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891.
阐述了太平洋潮波传入南海北部的途径与海底沙脊和沙波的区域分布 ;分析了各沙脊和沙波区的潮流动力环境和地貌沉积特征 ;讨论了海底沙脊和沙波发育演变问题。 相似文献
892.
Nine different types of cross‐stratified packages from the coal‐bearing, deltaic succession of the Barakar Formation (Permian) of the Satpura Gondwana Basin, central India, are described. The deposits are characterized by periodic mudstone drapes, reactivation surfaces including all other features suggestive of deposition from periodically unsteady, tidally‐influenced flows. The inferred flow patterns varied from purely bidirectional to pulsating unidirectional. The different types of cross‐stratified packages are interpreted to have resulted from superimposition of ebb‐oriented, steady, unidirectional fluvial currents of variable strength on the tidal flow in a deltaic setting. The study helps to distinguish cross‐strata that may develop in settings where fluvial and tidal currents interact. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
893.
894.
In this paper, sediment samples were collected along the Wanquan beaches and sieved in the laboratory in order to obtain the grain size distributions and associated parameters, i.e. mean grain size,sorting coefficient and skewness. Furthermore, we have calculated the longshore drift sediment transport rates and equilibrium cross-sectional areas of the entrance channel by using the method of sedimentary dynamics. The results indicate that the longshore drift sediment transport is dominated by waves with a direction from south to north, which result in rapid changes of the entrance channel.Therefore, some suggestions were proposed for improving the water quality and restoring the ecosystem of estuary. The engineering method includes increasing the sea-route of entrance channel,tidal prism and water exchanges in Shamei Lagoon. 相似文献
895.
滨浅海单波束测深潮汐改正的方法 总被引:2,自引:0,他引:2
单波束测深仪在现在的海上地质调查中被广泛应用,潮汐校正是必不可少的内容。我们给出一种利用潮汐预报值进行潮汐改正的方法和过程,并介绍该方法在黄河三角洲环境地质补充调查项目中的应用。 相似文献
896.
人类活动对苏北潮滩发育的影响 总被引:14,自引:5,他引:9
江苏北部潮滩宽阔而平坦,历史上就是人类活动比较频繁的地区。随着对潮滩开发利用强度和深度的增加,人类对潮滩发育的影响越来越显著。潮滩剖面自然发育的均衡形态为上凸型;潮滩被围垦并建堤后,改变了原有的水沙动态平衡关系,潮滩剖面形态发生了调整,海堤附近的潮水沟则不断被淤积。大米草和互花米草等植被的引种改变了潮滩生态结构,由于植被能降低水流流速和波浪能量,起到捕捉沉积物的作用,因此能增加潮间带滩面的淤积速率,改变潮滩分带结构;此外,植被的存在还影响到滩面潮水沟的形态。港口工程的建设改变了沉积物的输运方向。 相似文献
897.
898.
潮流发电水轮机基于动量定理的性能计算方法研究 总被引:2,自引:0,他引:2
以潮流发电水轮机的设计为研究背景,分析和总结了基于动量定理方法的四种流管模型(单盘面-单流管模型、双盘面-单流管模型、单盘面-多流管模型和双盘面-多流管模型)在竖轴变攻角水轮机的水动力性能计算中的应用,特别是能量利用率预报方面的应用。说明基于动量定理的模型在求竖轴变攻角潮流发电水轮机的水动力性能方面,能够预报一些定性特性和总体趋势,为水轮机的设计和计算提供一种初步方法。 相似文献
899.
Heng Wang Ping Zhang Shuai Hu Huayang Cai Linxi Fu Feng Liu Qingshu Yang 《水文研究》2020,34(13):2878-2894
Both natural changes (e.g., tidal forcing from the ocean and global sea level rise) and human-induced changes (e.g., dredging for navigation, sand excavation, and land reclamation) exert considerable influences on the long-term evolution of tidal regimes in estuaries. Evaluating the impacts of these factors on tidal-regime shifts is particularly important for the protection and management of estuarine environments. In this study, an analytical approach is developed to investigate the impacts of estuarine morphological alterations (mean water depth and width convergence length) on tidal hydrodynamics in Lingdingyang Bay, Southeast China. Based on the observed tidal levels from two tidal gauging stations along the channel, tidal wave celerity and tidal damping/amplification rate of different tidal constituents are computed using tidal amplitude and phase of tidal constituents extracted from a standard harmonic analysis. We show that the minimum mean water depth for the whole estuary occurred in 2006, whereas a shift in tidal wave celerity for the M2 tide component occurred in 2009. As such, the study period (1990–2016) could be separated into pre-human (1990–2009) and post-human (2010–2016) phases. Our results show that the damping/amplification rate and celerity of the M2 tide have increased by 31% (from 7 to 9.2 m−1) and 28% (from 7 to 9 m·s−1) respectively, as a consequence of the substantial impacts of human interventions. The proposed analytical method is subsequently applied to analyse the historical development of tidal hydrodynamics and regime shifts induced by human interventions, thus linking the evolution of estuarine morphology to the dominant tidal hydrodynamics along the channel. The observed tidal regime shift is primarily caused by channel deepening, which substantially enlarged the estuary and reduced effective bottom friction resulting in faster celerity and stronger wave amplification. Our proposed method for quantifying the impacts of human interventions on tidal regime shifts can inform evidence-based guidelines for evaluating hydraulic responses to future engineering activities. 相似文献
900.
Large seasonal changes in the recharge of seawater in a subterranean estuary revealed by a radon tracer
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Activities of radon (222Rn) in groundwater were continuously monitored in a saline aquifer from September 2010 to July 2011. The activities of 222Rn ranged from 200 to 4300 Bq m?3, with a large seasonal variation. Because the activity of 222Rn in seawater is low, 222Rn in saline groundwater must be produced in the aquifer from radium (226Ra) in rocks and sediments. The 222Rn activities were higher in the warm‐dry seasons (September–November 2010 and April–May 2011) when the saline aquifer was stable. In contrast, the lowest 222Rn activities were observed in the cold‐dry season (December 2010 and January–March 2011), because of the effective exchange between groundwater and seawater. In addition, sudden decreases of 222Rn activities coincided with episodic drops in groundwater temperatures. These results reveal that lower seawater temperature in winter may result in density‐driven seawater intrusion. During the wet season (June–July 2011), 222Rn activities were more clearly affected by semi‐monthly and diurnal tidal pumping, showing higher 222Rn activities during low and spring tides. Such a tidal effect was not clearly observed during the warm‐dry and cold‐dry seasons. This result implies that the residence time of SGD in coastal zones is significantly affected by seasonal changes in driving forces such as tidal pumping and seawater intrusion. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献