海滩风暴效应若干问题思考与我国研究前景

热带风暴是一种频发的灾害性事件,其诱发的大浪及其伴生的风暴潮会在短时间内搬运大量沉积物,对海岸地貌、海底地形和海洋沉积的影响极为严重.总结了未来风暴变化趋势和风暴动力方面的研究进展,概述了近几十年来海滩风暴效应领域几个重要方向的进展,内容包括岸滩风暴灾害调查和研究、海滩风暴效应差异性研究、风暴作用下的泥沙运动和岸滩风暴响应沉积学特征等方面.从国内外的研究现状来看,我国在风暴作用下泥沙运动实测与定量分析、多因素耦合控制下海滩风暴效应差异和海滩风暴地貌过程等方面存在着明显的不足.作为我国海岸科学研究中必需又薄弱的环节,今后该领域的研究应该在强化野外现场实验和监测的基础上,深入探讨极端条件下的海滩过程,发展海滩风暴响应预测模型,并积极开展海滩风暴潮防护技术开发与应用.     

琼州海峡南岸海岸动力地貌研究

岬湾相间的琼州海峡南岸在海岸动力条件作用下,岸滩发生侵蚀或堆积,特别是南岸中部的南渡江三角洲沿岸岸滩演变剧烈。该文从海岸动力地貌的角度,对琼州海峡南岸的海岸动力特征、泥沙运动以及岸滩演变进行分析。根据海峡南部三维潮流场数值模拟结果,结合经验公式初步分析潮流引起的泥沙运移速率和方向,得到岸外水域总的泥沙运移趋势为从西向东。根据波浪动力计算分析沿岸泥沙运移,探讨沙质岸滩的动态与地貌演变之间的关系,得出海峡南岸海岸地貌演变与盛行的NE和NNE向风浪有密切关系,岸滩的演变过程主要受制于这两个方向的风浪及其引起的泥沙沿岸运移。     

围海工程对邻近港区泥沙回淤的影响研究—以漳州港招商局中银码头区为例

针对港区附近围海造地造成的港区泥沙回淤量增大问题，以漳州港招商局中银码头区为例，全面分析了漳州港海域的地形地貌、水动力特征、泥沙特性和岸滩自然演变。根据工程建设前后地形变化，结合岸线回填量和九龙江输沙资料，分析了围海造地对岸滩演变及港区码头回淤的影响。研究表明，围海工程实施后，邻近港区的泥沙回淤由自然回淤、滩地抬高和回填引起的浑水回淤三部分组成。当围海工程结束，新岸滩调整达平衡后，泊位及港池的回淤将逐渐降至正常自然回淤强度。     

广西万尾岛金滩沿岸输沙计算与分析

依据CERC公式,年内代表浪向作用下,广西万尾岛金滩平直岸滩中部泥沙分别向东西两侧净输沙,意味着金滩中部有淘刷趋势而两端有淤积趋势,而实际上岸滩中部滩面长年基本稳定、未有明显侵蚀现象。分析认为公式计算成果反映的输沙特征定性仍然是正确的,岸滩能够维持稳定是因为还存在自海向岸的横向输沙补给沙源。当岸滩并非平直且足够长时,应完整分析纵、横向输沙才能更为合理地反映岸滩泥沙运动特征。     

Investigation of the effects of offshore breakwater parameters on sediment accumulation

Littoral sediment transport is the main reason for coastal erosion and accretion. Therefore, various types of structures are used in shore protection and littoral sediment trapping studies. Offshore breakwaters are one of these structures. Construction of offshore breakwaters is one of the main countermeasures against beach erosion. In this paper, offshore protection process is studied on the effect of offshore breakwater parameters (length, distance and gap), wave parameters (height, period and angle) and on sediment accumulation ratio, one researched in a physical model. In addition to the experimental studies, numerical model in which the formulae of the sediment discharge (i.e. the formulae of CERC and Kamphuis), was used was developed and employed. The results of the experimental and numerical studies were compared with each other.     

