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1.
防护丁坝抗冲刷失效安全可靠性分析 总被引：1，自引：1，他引：0
分析了防护丁坝冲刷的机理,用概率分析方法研究了在随机因素影响下防护丁坝抗冲刷的可靠性问题.应用Rosen-blatt变换确定防护丁坝抗冲刷破坏的功能函数在随机因素影响下的可靠性指标.提出了用丁坝端部冲刷坑的当量坡度小于冲刷坑坡度的临界值JD作为丁坝抗冲刷破坏的安全（稳定性）准则.分别考虑了水道流速、土颗粒等效直径、冲刷坑半径、冲刷坑后坡度临界值和水流方向角为相关或独立的非高斯随机参数时的可靠性问题.该分析能为防护丁坝系统的抗冲刷可靠性评估和设计提供有实用价值的方法. 相似文献
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在航道治理工程中,往往通过丁坝群来实现其稳定航槽等目的,而坝田作为缓流区,其与主槽的水沙交换主要取决于横向的紊动交换。基于长江口北槽丁坝群实测资料分析和物理模型水槽试验研究发现不同长宽比坝田内的流态、淤积形态、坝田与相邻河段水沙交换的机理均不同,在长江口北槽丁坝群坝田建成后的淤积初期阶段,长宽比为0.30～0.40的坝田内的平均淤积强度最大。水槽试验研究表明,长宽比为0.50的坝田内淤积的主要部位即为主环流所在位置(坝田外侧),而在副环流位置,则出现微淤或冲刷的趋势;而长宽比为0.33的坝田内的淤积分布相对比较均匀。长宽比为0.33的坝田内淤积速率明显大于长宽比为0.50的坝田,长宽比为0.33的坝田达到冲淤平衡的时间较长。坝田淤积强度与随坝田回流强度、坝田与主槽水沙交换系数的增加而增加。 相似文献
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The south-western shoreline along the entrance channel inside the Port of Richards Bay has experienced continued erosion. Four groynes were constructed to stabilise the shoreline. Monitoring of shoreline evolution provided valuable data on the accretion adjacent to two of the groynes and on the sediment transport rates at these groynes. Tides, beach slopes, winds, wave climate, current regime, and sand grain sizes were documented. The one site is “moderately protected” from wave action while the other is “protected” according to the Wiegel [Wiegel, R. L. (1964). Oceanographical engineering. Prentice Hall, Inc., Englewood Cliffs, NJ.] classification. The shoreline accreted progressively at the two groynes at 0.065 m/day and 0.021 m/day respectively. The shorelines accreted right up to the most seaward extremity of the groynes. Equilibrium shorelines were reached within about 3.5 years to 4 years, which compare well with other sites around the world. The mean wave incidence angle is large and was found to be about 22°. The median sand grain sizes were 0.33 mm and 0.37 mm. The groynes acted as total traps, the beach surveys were extended to an adequate depth, and cross-shore sediment transport did not cause appreciable net sand losses into the entrance channel. The net longshore transport rate along the study area, which is north-westbound, is only slightly lower than the gross longshore transport. The actual net longshore transport rates are 18 000 m3/year and 4 600 m3/year respectively at the two groynes. A rocky area limits the availability of sand at one groyne. There is fair agreement between the predicted and measured longshore transport rates at the other groyne. 相似文献
4.
Anthropogenic factors and habitat complexity influence biodiversity but wave exposure drives species turnover of a subtropical rocky inter‐tidal metacommunity 
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下载免费PDF全文 Coastal ecosystems are complex and species rich, but are vulnerable to degradation from a variety of anthropogenic activities. Nevertheless, information on inter‐tidal community composition in the Caribbean Basin and at other oceanic sites is lacking. Such information is essential to developing a more comprehensive understanding of rocky inter‐tidal systems and their responses to global change. The goals of this study were to determine the relative importance of environmental (wave power density, wave height), habitat (e.g. algal cover, slope, complexity of rock surfaces) and anthropogenic (distance to roads, population density) factors associated with the structure of local assemblages at multiple shore heights and the regional metacommunity of mobile invertebrates on oceanic rocky inter‐tidal habitats. Environmental characteristics associated with habitat complexity (algal cover, rock surface complexity) and human population density were most strongly associated with abundance and biodiversity of invertebrates. Species richness was positively correlated with surface complexity, but abundance was negatively correlated with both surface complexity and per cent algal cover. By contrast, abundance of invertebrates was positively correlated with human population density, and diversity was negatively correlated with human population density. Abundance of invertebrates was greatest in the mid inter‐tidal zone, whereas diversity was greatest in the lower inter‐tidal zone. Metacommunity structure was Gleasonian, but the gradient along which species turnover occurred was correlated with measures of wave exposure, rather than anthropogenic activity. Unlike in previous studies, mostly at mainland sites, human activity primarily altered dominance patterns of communities, while having relatively little effect on species richness or composition. 相似文献
5.
