Review of Countermeasures against Beach Erosion on the Taiwanese Coast

Beach erosion is one of the most significant coastal preservation problems in the world. This study first briefly addresses the influences of human activity on beach erosion. The seriousness of beach erosion in Taiwan has received considerable attention since the 1960s, following rapid population growth and economic development in the coastal areas. Hard solutions of stabilized structures against beach erosion in Taiwan at that time are reviewed based on their effectiveness in protecting property and their ability to produce a landscape that harmonizes with the adjacent coastal environment. Soft coastal defense solutions implemented recently in coastal regions in Taiwan are introduced and their benefits are discussed. This study concludes that various methods designed to prevent wave- and current-induced beach erosion should be based on analyses of nearshore hydrodynamics, sediment transport, coastal processes, and physiographic features of beaches.     

人工沙滩在堤后次生波作用下的稳定性试验

基于波浪泥沙物理模型,考虑不同水位条件、不同重现期的波浪作用以及复坡和单坡2种不同坡度的沙滩坡面,对斯里兰卡科伦坡港口人工沙滩的冲淤情况及稳定性进行试验研究。结果表明,在次生波作用下,沙滩出现了不同程度的冲刷,沙滩剖面出现冲刷的主要部位一般位于水面线以下的波浪破碎带内,但当波浪条件增大时,人工沙滩剖面在水面线以上也呈普遍冲刷状态。在试验工况范围内,外海水位越高,波高、周期越大,防波堤堤后的次生波越大,所造成的沙滩剖面变形越大,冲刷深度越大。复坡和单坡2种不同坡度方案滩面泥沙在次生波作用下的冲淤部位基本相似,剖面稳定性相当。     

几种典型海滩平衡剖面模型中参数意义的探讨

海滩平衡剖面是海岸近岸过程研究的一个重要概念,在海岸工程中有应用价值。通过分析认为粤东后江湾的海滩剖面处于动态平衡状态。应用Dean、Bodge和Lee等3种海滩平衡剖面模型对后江湾的海滩剖面数据进行拟合,并从地形动力学的角度对拟合结果进行了分析解释,结果表明3个模型中的参数分别包含有波浪周期或波长、剖面变化渐近深度、海滩反射性等物理意义。这可为海岸工程设计确定近岸水下地形轮廓提供重要的依据。     

Wakes from Large High-Speed Ferries in Confined Coastal Waters: Management Approaches with Examples from New Zealand and Denmark

Large high-speed craft carrying passengers and vehicles produce wake waves that are different from both conventional vessels and smaller fast vessels. Wakes from these high-speed craft can cause environmental problems (such as beach change, ecological disturbance, and damage to structures and archaeological sites) and safety problems (for navigation and for users of the beach and nearshore) in confined waters. As a consequence of the higher speed, the vessel wakes also have a longer period than wakes caused by conventional ships and may lead to substantial wave action in shallow water environments. In both New Zealand and Denmark, issues relating to high-speed craft wakes were not addressed until after the vessels had begun operation, and complex coastal management issues with possibly broader application have had to be addressed. Emerging management strategies have involved regulation using speed and wave height criteria.     

Y形整治建筑物护滩效果分析

近年来,在航道整治工程中采用了一种外形类似"Y"的整治建筑物,取得了较好的护滩效果。选取长江下游典型潮汐分汊河段——白茆沙河段进行地形概化,采用潮流数学模型研究Y形建筑物的护滩效果。结果表明,护滩堤一般就近布置在需守护的滩体前沿等深线附近,护滩堤长度需覆盖滩体迎流面最宽处,护滩堤高程可取潮汐分汊河段特征水位;头部潜堤一般沿滩脊线布置,长度延伸至需守护的低滩,可根据多年历史地形资料选择在滩体稳定的等深线附近,高程则以可满足整治建筑物结构安全即可。     

A Review of Beach Bye-Law Usage in Supporting Coastal Management in Ireland

Coastal areas are commonly the focus of a range of human activities and uses. Beaches are one example of multi-use coastal environments, accommodating activities linked to leisure and recreation, amenity, conservation and business, often simultaneously. Ireland is no different in this regard, as its beach resources provide a range of goods and services of societal value. Ireland has 16 coastal counties and their associated local authorities have a beach management remit, a role that can present a number of challenges. The use of beach bye-laws is one option to support management of beach environments by local authorities. Local authority personnel tasked with beach management from each coastal local authority were surveyed to assess the actual and potential role of beach bye-laws in contributing to more effective management of beach environments and to broader coastal management. Usage of beach bye-laws varied across local authority areas and evidence suggested that the efficacy, use, and implementation of beach bye-laws differed from county to county. Beach bye-laws offer potential but interaction with other initiatives as part of a wider program for coastal management may yield improved results.     

