Beach morphology and change along the mixed grain-size delta of the dammed Elwha River, Washington

Sediment supply provides a fundamental control on the morphology of river deltas, and humans have significantly modified these supplies for centuries. Here we examine the effects of almost a century of sediment supply reduction from the damming of the Elwha River in Washington on shoreline position and beach morphology of its wave-dominated delta. The mean rate of shoreline erosion during 1939–2006 is ~ 0.6 m/yr, which is equivalent to ~ 24,000 m³/yr of sediment divergence in the littoral cell, a rate approximately equal to 25–50% of the littoral-grade sediment trapped by the dams. Semi-annual surveys between 2004 and 2007 show that most erosion occurs during the winter with lower rates of change in the summer. Shoreline change and morphology also differ spatially. Negligible shoreline change has occurred updrift (west) of the river mouth, where the beach is mixed sand to cobble, cuspate, and reflective. The beach downdrift (east) of the river mouth has had significant and persistent erosion, but this beach differs in that it has a reflective foreshore with a dissipative low-tide terrace. Downdrift beach erosion results from foreshore retreat, which broadens the low-tide terrace with time, and the rate of this kind of erosion has increased significantly from ~ 0.8 m/yr during 1939–1990 to ~ 1.4 m/yr during 1990–2006. Erosion rates for the downdrift beach derived from the 2004–2007 topographic surveys vary between 0 and 13 m/yr, with an average of 3.8 m/yr. We note that the low-tide terrace is significantly coarser (mean grain size ~ 100 mm) than the foreshore (mean grain size ~ 30 mm), a pattern contrary to the typical observation of fining low-tide terraces in the region and worldwide. Because this cobble low-tide terrace is created by foreshore erosion, has been steady over intervals of at least years, is predicted to have negligible longshore transport compared to the foreshore portion of the beach, and is inconsistent with oral history of abundant shellfish collections from the low-tide beach, we suggest that it is an armored layer of cobble clasts that are not generally competent in the physical setting of the delta. Thus, the cobble low-tide terrace is very likely a geomorphological feature caused by coastal erosion of a coastal plain and delta, which in turn is related to the impacts of the dams on the Elwha River to sediment fluxes to the coast.     

The effect of sea-level rise in the 21st century on marine structures along the Mediterranean coast of Israel: An evaluation of physical damage and adaptation cost

This study presents estimates of the impact adaptation costs due to damage to coastal and marine structures located along the Mediterranean coast of Israel caused by sea-level rise in the 21st century. The study examines the effects on various types of constructions, including seaports, power plants, marinas, desalination plants, sea walls, detached breakwaters, and bathing beach infrastructures for sea-level rises of 0.5 m and 1 m. To this end, we conduct an analysis of hydrodynamic forces on the structures and an uncertainty analysis of their occurrence. The study find that the impact of wave overtopping of breakwaters can lead to extensive damage to port infrastructure and to the vessels moored inside. Adaptation costs are computed as the corrective measures to be taken to maintain the functionality of the structures.     

Coastal Changes Over the Past 200 Years Around Ovalau and Moturiki Islands,Fiji: Implications for coastal zone management

The islands Ovalau and Moturiki in central Fiji are selected for the investigation of coastal change over the past c. 200 years. Although having coastal environments typical of many tropical Pacific Islands, Ovalau and Moturiki are also atypical because they experienced urban and infrastructural developments before most other parts. The associated records enable recent coastal changes to be discerned more clearly here than has been possible elsewhere. The islands are surrounded by coral reef, the configuration of which accounts for variations in vulnerability of their coasts to erosion. Interviews were conducted in each of 22 settlements along the islands' coasts and information obtained about recent coastal change. Mangroves are concentrated along leeward coasts, although they have been cleared from many windward coasts in the last 40 + years, causing shoreline erosion to be initiated/accelerated. Most shoreline-protection initiatives (vegetation planting and seawall construction) have failed. Three major management implications of the study are discussed. Firstly, there is a need to redefine the nature of the interactions between coastal inhabitants and coastal ecosystems, so that environments are sustainably developed; and specifically that reefs are conserved and shoreline vegetation (especially mangroves) is effectively replanted. Secondly, information about appropriate design and composition of artificial structures for shoreline protection needs to be made available to the local communities who construct most of them. Thirdly, alternative sources of sand and rock aggregate to those whose extraction aggravates shoreline erosion should be sought.     