本文对福清湾北部及其以东近岸海域的地质地貌，潮流和波浪等沉积环境因素，以及对沉积物和悬浮泥沙的粒度，矿物特征进行研究，认为福清湾为溺谷型的半封闭潮汐汊道海湾存在着较大的潮差和潮流流速，沉积物沿潮流方向呈东粗西细和岸边细、向海变粗的潮流分异特征，潮流控制着沉积物的布局，而属于潮控的浅海沉积环境。 相似文献
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南麂列岛海洋自然保护区潮间带软体动物生态研究 总被引：5，自引：1，他引：5
本研究结果表明，共鉴定出软体动物１４３种，其中１８种为该区域首次记录。根据种类相似性指数，将其分成５个生态群落：即开敞岩礁群落，隐蔽岩礁群落，巨砾群落，泥滩群落，沙滩群落。文中对各群落的种类组成、数量分布、季节变化及多样性指数等作了分析；同时对影响软体动物生态分布的潮汐、波浪、底质类型和生物因子等作了探讨。 相似文献
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于１９８８年９月－１９８９年１月在大亚湾潮间带采集底栖动物标本，经分类研究发现，共有５４７种，其中藻类９１种，多毛类１２０种，软体动物２０９种，甲壳动物８３种，棘皮动物１９种，其他动物２５种。研究表明，其区系性质以热带亚热带暖水种占多数，有许多热带种发展成优势种。在水平分布上，岩石相种类（３１６）＞沙滩种数（２２２）＞红树林泥滩（５１）；在垂直分布上，中潮区种数（３９８）＞低潮区（２２１）＞红树林 相似文献
9.
Spatial variability of intertidal rocky shore assemblages in the northwest coast of Portugal 总被引：1，自引：0，他引：1
R. Araújo I. Brbara I. Sousa-Pinto V. Quintino 《Estuarine, Coastal and Shelf Science》2005,64(4):658-670
The spatial variability of rocky shore assemblages of the northwest Portuguese coast was studied in a total of 12 transects, visited twice between March and August 2003. Each transect was positioned from the upper to the lower shore and four replicate samples (50 × 50 cm) were taken at each visually identified assemblage. Multivariate analysis was used to test the null hypothesis of no significant differences among assemblages located on different heights along the transect and among assemblages located at the same height on different transects. The distribution pattern of organisms along the height was not consistent across transects and significant variability could be found in assemblages located at the same height on the shore. Globally, the variability from the lower to the upper shore (vertical axis) was larger than from transect to transect (horizontal axis) but the distribution pattern along height was clearer in sheltered transects than in exposed ones. The heterogeneity in composition between the visually identified assemblages, within the same transect, was, however, the major source of variability in the study area. In the rocky intertidal northwest coast of Portugal, where tidal amplitude is broad and extremely wave-exposed sites are scarce, height above chart datum was the most important factor determining the distribution and species composition of the assemblages. However, variability along the horizontal axis was also significant and should be considered in studies of spatial patterns of distribution of organisms within this area. 相似文献
10.
Localized versus regional adaptation in limpet shell morphology across the Iberian Peninsula 下载免费PDF全文
下载免费PDF全文 Hunter N. Hines Hannah Morriss Karen Saunders Rachel L. Williams Sarah L. Young Richard Stafford 《Marine Ecology》2017,38(6)
The climate‐envelope approach to predicting climate‐induced species range shift is limited. There are many possible reasons for this, but one novel explanation is that species adapt to changes in temperature at the expense of adaptation to other stressors. Here we test this hypothesis using the limpet Patella depressa (Mollusca, Patellidae), over a large geographical area covering most of the Atlantic coast of the Iberian Peninsula, known to consist of a genetically inter‐connected population. We examine limpet shell morphology on four shores in each of three regions, from Northern Spain to Southern Portugal. Within each region, shell morphology (measured as maximum shell profile to length ratio) varied between shore types differing in their insolation, wave action, microhabitat availability and biological factors. However, this ratio, which is known to be an adaptive response to heat stress, was found to be consistently higher in more southern latitudes despite differences between shore types being found in all regions. This implies that localized adaptation to shore type (most likely through phenotypic plasticity) is compromised by factors that change over latitudinal or regional scales, or which could occur in response to climate change. Although such climate‐induced changes may initially be localized, compromised adaptation (through phenotypic or genetic plasticity) may result in altered community interactions and potentially large shifts in community structure. 相似文献
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Alan L. Shanks 《Marine Ecology》2011,32(2):232-242
Sandy beach/surf‐zone ecosystems are unique environments that, despite the harsh and highly variable hydrodynamic conditions, present a diverse and heterogeneous fauna. However, the dynamics of these ecosystems are currently poorly understood. In this study we tested the hypothesis that surf‐zone assemblages vary with temporal factors such as time of day, tide and tidal height. To test this hypothesis, the surf‐zone community of Bastendorff, a Southern Oregon sandy beach was sampled during the summer of 2006. Samples were collected to (i) describe the smaller, benthic and larger swimming assemblages, (ii) determine whether assemblage compositions, densities, species richness and diversity vary with time of day, tide and tidal height, (iii) explore potential reasons