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1.
The cross-shore profile and the textural distribution of foreshore sediments of Ganpatipule beach along Maharashtra coast covering two annual cycles are examined. Ganpatipule beach depicts erosion and accretion of the berm, reduction and widening of foreshore widths during the monsoon (June–September) and post-monsoon (October–May), respectively with net sediment accretion during the study period due to the changes in the wave characteristics. A direct correlation is observed between the median sediment grain size and beach-face slopes signifying high wave energy ensuing to a gentle to very gentle slope. The sediments are mainly medium grain size, moderately well sorted, bimodal, very fine skewed to very coarse skewed and very platykurtic to very leptokurtic in nature. The binary plots of the textural parameters (mean, skewness, kurtosis, and standard deviation) depicted a characteristic beach environment of deposition. The study shows that the sediment is concentrated in the environment of rolling and bottom suspension. The study on grain size distribution of sediments could be used to assess the wave energy condition prevailing along the coastal area. 相似文献
2.
The foreshore of Pendine Sands forms the seaward part of an extensive, sandy coastal barrier in a shallow Carmarthen Bay, SW Wales. The sedimentological features of the macrotidal foreshore reflect a tide-induced modification of nearshore wave characteristics. As the tide ebbs, the breaker height may decrease, the surf zone widens and becomes increasingly dissipative, and swash/backwash velocities diminish. A concomitant change from plunging to spilling breakers and increasingly symmetrical swash zone flows are associated with a decreasing beach gradient.
A zero net transport model demonstrates that the beach profile is self-stabilising in the short-term, and periodic levelling has shown that the beach is in long-term equilibrium with prevailing conditions, though this does not preclude a significant dynamic response to changing tides and waves.
The flow regimes of wave-generated currents decline as the tide ebbs, and normal beach processes do not usually affect the lower foreshore. Accordingly, there is an overall seaward-fining of the primary framework component of the sands. In more detail, this framework component displays a slight seaward-coarsening across an upper foreshore dominated by high water swash and surf; a rapid seaward-fining across the mid-foreshore in response to the ebb-attenuating swash zone flow velocities; and a slight seaward-fining across the lower foreshore under the action of nearshore shoaling waves. Bedforms vary from a swash/backwash emplaced flat bed across the upper foreshore to the small ripples of nearshore asymmetric oscillatory flows across the lower foreshore.
The surface sediment veneer is not representative of the subsurface sediments which form in response partly to fairweather conditions, partly to storms. The upper foreshore is characterised by swash/backwash emplaced plane bedding in fine sands frequently disrupted by bubble cavities. The mid-foreshore is composed of coarser-grained shelly traction clogs arranged as landward- and seaward-dipping large-scale cross bedding and/or plane bedding; these are probably storm breaker/surf deposits. The lower foreshore, though partially and sometimes totally bioturbated, shows landward-dipping small-scale cross bedding in very fine sands sorted by nearshore shoaling waves.
Tide- and storm-induced modification of the nearshore flow regimes therefore produces a distinctive shore-normal array of sedimentary facies. Each facies is characterised by diagnostic textural and structural signatures. A prograding sequence of such macrotidal deposits would be similar to, but more extensive than, a comparable microtidal sequence. 相似文献
3.
The Australian coast contains 10,685 beaches which occupy 49% of the 30,000 km coast and average 1.37 km in length. Their relatively short length is largely due to the presence of bedrock, calcarenite and laterite, which form boundaries to many of the beaches, as well as occurring as rocks, reefs and islands along and off the beaches. This geological inheritance plays a major role in Australian beach systems — determining their length and through wave refraction and attenuation influencing beach location, shape, type, morphodynamics and circulation, which in turn influence sediment transport and the backing dune and barrier systems. This paper uses a database covering every Australian beach to review the role of headlands, rocks and reefs on Australian beaches. Major effects are the short average beach length; reduction in breaker height resulting in lower energy beach types; wave refraction resulting in increased beach curvature; the presence of topographic rips on moderate and higher energy beaches and megarips during high wave conditions; and the interruption of and/or trapping of longshore sand transport leading to beach rotation. 相似文献
4.