近岸波、流作用下结构物附近海岸演变的数值模拟

针对与砂质海岸在波浪作用下的演变有关的波浪、近岸流及输沙问题进行了系统的研究,并对结构物附近海岸演变进行了数值模拟。考虑了波浪折射-绕射及波浪破碎的综合作用,在近岸流场的模拟中用沿水深积分形成的K方程模型确定涡粘系数。计算岸滩地形变化时,综合波浪、近岸流作用的底沙和悬沙输沙率,并考虑波浪对泥沙作用的影响。模型对防波堤和近岸沉船附近地形变化进行了模拟,效果良好。     

An investigation on the formation of submerged bar under surges in sandy coastal region

Cross-shore sediment transport rate exposed to waves is very important for coastal morphology,the design of marine structures such as seawalls,jetties,breakwaters etc,and the prevention of coastal erosion and accretion due to on-off shore sediment transportation.In the present study,the experiments on cross-shore sediment transport are carried out in a laboratory wave channel with initial beach slopes of 1/8,1/10 and 1/15.By using the regular waves with different deep-water wave steepnesses generated by a pedal-type wave generator,the geometrical characteristics of beach profiles under storm conditions and the parameters affecting on-off shore sediment transport are investigated for the beach materials with medium diameters of d50=0.25,0.32,0.45,0.62 and 0.80 mm.The offshore bar geometric characteristics are the horizontal distances from the shoreline to the bar beginning(Xb),crest(Xt),and ending(Xs) points,the depth from the bar crest to the still water level(ht),and the bar volume(Vbar).The experimental results have indicated that when the deep-water steepness(H0/L0) increased,the net movement to seaside increased.With the increasing wave steepness,the bars moved to widen herewith the vertical distances from still water level to the bar beginning(Xb),crest(Xt) and ending(Xs) points and the horizontal distances from the coast line to the bar beginning,crest and ending points increased.It was also shown from experimental results that the horizontal distances from the bar beginning and ending points to the coast line increased with the decrease of the beach slope.The experimental results obtained from this study are compared with previous experimental work and found to be of the same magnitude as the experimental measurements and followed the expected basic trend.     

Numerical modelling of sand beach evolution around coastal structures

I~crIOWIn the coastal area, especially at the sandy seashore, wave and nearshore current are the major factors which affect sediment transPOrt and the motyhChdynamics.The numerical models of predicting the beach evolution can be classified intO the medi~term and long-term models according to their space and time scales (De Briend et al., 1993;Watanabe, 1990; Watanabe et al., 1986; Tao, 1996). In the medium-term model the effects ofwave, nearshore current and sediment transport are conside…     

滩海油田泥沙运移控制初步方案及试验研究

为了降低成本,维持滩海油田的开敞式开发,提出了滩海油田泥沙运移控制初步方案,并进行了物模试验验证。该方案充分利用自然力,通过人工干预促使防护区外泥沙起动,借助海上潮流使高含沙海水流经防护区,实现岸滩蚀退的快速防护,对滩海油田的防护具有指导意义。     

南渡江三角洲海岸泥沙纵向运移与岸滩演变的响应

南渡三角洲沿岸在盛行ＮＮＥ向波浪等动力条件的作用下,泥沙产生纵向运移,岸滩遭受侵蚀或堆积,岸滩演变剧烈。本文利用基于网格的波注折射绕射模型,分析南渡江三角洲海岸波浪动力过程、破波带波能与辐射应力分布及其引起的沿岸泥沙纵向运称。浴海岸动力学地貌的角度,通过三角洲沿岸波浪动力特征、泥沙运动的分析,探讨沙质岸滩的动态与地貌演变。     

人工岬角和海滩养护下泥沙输运与海床演变

实施人工岬角和海滩养护的软硬措施相结合的方法是探索解决海滩侵蚀问题的新举措之一。基于验证良好的水动力模型建立了泥沙输运和海床演变模型,对秦皇岛市新开河口至南山岸线海滩经整治修复工程实施后的泥沙输运和海床演变规律进行模拟分析。结果表明:大潮与常浪耦合作用下,研究区域周围海域流速整体上落急时刻大于涨急时刻,沙坝掩护水域的流速较弱,波浪在沙坝处增强并在沙坝后破碎并减弱;在沙坝处出现高悬沙浓度区域,悬沙浓度分布主要由底床切应力控制,部分受水动力影响。大潮与强浪耦合作用下,在沙坝处出现远大于常浪时的增强水流(波生流),方向与强浪向一致,波浪在沙坝处已破碎且沙坝对强浪的削减效率大于常浪;与常浪作用下不同,悬沙浓度场在强浪作用下沙坝处没有出现明显的高浓度区域。波流耦合作用下,人工岬角单独存在时护岸效果有限,工程实施后在人工岬角和人工沙坝的配合下,沙坝处侵蚀而沙坝后侧掩护区域淤积,沙坝起到了有效养护海滩的作用。     