Geomorphology of the Sub-Antarctic Australian Territory of Heard Island-McDonald Island

The geomorphology of Heard Island-McDonald Island is primarily the product of close interplay between volcanism, glaciation, and vigorous marine processes in a stormy sub-Antarctic environment. The dominant landform is the strato-volcano Big Ben (2745m), which is the highest mountain on Australian territory outside Antarctica. Other volcanic landforms include scoria cones, domes, open vertical volcanic conduits, lava flows and lava tubes. Volcanic activity is ongoing from the summit of Big Ben, and from Samarang Hill on McDonald Island. Early, but unproven, glacial sediments may exist within the Late Miocene - Early Pliocene Drygalski Formation, which forms a 300m high plateau along the northern coast of Heard Island. Growth of the present glaciers, some of which reach sea level, has been a response to progressive growth of the volcanoes. A variety of erosional and depositional glacial landforms is present, including major lateral moraines and extensive hummocky moraines. Vigorous longshore drift and an abundant sediment supply have produced a large spit at the downdrift end of the island, and formed bars from reworked glacigenic sediment that now impound proglacial estuarine lagoons, some of which have grown rapidly over recent decades as tidewater glaciers have retreated. Integrated study of the volcanic, glacial and coastal sequences offers the possibility of constructing a well-dated record of climate change. Research into the geomorphology, surficial sediments, and contemporary geomorphological processes, including glaciofluvial sediment flux, is also important as an aid to environmental management on land, and to management of the adjacent marine environment.     

TRANSFORMATION PATTERNS OF SUBAERIAL MICRO-TIDAL BEACHES

Seven subaerial, low energy beaches in the SE Mediterranean were surveyed biweekly for 13 months. Beach level data were computer-processed and plotted as time-series profile diagrams that differentiated the subaerial beach into three basic subenvironments: backshore, berm, and swash-zone. Heterogeneous seasonal trends in beach sand budget, erosion/accretion patterns, occurrence of ridges and berm-crests, and in pollution by seaborne tar were observed. The profile stations also showed very different degrees of seasonality, although located along similar beaches. Local beachrock protection, when evident, effectively masked seasonality by significantly lowering beach dynamics. Biweekly, seasonal, and annual fluctuations of the beach sand-budget were computed. Average annual net sand flux at the seven beaches was 66 m³/m of beach front, though wide variations occurred. Annual changes in the sand budget along the study area exceeded volumetric changes within the profile, indicating longshore sand transfer. Synchronism of beach behavior prevailed only at the seasonal level. However, intra-seasonal fluctuations for the different profile stations were out of phase, indicating poor synchronism of beach response due to longshore movement of rhythmic topography. Profile changes were thus often unrelated to concomitant wave-climate changes. The overall heterogeneous beach response was in sharp contrast to the identical wave climate, similar bathymetry, and sedimentology of the studied beaches.     

Classification of washover dynamics in barrier islands

This study systematically classifies washover dynamics with reference to coastal changes along the Ria Formosa barrier islands (Southern Portugal). Identification of washovers using a sequence of 11 sets of aerial photographs dated between 1947 and 2001 allowed a classification to be developed based on: (1) overwash evolution (increasing, decreasing, or constant overwash processes); (2) the mechanisms promoting washover formation (exceptional to infrequent oceanographic conditions, washout processes, structural erosion, inlet dynamics, and human interventions); and (3) the mechanisms promoting washover cessation (berm development, structural erosion, dune development, inlet dynamics, and human interventions). A total of 369 different washovers were observed along the Ria Formosa barriers during the study period, with 209 washovers being formed in various types of dune morphology and 303 being obliterated. The number of washovers was relatively stable from 1947 to 1972, and increased dramatically between 1972 and 1976 probably as a result of the development of immature inlet margins and downdrift starvation. From 1976 to 2001, washover occurrences declined and their spatial dimensions decreased, leading to a decrease in overwash activity over this time. Overall, the dominant formation mechanisms of washovers in the Ria Formosa were inlet dynamics (accounting for 57% of washovers formed) and structural erosion (20%), with human intervention mechanisms accounting for 12%. The cessation of washovers was dominated by dune development (33% of the washovers obliterated) followed by inlet dynamics (24%) and structural erosion (19%), while human intervention mechanisms accounted for 13%. The classification should be of use for the coastal management of barrier systems including the definition of overwash-prone areas and the determination of the relative importance of the mechanisms contributing to washover formation and cessation.     