Antonio H.F. Klein Óscar Ferreira Joao M.A. Dias Moyses G. Tessler Lucas F. Silveira Lindino Benedet Joao T. de Menezes Jose G.N. de Abreu 《Coastal Engineering》2010
This paper presents a comprehensive review on the interaction between hydrodynamic processes, beach morphology and sedimentology at large scale coastal behaviour along the coastline of Santa Catarina, between Laguna and São Francisco Island, a microtidal east coast swell environment with headland and bay geomorphologies. The parabolic bay shape equation has proven to be a convenient and practical tool for studying the stability of the headland-bay beaches, tombolos, and salients in Santa Catarina. The beaches exhibit different patterns of sediment removal as a function of the degree of beach curvature. In highly curved beaches, there is a well-developed shadow zone and a range of morphodynamic conditions, from a sheltered low-energy beach adjacent to the downdrift headland to a high-energy exposed beach on the straight end of the headland-bay beach. The less curved beaches instead, tend to show more uniform behaviour since they are directly exposed to incident waves. There is no obvious relationship between average wave height and mean grain size, showing the importance of sediment source to characterize the sedimentary distribution patterns in the study area. The analysis of beaches showed that beach morphodynamics and sequence profiles for a bay–headland coast in a microtidal east coast environment is a function of geological inheritance (e.g., distance between headlands and orientation, nearshore and inner shelf morphology, coastal plain morphology, and sediment source), and hydrodynamic factors (wave conditions, oceanic wave exposure and relative tidal range). 相似文献
5.
A.F. Velegrakis M.I. VousdoukasA.M. Vagenas Th. KarambasK. Dimou Th. Zarkadas 《Coastal Engineering》2007
This short contribution reports the results of a field study on the nearshore characteristics of waves generated by both conventional and high speed passenger ferries. The field observations took place in the late summer of 2005, at a beach close to the port of Mytilene (Island of Lesbos, Greece), and involved the visual observation of ship waves, using digital video recordings and image processing techniques. The results showed that passage of the fast ferry was associated with a longer, more complex and energetic nearshore event; this event not only did include higher nearshore waves (up to 0.74 m) and was organised in different wave packets, but it was also an order of magnitude longer (∼ 680 s) than the conventional ferry event. Regarding the effects on beach sediment dynamics, the fast ferry waves were estimated to be very efficient in mobilising the nearshore sediments in contrast to those of the conventional ferry. The fast ferry service appears to generate daily prolonged nearshore events, which contain waves with higher energy than those expected from the normal summer wind wave regime of the area; these events also include some high and very steep waves, which can be particularly erosive. Therefore, fast ferry wakes may have considerable impacts on the seasonal beach sediment dynamics/morphodynamics and the nearshore benthic ecology, as well as they may pose significant risks to bathers, affecting the recreational use of the beaches exposed to fast ferry traffic. Finally, the study has shown that satisfactory field observations of the nearshore characteristics of ship-generated (and wind) waves can be obtained using inshore deployments of calibrated poles, digital video cameras and appropriate image processing algorithms. 相似文献
6.
The infralittoral prograding wedge: a new large-scale progradational sedimentary body in shallow marine environments 总被引：1，自引：1，他引：0
F. J. Hernández-Molina L. M. Fernández-Salas F. Lobo L. Somoza V. Díaz-del-Río J. M. Alveirinho Dias 《Geo-Marine Letters》2000,20(2):109-117
A progradational sedimentary body, the infralittoral prograding wedge (IPW), has been developing from the mean fair-weather
wave-base level to the storm wave-base level between the onshore (beach) and the offshore (inner continental shelf) depositional
zones along the Spanish coast during the Late Holocene. The main sedimentary body is composed of large inclined master beds
which prograde seawards parallel to the shoreline, formed by sediments swept offshore by waves from shallow-water littoral
environments. The inclined beds downlap onto finer-grained offshore sediments and, in turn, are overlain by shoreface deposits.
