Some workshops overextended into export production, marketing and automation, and consequently suffered from exposure to risk (as well as a commensurate decline in regional tourism). Others survived, and in some ways turned full circle: those small workshops continuing to service local markets, within their means, were most able to ride out the industry's turbulent times. Small-scale cultural production persists despite the volatility of the larger brands, geared instead around loyal customers who want hand-crafted boards made by shapers who they know and trust.  相似文献   

Rethinking Precolonial Plant Cultivation on the Northwest Coast of North America     

《The Professional geographer》2013,65(2):140-157

The indigenous peoples of the Northwest Coast of North America are widely believed to have been true “hunter-fisher-gatherers,” lacking plant cultivation of any kind. This depiction of the region's indigenous inhabitants emerged within early colonial accounts and was perpetuated within the literatures of geography, anthropology, and archaeology. Still, there is ample evidence of plant cultivation available from archival, archaeological, and ethnographic sources. In particular, the peoples of coastal British Columbia created large gardens of edible estuarine plants, using sophisticated indigenous technologies. The oversight of these practices in written representations of the region reveals consistent patterns of bias, emanating from the agendas of colonial agents and early academics alike. In turn, this bias has undermined aboriginal traditions of cultivation and indigenous land claims.  相似文献   

区位和管理政策对海岸带土地利用变化的影响--以昌黎黄金海岸地区为例   总被引：11，自引：3，他引：8  

王敬贵  苏奋振  周成虎  杨晓梅  杜云艳  陈秀法 《地理研究》2005,24(4):520-526

本文在RS和GIS支持下研究了河北昌黎黄金海岸地区1985年至2000年的土地利用变化格局及其影响因子。该区域的海岸区位对海岸带土地利用变化具有重要影响作用,近岸带变化较剧烈,远岸带变化较小,且具有不同的变化特点。海岸带管理政策对土地利用变化的程度和特征存在重要影响,开发区土地利用变化较剧烈,其变化类型受开发方式及其目标影响;保护区主要是大片沙丘转变为林地和草地。  相似文献