杭州湾北岸水下地形冲淤演变分析

通过分析历史资料,研究了杭州湾北岸上海市化学工业区堤防前沿的水动力特征、岸滩的冲淤演变特征及部分可能影响因素.针对化工区海防安全的要求,着重分析了堤防工程的若干工程效应及其对该水域岸滩保护的工程作用.针对该水域的最大海洋自然灾害-台风浪,汇总了工程建设前后几次强台风过境该水域时的若干水动力条件及岸滩损坏情况,分析了若干...     

Preoperational ocean forecasting in the southeastern Mediterranean Sea: Implementation and evaluation of the models and selection of the atmospheric forcing

Within the framework of several local and international programs, a quasi-operational ocean-forecasting system for the Southeastern Mediterranean Sea has been established and evaluated through a series of preoperational tests. The Princeton Ocean Model (POM) is used for simulating and predicting the hydrodynamics while the Wave Model (WAM) is used for predicting surface waves. Both models were set up to allow varying resolution and multiple nesting. In addition, POM was set up to be easily relocatable to allow rapid deployment of the model for any region of interest within the Mediterranean Sea. A common requirement for both models is the need for atmospheric forcing. Both models require time varying wind or wind stress. In addition, the hydrodynamic model requires initial conditions as well as time dependent surface heat fluxes, fresh water flux, and lateral boundary conditions at the open boundaries. Several sources of atmospheric forcing have been assessed based on their availability and their impact on the quality of the ocean models' forecasts. The various sources include operational forecast centers, other research centers, as well as running an in-house regional atmospheric model. For surface waves, higher spatial and temporal resolution of the winds plays a central role in improving the forecasts in terms of significant wave height and the timing of various high wave events. For the hydrodynamics, using the predicted wind stress and heat fluxes directly from an atmospheric model can potentially produce short range ocean forecasts that are nearly as good as hindcasts forced with gridded atmospheric analyses. Finally, a high-resolution, nested version of the model has shown to be stable under a variety of forcing conditions and time scales, thus indicating the robustness of the selected nesting strategy. For the southeastern corner of the Mediterranean, at forecast lead times of up to 4 days the high-resolution model shows improved skill over the coarser resolution driving model when compared to satellite derived sea surface temperatures. Most of the error appears to be due to the analysis error inherent in the initial conditions.     

Development of Green-Naghdi models with a wave-absorbing beach for nonlinear, irregular wave propagation

Two-dimensional and three-dimensional Green-Naghdi (GN) models equipped with a numerical wave-absorbing beach have been developed to simulate nonlinear, regular, and irregular wave propagation. The numerical beach is introduced near the downstream boundary to absorb outgoing waves. An appropriate amount of numerical damping and an appropriate length of numerical beach are investigated using numerical experiments. The results show that the GN models with a numerical beach work very well in simulating wave propagation in water in a small computational domain.     

Indicators for Evaluating the Impact of Artificial Islands on the Barcelona Coast

Artificial islands have been constructed next to large cities due to the need for extra space in highly populated areas. These emerged structures have been used by many countries as platforms for developing infrastructure (airports, harbors, highways, etc.), rebuilding ecological areas, and creating new spaces for tourism or residential areas. In this study, two state-of-the-art numerical models for wave propagation and nearshore circulation are used to simulate the effects of an emerged artificial island on the Barcelona coast. Several sea indicators (wave height, intensity and direction of currents, and mean water level) are analyzed to assess the changes likely to be induced by an artificial island. Three different situations are studied and the indicators are compared across the different tests to obtain information that can be used in the planning process of these structures. In two-meter wave conditions, the tests show that wave height is generally reduced in the sheltered area, which leads to improved safety for beach users (bathing is prohibited when wave height exceeds the two-meter threshold). However, the numerical models also reveal that velocities in the sheltered area usually decrease, which must be controlled to prevent stagnation in the bathing area.     