The IPW is generated by downwelling storm currents and associated seaward transport of sediment. It represents a new depositional
model for clastic wave-dominated coasts, and its identification requires a new subdivision of the nearshore environment.
Received: 10 June 1999 / Revision accepted: 15 February 2000 相似文献
7.
珊瑚礁海岸在我国热带地区广泛发育,海滩-珊瑚礁海岸的动力地貌过程是认识该类海岸的关键。本文基于对海南铜鼓岭-高隆湾岸段的台风"威马逊"前后跟踪观测,讨论了海滩风暴响应特征及其与珊瑚礁发育之间的联系。结果表明该岸段海滩在"威马逊"风暴作用下响应最为剧烈的区带位于平均海平面(MSL)以上,表现为后滨冲越,以及岸线蚀退、滩肩变窄、滩面侵蚀等响应特征。海滩风暴响应特征与近岸珊瑚礁发育密切相关,在无珊瑚或珊瑚受损的岸段海滩响应剧烈,剖面平均变化率(MPC)为其他岸段的3~6倍,珊瑚礁通过消耗波能对相邻海滩提供良好保护。海滩-珊瑚礁系统对风暴的响应特征受控于珊瑚礁对海岸波浪的消耗能力和海滩固有的缓冲能力。基于本文研究结果,归纳出风暴极端动力条件下海滩-珊瑚礁海岸的4种风暴响应模式。 相似文献
8.
于2013年11月、2014年1月及3月在青岛市灵山湾海水浴场进行了3次表层沉积物采样,对粒度组分和粒度参数平面分布的变化进行了分析。结果表明,本区沉积物整体有变粗的趋势,细砂组分特别是极细砂和粉砂组分含量下降明显,分选性变好,正偏态及高峰度分布区扩大,粒度参数高值分布区被消除。粒径趋势分析表明,在涨潮流与强盛的冬季风驱动的风浪、沿岸流的综合作用下,研究区沉积物总体呈北东-南西向沿岸输运,运移趋势变化受到波浪、潮流水动力条件与地形相互作用的影响。短期的波能变化足以改变沙滩地貌,从而影响表层沉积物的分布。可为浴场维护提供理论依据。 相似文献
9.
Textural analysis is the epicenter of any sedimentological research. Granulometric analyses of unconsolidated sediments are used as an index to decipher the depositional environment. The granulometric analysis display a significant fluctuation in mean size, sorting, skewness, and kurtosis due to the variation in wave energy and the extent of turbulence affecting the beach environment during the crosshore and alongshore movement of sediments. The present study is to document the variation in grain size distribution within foreshore sediments, i.e., between the high water line and the plunge point wherein the sediments are deposited under different wave energy conditions. 相似文献
10.
Karl F. Nordstrom 《Marine Geology》1977,25(4):333-342
The purpose of this paper is to compare the differences between oceanside and bayside beaches. Field data on twelve beach process and response variables were gathered from February 1972 to April 1973 on four sample beaches at Sandy Hook Spit, New Jersey. Linear correlation is used to identify the most influential process variables and determine how the interrelationships among variables differ on each beach. The analysis confirms the importance of breaker height, wave steepness and wind direction on beach response. The correlation of beach processes with their associated responses are higher on the oceanside than on the bayside beaches, indicating that local, non-storm waves may be relatively insignificant in effecting substantial beach modification.Despite the greater magnitude of processes and beach change on the oceanside sites, erosion was more persistent on the bayside during the period of study. The frequent occurrence of short, steep erosional waves on the bayside prevented onshore movement of sediment between storms, resulting in a permanent loss of material from the beach face and dune. On the oceanside, long, low, depositional waves occurring between storms replenished most of the material carried away during the storm. This fresh beach material acted as a buffer against the erosion of the dunes during the following storm.The dominant bay waves are locally generated and may therefore be simulated using meteorological variables. However, the low wave energies on the bayside sites result in an increase in the relative importance of tidal currents, wind-induced currents, and refracted ocean swell. These factors complicate the application of simplified wave process—beach response models to the study of beaches exposed to these effects. 相似文献
11.