for the variation by correlating environmental factors to the assemblages, and (iv) identify particular species that most strongly exhibit these variations. A hyperbenthic sledge, a sediment corer and a beach seine were used to collect the smaller swimming, benthic and larger swimming fauna, respectively. Sampling occurred during day and night, spring and neap tide, and high, mid and low tide. A total of 76,743 individuals belonging to 105 species were collected. Ninety‐one invertebrate (72,904 individuals), 15 invertebrates (2234 individuals), and 19 invertebrate and vertebrate species (1605 individuals) were collected with the sledge, corer and seine, respectively. Nine species of fish were caught, 98% of which were juveniles. The smaller and larger swimming assemblages varied most strongly with the time of day, suggesting certain species will actively move to the shallow surf‐zone at night. The three assemblages also varied with the tide, potentially due to the larger waves and higher abundance of detached macrophytes observed during spring tides when compared to neap tides, which could push individuals into the surf zone. The benthic assemblage most strongly varied with tidal height and sand grain size, confirming the presence of different faunal zones within Oregon sandy beaches. Finally, several variables of the swimming assemblages varied with temperature and salinity, suggesting that downwelling favorable conditions may have transported species close to shore. Bastendorff presents a complex and diverse surf‐zone community that appears to be influenced by diel species movements, environmental variables such as wave height and abundance of detached macrophytes, and regional oceanographic conditions. 相似文献
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Tatiana F. Maria Jan Vanaverbeke Ruth Gingold André M. Esteves Ann Vanreusel 《Marine Ecology》2013,34(2):207-217
Lately, across‐shore zonation has been found to be more important in structuring the nematode community of a tropical macrotidal sandy beach than microhabitat heterogeneity. To evaluate whether this zonation pattern applies to a temperate beach, a macrotidal ridge‐and‐runnels sandy beach in the North Sea was studied. We investigated whether a similar zonation occurs in sandbar and runnel microhabitats, and whether the runnels harbour a different community from the subtidal. Our results indicate that nematode communities from runnel and sandbar habitats are significantly different. In addition, horizontal zonation patterns for nematode communities differ between both habitats. Nematode assemblages from sandbars are divided to lower, middle and upper beach while upper and middle runnels cluster together. The subtidal and upper runnels showed dissimilar nematode assemblages, although runnels showed the same dominant species (Daptonema normandicum), which increases its abundance towards the upper runnels. This study illustrates the importance of microhabitat heterogeneity, which resulted in different zonation patterns across the sandy beach examined. The divergent zonation between sandbars and runnels in the macrotidal temperate sandy beach, compared with the pattern observed for a subtropical sandy beach with similar morphodynamics, indicates that generalizations about nematode distribution patterns should be made with caution. 相似文献
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黄河三角洲孤东海域沉积物及水动力 总被引：7，自引：0，他引：7
根据黄河三角洲孤东近岸海域表层沉积物取样、水文泥沙观测和风浪资料推算,分析沉积物特征和运移趋势,并通过水动力条件(潮流和波浪)探讨沉积物起动和输移特征。结果表明,孤东海域沉积物多为粉砂类物质,由内向外逐渐变细,分选变差,丁坝的修建对周围粒径分布影响明显;沉积物运移趋势受风成余流、岸线轮廓和丁坝工程修建的影响,不同区域表现为不同的输移方向;研究区水动力表现为波浪掀沙、潮流输沙的特征,由于潮流较小,不足以引起泥沙的起动,泥沙起动主要由波浪引起。 相似文献
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Equilibrium erosion of soft rock shores with a shallow or absent beach under increased sea level rise 总被引：1，自引：0，他引：1
A process-based numerical model was used to explore the response of soft rock shores with low volume beaches to variable rates of sea level rise. Equilibrium recession rates were simulated for ranges of wave height and period, tidal amplitude, rock strength, beach volume and rate of sea level rise. Equilibrium shore profiles were found to be steeper with higher rates of sea level rise. Beaches were represented as protective surfaces yet were found to cause no significant reduction in equilibrium recession rate when their volumes were below a critical threshold. Reduced equilibrium recession rates were found with beaches that extended sufficiently far below low tide level. The model results imply that, given several constraints, a very simple relationship exists between increased rates of sea level rise and the response of eroding composite soft rock/low volume beach shores. 相似文献
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John R. Walsby 《新西兰海洋与淡水研究杂志》2013,47(2):211-238