长江中下游洲滩守护工程概化模型试验研究﹡

为了研究洲滩守护工程的护滩效果及工程实施后局部冲刷坑形态,以长江下游较为典型的洲滩守护工程为例,采用大比尺局部动床概化物理模型试验方法,对鱼骨型间隔式护滩带工程进行了试验研究。根据工程及试验具体情况,详细分析了该试验方法的可行性,并给出了鱼骨型护滩带方案的试验结果。结果表明,该试验方法不但能够较方便地比选不同平面布置的工程方案之间的护滩效果,同时可得到局部冲刷坑的形态参数,对工程设计有较好的指导意义。     

我国水运工程科学研究的现状

经过近年来的快速发展,我国的水运工程科学研究已经达到了较高的水平,但距离工程实际的需求还有很大差距,与国外同行业相比有很多不足。文章总结了淤泥质海岸泥沙运动规律,粉沙质海岸泥沙运动规律,海岸动力及沙质海岸泥沙运动规律,山区河流航道整治技术,平原河流航道整治技术,通航枢纽建设关键技术,水工构造物检测、评估与加固技术,环境保护技术,淤泥质海岸港口适航水深应用技术和水动力数值模拟软件包TK-2D等10个方面的研究现状。总结了现场调查和有关资料分析,理论分析研究,物理模型试验研究和数值模拟研究等4种研究手段的发展现状。目的是促进核心技术的形成,提高为重大工程服务的能力和水平,增强国际竞争力。     

Resilience of Touristic Island Beaches Under Sea Level Rise: A Methodological Framework

This contribution addresses the need for a simple model for managers to employ when planning strategies for the management of touristic beaches under sea level rise. A methodological framework was developed and tested in two Aegean archipelago islands (Lesvos and Rhodes, Greece). The scheme can represent the status of touristic island beaches, based on easily obtained variables/indicators and projections of beach erosion/retreat under different scenarios of mean sea level rise (MSLR) and extreme events. Information on beach geomorphological characteristics, environmental setting, water quality, management, and services (such as those used in the “Blue Flag” classification) was collated/collected and beach erosion/retreat due to CV & C was estimated through suitable ensembles of cross-shore (1-D) morphodynamic models. A Strength-Weaknesses-Opportunities-Threats (SWOT) framework was employed to assist in the selection of indicators and multicriteria analysis used to optimize indicator weights and rank beaches according to their sustainability under sea level rise. Implementation of the framework at the two islands has shown that: the majority of Lesvos and Rhodes beaches (82% of a total of 217 beaches and 58% of a total of 97 beaches, respectively) can be classified as beaches with no, or minimal, human interference, suggesting that under environmentally sound coastal management further touristic development might be afforded; there could be very significant effects of the sea level rise on the carrying and buffering capacities of the most developed (“Blue Flag”) beaches, with some expected even under conservative projections to be completely eroded by 2100, unless technical adaptation measures are taken; and using the proposed framework, touristic beaches can be rapidly ranked in terms of their resilience to sea level rise and their development potential, allowing prioritization of effective management responses.     

漳州南太武海滩泥化综合整治

南太武海滩前部水域浪小流弱,九龙江和近岸陆域排洪排污对海滩直接影响较大,造成严重的沙滩泥化和环境问题。面对复杂的外部边界条件,综合海岸动力学、生态学、环境学等多学科的方法,统筹城市排洪排污需求和景观生态需要,分析沙滩泥化的现状和机理,从技术、经济和生态方面论证了治理方案的可行性,并创新性探索减淤屏在整治海滩泥化工程设计中的应用。     

Assessing the Utility of Beach Ecolabels for Use by Local Management

Ecolabels for beaches have been around since 1985 and have grown rapidly over the past decade. However, effects from ecolabels on beach ecology and local coastal cultures are unknown. This study reviews the literature on tourism ecolabels and environmental certification for beaches, analyzes the criteria of the most prominent beach ecolabel, and identifies considerations and proposes recommendations for local management that address sandy beach ecology and local cultures. The Blue Flag ecolabel is evaluated for how well the program criteria balance tourism, the processes of sandy beach ecology, and accommodate for local cultural values. This Blue Flag's criteria leave out protecting sandy beach ecology and fail to incorporate local community values in program design. The results of the study include three areas that beach managers need to consider for better understanding the utility of beach ecolabel programs: opportunity costs of participation and consequences of losing certification; evaluate investment in multiple certifications; and identify potential changes from the implementation of ecolabels.     