热带气旋前进方向两侧海滩风暴效应差异研究--以海滩对0307号台风"伊布都"的响应为例 总被引：11，自引：0，他引：11
在0307号台风“伊布都”(Imbudo)袭击华南沿海前后,对相距约300km的高栏岛飞沙湾(位于气旋前进方向右侧)和水东港下大海(位于气旋前进方向左侧)的固定海滩剖面地形及滩面沉积物进行了对比调查。调查结果表明,右侧海滩地形受台风暴浪冲击发生剧烈变化：后滨陆侧堆积,后滨向海侧及前滨滩面侵蚀(单宽侵蚀量达55m^3／m,平均海面(MSL)位置蚀退13m,岸线位置蚀退5m),以致剖面类型由滩肩式断面向沙坝式断面转变,表现出了海滩对台风做出快速响应;而左侧海滩剖面地形基本保持原状,虽也略呈侵蚀,但冲淤变化不大,表现为对台风做出迟缓响应。同时,从动力、滨海输沙、滩面沉积物变化和海岸地貌等方面对两侧海滩明显差异的风暴效应的机制进行了探讨。 相似文献
12.
13.
岬湾砂、砾质海岸是海岛、海岸带重要的旅游资源, 具有较高的社会经济和生态价值, 长期以来备受关注。本文以浙江朱家尖岛东岸的5个代表性岬湾海滩为例, 基于2019年台风季节早期、中期及晚期测量获得的海滩地形和沉积物数据, 结合海滩近岸的水动力数据, 分析了砂质海滩和砾石海滩这两种不同类型岬湾海滩的沉积地貌动态变化。结果表明, 朱家尖岛东岸5个海滩在台风季节出现了不同的体积变化, 大沙里、东沙、千沙、乌石塘和小乌石塘海滩的单宽体积变化分别为11.93m3·m-1、-54.41m3·m-1、-19.75m3·m-1、2.19m3·m-1和-1.96m3·m-1。砾石滩较砂质海滩更为稳定, 无人类活动干扰的砂质海滩在台风季节侵蚀更少、变化更小。台风季节大沙里、东沙、千沙、乌石塘和小乌石塘海滩表层沉积物的平均粒径分别为2.47Փ、2.24Փ、2.64Փ、-5.96Փ和-6.03Փ, 粒径粗化和离岸输运是5个海滩表层沉积物在台风季节的主要表现, 砂质海滩的沉积物粒度特征变化比砾石海滩要大。沉积物粒径、台风强度及台风期间的主要波向与海滩走向之间的关系、海岸工程这3种因素都可能对海滩在台风季节的沉积地貌动态变化产生影响。本文研究结果可为台风季节的海滩管理提供参考。 相似文献
14.
台风"艾利"对福建沙质海滩影响过程研究 总被引：6，自引：0，他引：6
通过对福建沙质海滩地形地貌现场调查,对比分析0418号台风“艾利”登陆福建前后各沙滩剖面的蚀淤变化,探讨了福建沙滩对台风“艾利”响应规律。研究结果表明,2004年8月底台风“艾利”过境期间,福建沿海砂质海岸显出了较强烈的地貌响应。沙滩剖面地形变化,冲淤相间,以冲蚀为主;后滨沙丘蚀退、滩肩蚀低、岸线向陆迁移是地貌响应的主要特征;沙滩沉积物的总收支趋于亏损。不同海岸类型的沙滩剖面对台风“艾利”的响应特征不同。岬湾型沙滩剖面地貌响应以前滨滩面侵蚀为主要特征。夷直型的长乐江田下沙剖面,对“艾利”台风的主要地貌响应特征为后滨沙丘、高潮带侵蚀,岸线后退超过16m,出现高度近1 m的直立侵蚀陡坎。沙坝-泻湖型沙滩剖面冲淤变化的主要特征是中潮带形成次一级沙坝。各沙滩的地貌风暴效应有自北往南依次减弱的趋势。 相似文献
15.