华南港湾海岸的地貌特征

本文根据作者参加华南海岸和港口调查研究的体会,对华南现代海岸的形成条件和港湾海岸的地貌特点进行分析。     

Aeolian sand transport along beaches

Storm‐generated ephemeral transverse sand ridges were observed developing along the beach fronting Sir Richard Peninsula, South Australia during 25 March 1984. The ridges displayed a mean height of 10 cm and a wavelength of 12 m; their breadth was approximately 2 m, and length varied with beach width but ranged up to 40 m over 10 km of coastline. The steeper sides of the ridges faced upwind due to erosion after initial ridge development. Damp sand in the swales inhibited wind scour and restricted sand supply, but provided a firm substrate over which the sand could saltate. Approximately 5000 m³ of sand were incorporated into the ridges by westerly winds blowing at velocities between 45 and 69 km/hr. This observation emphasises the role of alongshore winds in transporting beach sediments and developing essentially ephemeral forms, which might, nevertheless, be preserved in the geological record. The significance of these forms varies with coastal orientation and local wind regimes.     

钱塘江河口治理的成就与展望

阐述了40年来钱塘江河口治理的成就,在涌潮河段束窄整治了64km游荡不定的河道。围垦了90万亩的土地,为国家创造了巨大的财富。但南岸围垦,水流北逼,潮流掏蚀北岸鱼鳞石塘的塘脚,塘石松动,急待修理。鉴于钱塘江北岸的海塘具有保护太湖平原的重要的作用,综合治理北岸海塘至为迫切。对钱塘江北岸标准塘建设计划进行了评价,认为标准塘方案规划有据,目标明显,方案可行,经济合理。展望了钱塘江河口治理并对需要进一步研究的问题进行了探讨。特别是河流近口段与河口段的衔接问题,河口段与杭州湾的衔接问题,以及口内外泥沙交换问题,应该作为重要问题进行重点研究。     

1977-2014年江苏中部滨海湿地演化与围垦空间演变趋势

通过野外实地调研与遥感影像解译相结合的方式,研究1977-2014年（1977、1984、2000、2007与2014年）江苏中部滩涂湿地演化与围垦空间演变的规律。结果表明,1977-2014年江苏中部滨海湿地射阳河口以南岸线段总体以淤长为主,但是也存在侵蚀的岸线段,总体淤长/侵蚀速度在±20 m/yr左右,最高值出现在东台和如东洋口港附近。研究区湿地围垦的速度远高于岸线淤长的速度,基本维持在50 m/yr以上。1977-2014年江苏滨海湿地的生态关键区面积出现了快速的退化趋势,特别是盐生植被空间的快速萎缩,主要出现在射阳南部和大丰市。调查发现研究区传统的湿地围垦开发演变模式是光滩→盐生植被→养殖水面→耕地→建设用地。但是现在由于新技术和新方法的应用,极大地缩短了围垦演变路径和周期,有助于围垦经济效益的提高。江苏滨海湿地围垦后土地开发利用强度呈较为明显的上升趋势。同时,江苏滨海湿地开发的热点空间在区域上主要集中于几个重要的港口及其腹地建制镇附近,但总体规模不大。     

Remote sensing-based assessment of tsunami vulnerability and risk in Alexandria, Egypt

Tsunamis can cause catastrophic loss of life, destruction of property, engineered structures and coastal infrastructure, and they can lead to major economic losses. Even though tsunamis are relatively rare in the Mediterranean Sea, their potential danger to cities along the Mediterranean coast cannot be neglected. In order to create awareness among the potentially affected people it is important to know the risk and vulnerability of the population and infrastructure related to a possible tsunami impact. In this work a hazard, vulnerability and risk analysis for buildings in two districts of Alexandria was carried out. Relevant input parameters were derived mainly from remote sensing and field data and were analyzed with a geographical information system (GIS). Based on historical records of past tsunamis, two inundation scenarios of 5 m and 9 m were defined and modeled applying a bath-type model. The resulting tsunami building risk zone maps showed that 12% of the buildings in El Gomrok district are at high or very high risk for the 5 m scenario, while the risk for El Montazah area is low. For the 9 m scenario, on the other hand, the majority of the buildings in both districts, 56% of El Gomrok, and 60% of El Montazah, are in the high or very high risk zone. An analysis of the building use indicated that the majority of these buildings are residential and commercial types, highlighting that the potential consequences of a tsunami could be severe. Due to the scarcity of historical data no frequency could be associated with the two selected scenarios. While both are credible we consider the 5 m scenario as possible but unlikely and the 9 m scenario as unlikely.     