海南岛新海湾海滩地貌状态与海岸泥沙纵向运动特征

根据１９９０年现场调查及前期观察资料，论述了海南岛新海弧形海湾不同岸段由主要动力驱动过程和海滩地貌结构组成的４种海滩地貌状态，为Ⅰ．隐蔽段消散类型，Ⅱ．脊－沟体系与低潮台地类型，Ⅲ．韵律海滩与砂坝类型，Ⅳ．开敞段消散类型。应用泥沙粒级参数概率模型分析近岸泥沙纵向运动趋势，结果表明，常波况下，沿岸泥沙存在双向运动，湾顶海滩为汇集地带，泥沙纵向运动主趋势为西南向；高能条件下，海岸北段可出现北向泥沙运动     

季节性波浪动力作用下南湾弧形岸滩泥沙横向输运特征

响应季节性波候作用的泥沙输运特征是研究弧形海滩地貌变化及港工建筑的重要内容。基于南湾弧形海滩实际测量的冬、夏各11条剖面高程变化资料,将其划分为低潮间带、低中潮带、中潮带、高潮间带、低冲流带、中冲流带及其海滩后滨等7带,在此基础上利用经验正交函数(EOF)方法对各个带的体积变化进行分析,结果表明:1)南湾弧形海滩的泥沙以单向输运为主,并具有季节性变化特征,其中冬季泥沙在东南浪作用下,自陆向海输运,夏季泥沙在西南浪作用下自海向陆输运;2)南湾弧形海滩的泥沙分别在高潮带与中潮带、低冲流带与中冲流带之间存在频繁的双向输运;3)南湾弧形海滩不同岸段泥沙的横向输运因岬角的遮蔽能力、地形以及波浪作用的方向而有所差异。     

海岸破波带内悬沙空间分布试验研究和解析表达式

关于海岸破波带内悬沙浓度水平和垂向分布的研究对于计算海岸输沙率和地形演变具有重要意义。本研究进行了规则波、波群和不规则波三种波浪情况破波带内悬沙浓度的水平和垂向分布的试验测量。试验在大尺度波浪水槽进行,接近实际海岸波况尺度。给出了破波带内多断面悬沙垂向分布的细致测量结果,并以此为基础给出了预报实际海岸破波带内悬沙浓度水平和垂向分布解析表达式,讨论了形成这些分布的物理原因和不同波况、不同破波带区域对分布的影响。     

Managing erosion-induced problems in NW Mediterranean urban beaches

The applicability of recommendations of the Eurosion project to define a policy to manage coastal erosion has been tested at the “beach” scale in the Mediterranean coast. Thus, a favourable sediment status has been defined for these beaches taking into account their main functions: recreation and protection. Because they act at two different seasons, this status needs to be seasonally defined. For the protection function, the favourable sediment status depends on the level of safety fixed by the manager taking into account the importance of existing infrastructures and, for recreation it depends on the use density of the beach. The concept has been formalized for beach management within a framework where benchmarking plays a crucial role to determine the need of intervention. This has been illustrated for open cell beaches where one of its boundaries can permit variations in the sediment budget and for pocket beaches that act as closed sediment cells.     

岬湾海滩岬角沙丘过路输沙研究现状

文章从岬湾海滩、岬角沙丘以及岬角沙丘过路输沙的概念出发,引出岬角沙丘过路输沙的概念模式,总结岬角沙丘过路输沙的常用研究方法和研究现状,指出岬角-海滩-沙丘系统在海岸带输沙中的重要作用;针对我国海岸风沙地貌研究的现状,提出应加快海岸风沙资源现状调查、加强海岸风沙地貌过程研究以及协调海岸风沙地貌资源开发利用与修复保护,为我国海岸沙丘相关研究明确方向。     