钦州湾围滩工程前后潮流场的数值模拟

基于双时间层的有限差分方法(ADI),建立了水深平均二维浅水潮流数学模型,采用逆风格式和追赶法求解二维浅水方程,通过建立钦州湾二维潮流数值模型重现钦州湾的潮位和潮流变化状况。模拟结果与同步进行的岸边潮位及海上潮流的观测值校验结果表明,实测潮位资料与对应时间的计算结果吻合良好,实测潮流与对应时间的计算结果十分接近。模拟计算结果真实地反映钦州湾的潮位变化和潮流运动状况。钦州湾围滩工程实施前后的潮流场数值模拟研究结果表明该工程建设不会对海域水动力学条件产生较大影响。     

长江上游叉鱼碛滩航道特性及维护对策

叉鱼碛为长江上游过渡段浅滩,位于泸州境内,属于天然河段。2013年向家坝水电站完成蓄水,2015年长江上游航道最小维护水深从2.7 m提高至2.9 m。2016年禁采前由于人为无序的挖砂采石对上游诸多滩段造成较大的破坏,枯水期水流分散,冲刷能力减弱。在诸多背景下,长江上游诸多碍航滩段枯水期航道畅通面临较大的挑战,叉鱼碛滩段为其中的一个代表。根据实测资料分析向家坝水电站蓄水前后水沙条件的变化,对滩段近年来的演变规律进行总结,并且根据近年航道维护疏浚实施情况、疏浚效果以及相关问题,对滩段的航道维护对策进行分析,为滩段养护疏浚的设计、施工提出相关建议以及加抛整治建筑物的治理方案,可为航道维护及航道治理提供技术支撑。     

砂质海滩不透空丁坝特性研究

丁坝是整治海岸侵蚀的主要结构物之一。如何在特定的水动力条件和泥沙条件下建设具有岸线防护功能的丁坝,对整治海岸侵蚀具有重大意义。用数值方法研究丁坝建设后近岸的波浪、水流及泥沙运动,从近坝泥沙输沙率及近坝水流的变化分析探讨丁坝长度与角度的选取,得出不同沙滩坡度、波高、波向下沿坝裂流情况和近坝泥沙运动情况,并给出丁坝长度与角度的选取建议。     

岸滩演变对入江口门航道的影响

各支流入江口门是沟通各支流和长江的关键部位,其河床稳定性对保持航道畅通具有重大作用.选择南京河段梅子洲汉道段秦淮新河口和城南河口为研究对象,分析入江口门岸滩演变特征,并结合入江口门历年疏浚资料,分析岸滩演变对入江口门航道的影响.研究成果表明,岸滩演变不仅形成了入江口门的河道局部条件,并且制约口门的水沙条件,因此,对入江口门的水流、泥沙运动和航道产生重大影响.     

Modeling Potential Impacts of Beach Replenishment on Horseshoe Crab Nesting Habitat Suitability

Beach replenishment has been proposed to increase nesting habitat for horseshoe crabs, but its environmental consequences may compromise the egg development and viability of this declining species. Horseshoe crab habitat requirements were used to build a habitat suitability model in STELLA to predict the potential impacts of beach replenishment on horseshoe crab eggs. A habitat suitability index (H.S.I.) comprised of six variables (dissolved oxygen, sediment grain size, sand temperature, sand moisture, wave energy, and salinity) was developed and compared between replenished and natural beaches. Sediment grain size and dissolved oxygen were higher in the natural beach, whereas sand temperature and moisture were higher in the replenished beach, resulting in significantly higher suitability of the natural beach (p = 5.39 × 10^?15, df = 30). The model was most sensitive to air temperature, rainfall, tide, and sediment grain size. This model is useful for understanding the processes affecting horseshoe crabs and predicting impacts of coastal management activities on habitat suitability. Based on the results of this model, beach replenishment is not recommended for increasing or improving horseshoe crab habitat, unless care is taken to match fill sediment to natural grain size and color.