This work aims to contribute to the characterization and understanding of infragravity waves on two beaches with erosion problems. For this reason, we have used an array of ADCP and a pressure sensor to measure wave parameters and pressure inside and outside of the surf zone during the dry and rainy period in the beaches of Galerazamba and Manzanillo del Mar (both dissipative and eroded beaches) located in the Colombian Caribbean coast. Based on these measurements, we have carried out a spectral analysis in order to identify the frequency components that characterize the wave and its energy; thus, we identified the characteristic frequencies of infragravity waves to finally filter the infragravity signal on each beach in different seasonal periods. Among the results of the Welch spectrum applied to surface elevation time series, we found that, the frequencies'' energy of the sea-swell band decreases due to bottom friction and wave breaking as the wave approaches the shore, while the frequencies'' energy of the infragravity band increases significantly. In addition, for the wavelet analysis, we could observe how the energy of the infragravity band, especially the lowest frequencies gain energy as the waves approaches the coast. Furthermore, based on the infragravity wave obtained from the extreme wave event registered during the field campaign we can conclude that the contribution of this signal is important in the erosion problems presented in the beaches of Galerazamba and Manzanillo del Mar. Finally, these results show the need to realize other studies that allow us to understand deeply, the role of infragravity waves on the morphological changes that occurs in these beaches. 相似文献
16.
Hee Jun Lee Jong-Dae Do Sun Sin Kim Won-Kyung Park Kicheon Jun 《Ocean Science Journal》2016,51(4):681-694
Haeundae Beach represents Korean pocket beaches that are currently erosional and dominated by summertime typhoons. The decadal wave characteristics 9 km offshore of Haeundae Beach were analyzed using the WAM model that was validated through the 2007 wave observations. The wave statistics modelled for 1979–2007 indicates that the seasonal mean significant wave height (H s ) is highest (0.6–0.7 m) in summer due to typhoons, in contrast to the lowest (around 0.5 m) autumn analog. The wave direction is also pronouncedly seasonal with the principal bearings of SSW and NE in the summer and winter seasons, respectively. The WAM results additionally show that the H s has gradually increased over the region of Haeundae Beach since 1993. Beach profiling during June–November 2014 shows the opposite processes of the typhoon and fair-weather on beach sands. During a typhoon, foreshore sands were eroded and then accumulated as sand bars on the surf zone. In the subsequent fair-weather, the sand bars moved back to the beach resulting in the surf-zone erosion and foreshore accretion. A total of 5 cycles of these beach-wide sand movements yielded a net retreat (up to 20 m) of the shoreline associated with large foreshore erosion. However, the surf zone only slightly accumulated as a result of the sand cycles. This was attributed to the sand escape offshore from the westernmost tip of the beach. The present study may provide an important clue to understanding the erosional processes in Haeundae Beach. 相似文献
17.
In a novel finding for a beach environment, Poizot et al. (2013) identified an FB+ trend (sediments becoming finer, better sorted and more positively skewed upshore) on a well-developed swash bar on the upper foreshore of the Camposoto beach of Cádiz in SW Spain. In their Discussion of that paper, Muñoz-Perez et al. (2014) provide some supporting arguments and also report grain-size, beach profile and other data from nearby beaches which differ from those of Poizot and colleagues for Camposoto beach, pointing out that a trend observed on one beach may not apply to a neighbouring beach. However, even though the absolute values differ, the overall trends actually do show the same general behaviour. In our Reply to their comments, we also address some difficulties in comparing granulometric datasets generated by different analytical techniques. 相似文献
18.