Modeling sediment transport in the swash zone: A review

A critical review of conceptual and mathematical models developed in recent decades on sediment transport in the swash zone is presented. Numerous studies of the hydrodynamics and sediment transport in the swash zone in recent years have pointed out the importance of swash processes in terms of science advancement and practical applications. Evidently, the hydrodynamics of the swash zone are complex and not fully understood. Key hydrodynamic processes include both high-frequency bores and low-frequency infragravity motions, and are affected by wave breaking and turbulence, shear stresses and bottom friction. The prediction of sediment transport that results from these complex and interacting processes is a challenging task. Besides, sediment transport in this oscillatory environment is affected by high-order processes such as the beach groundwater flow. Most relationships between sediment transport and flow characteristics are empirical, based on laboratory experiments and/or field measurements. Analytical solutions incorporating key factors such as sediment characteristics and concentration, waves and coastal aquifer interactions are unavailable. Therefore, numerical models for wave and sediment transport are widely used by coastal engineers. This review covers mechanisms of sediment transport, important forcing factors, governing equations of wave-induced flow, groundwater interactions, empirical and numerical relations of cross-shore and longshore sediment transport in the swash zone. Major advantages and shortcomings of various numerical models and approaches are highlighted and reviewed. These will provide coastal modelers an impetus for further detailed investigations of fluid and sediment transport in the swash zone.     

粤东南澳岛青澳海滩侵蚀退化风险评价及其安全调控

分析了南澳岛海滩资源储量、空间分布及其开发利用现状,开展海岛海滩侵蚀风险评价,选择青澳海滩开展岸滩及其海湾海床地形、沉积物、动力泥沙调查,分析探讨了青澳海滩泥沙动力沉积特征,灾变退化过程机制,并从海滩稳定性和游客安全角度给出安全调控建议。结果表明:1)南澳岛海滩资源储量与侵蚀风险区域分异特征明显,其中青澳海滩旅游活动频繁、开发强度大,侵蚀退化风险等级高,人为破坏干扰抑制滩海泥沙交换,无序无度占滩开发与利用破坏了海滩自然演化进程,短期过量旅游活动加速海滩侵蚀退化进程;2)青澳湾沉积物以粗粒砂为主,沙源供给不足,不同岸段岸线进退与岸滩蚀淤与海滩方位、波浪动力强度强弱关系密切,具有明显的纵向沉积地貌分带特征。湾内落潮优势流(SE)优于涨潮(NW),对泥沙输运进入湾内具有抑制作用,潮周期海湾泥沙自湾内向湾外输运,泥沙以外输为主单宽输沙为3 400 t;3)青澳海滩存在严重的"无序占滩建筑,污水肆意排放,管理不规范"等问题,监测评价亦表明侵蚀退化风险巨大,游客安全面临着风险隐患,建议青澳海滩实行以生态化养护开发和"游客为中心"为理念的安全调控措施,设立红线及安全标示。该研究为岛礁生态建设、海岛保护及修复提供科学依据。     

Multigrain sedimentation/erosion model based on cross-shore equilibrium sediment distribution: Application to nourishment design

In the light of global warming and sea level rise there are many coastal beaches that suffer from erosion. Beach nourishment has become a common practice to maintain the sediment balance on a shore-face. In this paper, a three-dimensional numerical model for evaluating long-term impact of beach nourishment projects has been developed. The model addresses the longstanding complex issue of coastal morphology and sediment grain size distribution from an unconventional angle, which exploits the strong links between grain size distribution and the prevailing transport direction of each sediment constituent under ‘average’ wave and storm action. The present model predicts the redistribution of nourished sediment according to the subtle clues implied by equilibrium distribution curves and latest coastal wave transformation theories. After verification against recent field observations in Terschelling, The Netherlands, the model was used to predict long-term effects of different beach nourishment strategies. It was found that: (a) given the source sediment available in Terschelling the tactics of large volume and less frequent implementation are better than otherwise; and (b) from a pure engineering point of view, waterline nourishment outperforms offshore trough nourishment.The model offers an additional tool for coastal engineers to evaluate the feasibility, effectiveness and the optimization of dumping locations for beach nourishment projects. It is also a useful tool for stratigraphic modelling of shallow-marine sedimentation in conjunction with sea level changes.     

岬间海滩泥沙输运趋势与剖面分形研究

根据1999年7月实测的粤东岬间海滩沉积与地形变化资料,采用沉积物输运概率模式(McLaren模型)对海滩沿岸泥沙运移趋势进行探讨。结果表明,在常波况条件下海滩沿岸泥沙向偏南方向运移,在高能条件下可能出现与常波况条件下相反运动的趋势。进一步利用分形分布模型研究了海滩剖面的分形性质,提出了岬间海滩剖面地形变化的短期分形预测模型。