The formation of offshore ripples in the zone under irregular waves

In this article, results obtained from an experimental investigation conducted to determine the wave-induced geometric characteristics of offshore ripples and bars are presented. The experiments were performed using irregular waves. Natural beach sand was used in the study, where the mean diameter was 0.35 mm and the specific gravity was 2.63. The initial slope of the beach was 1:5. Different wave groups were generated over the initially flat beach, and a number of characteristics were determined. These include the ripple number, individual and average ripple heights, individual and average ripple lengths and the length of the offshore bar. The results of the experimental study were evaluated and empirical expressions based on the results were formulated.     

厦门海滨浴场的环境质量及容量研究

本文依据现场调查及测验结果，综合分析、评估厦门市海滨浴场的资源与质量的现状及存在问题，并依据现有沙滩资源估算海滨浴场的客容量。结合厦门作为国际港口风景旅游城市的发展趋势，提出采用人工造滩的方法来增添新的海滨浴场，不仅可以改善海滨浴场的布局，同时还可以增加客容量。     

Variation in Surf-zone Fish Community Structure Across a Wave-exposure Gradient

Fluctuations in various attributes of a surf-zone fish community were examined by beach seining at a series of sites spanning a wave-exposure gradient in the Saldanha Bay–Langebaan Lagoon system, on the South African west coast. During April 1994, 24 species, totalling 25 676 individuals and 434 kg, were captured. Three teleosts,Atherina breviceps, Liza richardsoniiandPsammogobius knysnaensis, dominated numerically, while three elasmobranchs,Rhinobatos annulatus, Mustelus mustelusandMyliobatis aquila, dominated the biomass. Elasmobranchs displayed no discernible distribution patterns. Two important trends were, however, evident in the teleost catches: overall teleost abundance (mean density) increased markedly as wave exposure decreased; and highest species richness and diversity, and lowest dominance were both recorded at intermediate levels of exposure. A positive relationship between fish size and exposure was also evident for at least two of the species. These trends were attributed primarily to the availability and abundance of suitable food resources, and to physical disturbance introduced by breaking waves.     

华南沿海海滩状态和演变

根据华南沿海不同区域和不同形态海滩的地形和碎波参数计算分析，得出本区存在着４种平均海滩状态：（１）消散优势型海滩；（２）沿岸坝－槽型海滩；（３）沿岸坝沟或低潮阶地型海滩；（４）反射优势型海滩。华南海滩状态除有长期的侵蚀趋势外，存在明显的季节演变，它与波浪作用的变化关系密切；此外，人为建造的海岸工程也可引起海滩状态的变化，今后在其开发利用中必须予以注意。     

人类工程活动对秦皇岛海滩侵蚀及淤积的影响

秦皇岛地区旅游性海滩的侵蚀主要是人类所实施的以水库为主的河流水利工程而产生的海岸效应。在区域性海滩普遍遭受侵蚀状态下，沿海港口工程又通过三种不同形式第滩发育施以影响，其一是对沿岸泥沙流的拦阻，其二为在局部岸段形成完全或不完全波影区，其三为人工岬湾的形成，港工引成的海滩淤积体特征是海滩变宽、变缓及海滩砂细化。文中最后讨论了侵蚀性海滩向演化的发育空间问题。     

Forcing of large-scale cycles of coastal change at the entrance to Willapa Bay, Washington

Anomalous morphological features within large estuaries may be: (1) recorders of external forces that periodically overwhelm the normal morphodynamic responses to estuarine energy fluxes, and (2) possible predictors of cycles of future coastal change. At the entrance to Willapa Bay, Washington, chronic beach erosion and frequent coastal flooding are related to the historical northward channel migration that destroyed the protective sand spits of Cape Shoalwater. Northward channel migration since the late 1800s conforms to the long-term net sediment transport direction. What requires explanation is periodic southward relocation of the trunk channel by as much as 5 km, and attendant construction of moderately large sand spits on the north side of the bay such as Kindred Island, Tokeland Peninsula, and Cape Shoalwater.Both autocyclic and allocyclic processes may have been responsible for trunk channel realignment and associated spit deposition. Channel recycling may occur when the main channel becomes overextended to the north and the tidal flow is inefficient because of its decreased gradient and increased susceptibility to shoaling by the growth and migration of tidal sand ridges. Under those conditions trunk channel relocation would be facilitated by increased wave heights and water levels of El Niño winter storms. However, co-seismic subsidence is the most likely mechanism for abruptly increasing sand supply and longshore transport that would favor discrete periods of channel relocation and spit deposition. Unless external forcing changes sand supply and predominant sediment transport directions in the future, the relative rise in sea level, frequent winter storms, and local deficit in the sand budget assure that beach erosion will continue at the mouth of this large estuary.     