A.D Short 《Marine Geology》1984,60(1-4):261-282
The morphology, texture and facies sequence on seven sand beaches, located in low, moderate and high wave energy, microtidal environments in southern Australia were investigated using box coring and Scuba observations. Systematic variation in facies occur both within and between the beaches. Low-energy reflective beaches are limited in lateral and vertical extent and in facies to beach laminations separated by coarse step deposits from finer nearshore cross-lamination facies. Moderate-energy intermediate beaches characterised by rip circulation possess increasingly wider surfzones with ridge and runnel and bar-trough facies separating the beach and step facies from the more extensive nearshore sequence. High-energy dissipative beaches may have 500 m wide surfzones containing multiple bar-trough topography. Fine beach laminations with backwash structures grade into 4–5 m thick bar-trough sequences then the extensive nearshore facies. As wave energy increases from low (Hb < 1 m) to high (Hb > 2.5 m) the vertical extent of the beach to nearshore sequence increases from <10 m to approximately 30 m, and the width from 100 m to several kilometres. Consequently one would expect higher-energy paleo-beach sequences to be represented more by diagonal than vertical facies sequences. 相似文献
19.
Dissipative and reflective beaches in a large lake and the physical effects of lake level regulation
Mark S. Lorang Jack A. Stanford F.Richard Hauer Jon H. Jourdonnais 《Ocean & Coastal Management》1993,19(3)
Nearshore environments in Flathead Lake, Montana, USA, were described as dissipative or reflective on the basis of: the surf similarity parameter , grain size, morphology, number of breaking waves and angle of wave incidence. The relative resistance to foreshore and backshore erosion caused by anthropogenic lake level regulation was compared between these two nearshore configurations. Reflective systems were characterized by dynamic gravel beach faces and steep inshore shelves armored by wave-washed cobble. In contrast, dissipative systems were characterized by sand-sized substratum, broad flat inshore shelves and the presence of multiple linear bars approximately 350 m offshore. Five decades of regulated lake levels have resulted in extensive shoreline erosion (970 ha on the north shore of the lake) and a general reshaping of both types of nearshore environments, although dissipative shorelines eroded faster (5.7 m/year maximum and 2.0 m/year average). The presence of docks and other man-made structures on reflective beaches accelerated erosion by intercepting longshore gravel transport. This analysis provided a physical basis for understanding the effects of lake level regulation on shoreline ecology and management. 相似文献
20.
Abraham Golik 《Estuarine, Coastal and Shelf Science》1982,15(3):267-276
A fortnightly sampling of tar balls on six beaches along the Israeli coastline between 14 April 1975 and 25 June 1976 showed that the mean content of tar during that period was 3625 g m?1 of beach front. The northern and central parts of the coast were significantly more polluted than the southern part. Between July 1975 and February 1976 the mean tar quantity decreased continuously from 5635 to 1344 g m?1.A comparison of tar quantities on the Israeli beaches with those of other beaches in the world showed that the Israeli beaches are more polluted than those of the west Atlantic coast, are as polluted as other beaches on the eastern coast of the Mediterranean Sea, and are less polluted than the beaches of Alexandria, Egypt, and Paphos, Cyprus. It is suggested that the tar content on the beach is related to the degree of oil pollution in the sea. The closer a beach is to an oil shipping lane or an oil dumping site, the heavier it is polluted.During storms, beach tar balls are pushed by the waves to the back of the beach or, in the case of a cliffed coast, are carried along the shore by the longshore current. When the tar balls reach a gap in the cliff (such as an estuary), they are carried inland by the storm waves. There the tar may become buried or dry, shrink and break into small particles which are then dispersed by the wind. 相似文献