The grazing turbinid gastropod Lunella smaragda was sampled regularly over 3.5 y from precise sites of different microtopography and height on the platform shore at Goat Island Beach near Leigh, Northland, New Zealand. Growth is linear for over 3 y, and the year‐classes distinct. The position of the different size‐classes is related to both the shelter afforded by the microtopography, and to the height on the shore. The populations in the mid‐eulittoral turf flats, low eulittoral bare rock areas, and the sublittoral fringe are distinct, and there is a general movement down the shore with age and size. Wave action apparently dislodges the animals from higher areas when they grow to a critical size and transports them to sites lower on the shore, where wave disturbance is less. Field experiments with marked animals and laboratory studies with a wave tank confirm that the wave‐effected distribution is size related. However measurements showed that the ratio of foot attachment area to the shell area presented to the wave does not vary with animal size. The possible benefits of wave dislodgment and wave‐effected distribution are considered. 相似文献
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Ray-Yeng Yang Ying-Chih Wu Hwung-Hweng Hwung Jiing-Yih Liou Igor V. Shugan 《Ocean & Coastal Management》2010,53(9):552-561
The shoreline of Taiwan is approximately 1100 km long, composed of sandy beach, rocky coast, and reef coast. Almost half of the shoreline has been protected by seawalls, which play an important role for coastal protection and prevent people and infrastructure from coastal hazard. Besides, offshore breakwaters and groynes are also built in the serious erosion coastal shores. All these hard engineering structures made our coastal land safety to some extent at last fifty years. However, until now, the hard engineering structures applied for shore protection do not always work well on all the coasts around Taiwan. Some coastal areas still get eroded seriously with structures being damaged. Furthermore in the recent years, people gradually value the shore protection from different viewpoints, like environment, recreation, and ecology. The objectives of the shore protection are diversified by these new demands.Therefore, the purpose of this study is to evaluate the strategy on how to conjoint soft solutions into the current hard engineering structures for beach erosion control throughout Taiwan coast. Meanwhile, this paper will also introduce environmentally, user-oriented, and technically sound creditable protection works to meet the new trends of shore protection. For application purpose, two local sites in the southwestern Taiwan coast are selected for field experimental study to integrate the proposed soft solution with hard shore protection system at present. Furthermore for coastal management purpose, this paper also collects and analyzes hydro-morphodynamic data around Taiwan in order to identify beach erosion mechanism. Lastly, the results are presented by database and geographic information system. 相似文献
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基于SWAN波浪传播模型建立包含风暴潮与天文潮耦合传播的台风浪数值模型,将1949年以来登陆我国大陆沿海最强的5612#台风作为典型的超强台风,计算了超强台风沿中线和北线路径登陆遭遇天文潮高潮位时产生的沿海波高过程。结果显示:河口波高总体分布下游大于上游,北岸大于南岸,两岸代表断面堤前最大有效波高可达5.5 m;中线路径生成的近岸台风浪波高为单峰过程,北线路径时北岸的波高出现双峰过程,波高峰值与风暴高潮位并非总是同步出现,两者时间差最大为4 h;根据频率曲线分析,中线、北线路径超强台风作用下乍浦站台风浪的重现期分别为135 a和350 a;中潮时的近岸台风浪波高比大潮降低0.1~0.2 m,小潮时再比中潮降低同样幅度。这些结论对海堤工程设计和防灾减灾具有重要意义。 相似文献
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《Coastal Engineering》2006,53(11):879-895
Shore erosion is currently causing millions of dollars worth of damage to shorelines and public properties not only along the east coast of Korea but also around the world. Little else needs to be said to emphasize that, without adequate protection, a very significant part of our coastline will fall prey to the ravages of the sea and to man himself. In recent years, because of the shortage of natural rock, traditional forms of river and coastal structures have become very expensive to build and maintain. Therefore, the materials used in hydraulic and coastal structures are changing from the traditional rubble and concrete systems to cheaper materials and systems. One of these alternatives employs geotextile tube technology in the construction of shore protection structures, such as groins, jetties, detached breakwaters and so on. Recently, geotextile tube technology has changed from being an alternative construction technique and, in fact, has advanced to become the most effective solution of choice.This paper presents the various issues related to the geotextile tube construction for shore protection at Young-Jin beach on the east coast of Korea. A new approach to a stability analysis by 2-dimensional limit equilibrium theory is highlighted and the hydraulic model test results and case history of Young-Jin beach projects are described. Based on the results of stability analysis and hydraulic model tests, a two line geotextile tube installed with zero water depth above crest was found to be more stable and effective for wave absorption than other design plans. Also, the shoreline at Young-Jin beach was extended by about 2.4–7.6 m seaward, and seabed sand was gradually accumulated around areas covered by the geotextile tube. 相似文献