山东半岛若干平直砂岸近期强烈蚀退及其后果

近几十年来,大洋海面的可能上升,引起了世界性的砂岸蚀退。山东半岛的砂岸,不仅受这世界性因素的影响,而且因河流入海泥沙被水库拦截,工农业超采地下水,径流濒于枯竭,以及人工过量采砂,造成海滩砂亏损约2000万吨/年。半岛平直砂岸的蚀退率达2米/年左右,远高于世界上同类砂岸的蚀退率。因此,冲毁了某些海滩防风林,威胁着良田和建筑物的安全,咸化了地下水。未来将日益严重,必需引起有关方面的严重关注,迅速采取措施,合理开发海滩,筑堤防岸,建立建全海岸保护法。     

西沙群岛现代滨岸的风暴沉积

本文仅以1984年10号风暴为例,讨论了风暴前后的水动力条件及路径变化.重点阐述了该次风暴对西沙珊瑚礁区的潮间和潮上带现代砾堤和海滩的影响.描述了珊瑚礁区的砾堤沉积物的空间分布及垂向序列,并对沙质海滩的风暴搬运过程进行了适当的讨论.西沙砾质砾堤和沙质海滩无论从沉积序列上还是从沉积物的结构成份上,都存在着较大的差异,它们是在一种水动力条件下形成的两种不同的沉积体,在沉积过程中各有自身的沉积特点.本文尝试性地从上述角度提出一种沉积序列的空间格局,以便为古代沉积物的研究提供一些滨岸风暴沉积的信息.     

海洋底栖甲藻的浮游行为特征研究

研究了日本濑户内海屋岛湾沙质海滩底栖甲藻中具有底栖－浮游兼性行为的种类及其浮游行为特征。发现具有游游兼性特征的有8种，分别是Amphidinium carterae,A.klebsii,A.herdmanae,Gymnodinium sp1,G.pyrenoidosum,Peridinium quinquecorne,Prorocentrum emarginatum和Pror.sp1,几乎全是该潮间带底栖甲藻的优势种，占水样中甲藻种数的11．6％，个体数占海水样品中甲藻总个体密度的0－51．3％，具有明显的季节性，当这些种类在沉积物样品中数量较少时，在海水样品中就极少出现，具有随潮汐变化的行为特征。研究表明这些种类是真底栖种，浮游生活只是其兼性行为特征，是长期进化和对潮间带特殊环境适应的结果，本文还探讨了底栖甲藻的浮游习性及其与内湾近岩赤潮的关系和可能产生的影响。     

Deducing sediment transport direction and the relative importance of rivers on a tropical microtidal beach using the "McLaren model"

 Analyses of the sedimentological trend from 90 samples collected at 1-km intervals along a tropical microtidal coastline of northern Terengganu indicate that the preferred sediment transport direction was northwards, following the McLaren model. The extent of disruption to and reestablishment of the sedimentological trend on beaches north of two river mouths within the study area was used to determine their relative importance in supplying sediment to the beaches. The extent of disruption to the sedimentological trend was 18 and 14 km for the beaches north of the Terengganu and Setiu River mouths, respectively. This suggests that the Terengganu River is more important in supplying sediments to the beach than the Setiu River. To a limited extent this study showed that the McLaren model can be applied to deduce sediment transport direction on a microtidal coastline, while disruption to the sedimentological trend adjacent to river mouths can be used to compare the relative importance of rivers in supplying sediments, provided that the disruption to the sedimentological trend is small enough so as to allow for the trend to be discernible again further along the transport path. Received: 8 May 1997 · Accepted: 12 August 1997