Soil erosion along a long slope in the gentle hilly areas of black soil region in Northeast China

Characteristics of soil erosion change along a long slope in the gentle hilly areas in black soil region in Northeast China are discussed. A simplified slope model based on seg-ments was used to analyze the runoff data and soil erosion data observed between 2003 and 2004 over 10 field plots with different slope length in Heshan Farm, Heilongjiang Province. We found that soil erosion rate over long slopes in the black soil region changed alternatively along the slope and creates alternative zones of intensive erosion and week erosion.The exact place of each zone is different for different rainfall conditions. In a year with less and mild precipitation, rill cannot happen within the top 50 m, while in a year with large and inten-sive precipitation, rill can be formed starting even at 15 m from the top of the slope.     

江苏海岸侵蚀过程及其趋势

江苏省侵蚀海岸的总长度为 30 1 7km ,分为 4段 :废黄河三角洲海岸、港海岸、吕四海岸以及海州湾的沙质海岸。各段海岸侵蚀原因不同。废黄河三角洲海岸是因黄河改道失去泥沙来源 ;吕四与港海岸则因辐射沙洲调整过程中滨岸水道的向岸移动造成的 ;而北部沙岸则是因人类活动 (上游建设水库及开挖海滩沙 )的干扰。江苏海岸是一个沉积物准封闭系统 ,全球性海平面上升将加剧这一侵蚀过程 ,预计未来侵蚀海岸的长度将增加 ,辐射沙洲区的外围沙洲将因侵蚀而向中心区退缩。一些目前是隐型侵蚀的岸段将向显性侵蚀的阶段发展。由于连云港到长江口北支的岸段是软性海岸 ,缺乏硬质节点 ,在没有建造大型人工设施的前提下 ,估计江苏海岸动态及制定开发规划时必须考虑平直化的大趋势。     

Protecting an eroding shoreline: the evolution of management response

Sandy Hook. New Jersey, was used by the US Army until 1970 for coastal defence installations at the entrance to New York harbour and as an ordnance proving ground. Since 1970, Sandy Hook has been managed by the US National Park Service as a part of Gateway National Recreation Area. An important problem which managers of both institutions have had to face is the instability of the narrow neck of the spit. The high rates of erosion which have predominated at the neck have jeopardized the overland access route to the facilities at the northern end of the spit, and both Army and Park Service managers have taken steps to alleviate the problem. A breach in the neck in 1896 led the Army engineers to construct a seawall to close the breach and to protect the access road. Over the next 30 years, several projects were undertaken to extend the length of the seawall and to reinforce the structure. The Park Service managers are currently facing the same problem, although the focus of erosion has been transferred northward. The National Park Service has chosen a more dynamic solution to the problem in accordance with their objectives for this eroding area. This study demonstrates that the protection approaches selected for use by the managers of both institutions were a function of differing objectives. In addition, the study provides an example of how management decisions made in the past influence present management actions.     

Theoretical constraints and chronological evidence of Holocene coastal development in central and southern New South Wales, Australia

Holocene coastal evolution in New South Wales has been interpreted essentially as the unfolding of the impact of marine transgression. Sea level on this coast supposedly reached its present height at 6–6.5 ka, and varied < 1 m since then. The early Holocene rise of the sea has been considered the key factor (“forcing function”) in dune migration, coastal sand barrier development, and the evolution of estuaries. Episodic storminess during the late Holocene has been seen as an important, though secondary, factor in beach erosion and dune mobilisation. An alternate interpretation presented here challenges the concept of the marine transgression as the primary “forcing function”. It (a) attributes early Holocene dune mobilisation to climate rather than the rising sea; (b) shows that the sea reached its present level by 7 ka and rose to at least + 2 m until 1.5 ka; (c) links late Holocene dune activity to local disruption of vegetation rather than to regional episodic storminess; (d) demonstrates a fall of 2°C in sea surface temperature after 3 ka that coincides with the onset of barrier erosion; (e) recognises the imprint of at least three tsunamis in the coastal sedimentary record.     

Causes and Effects of Coastal Sand Mining in Ghana

Sand mining is a type of open-cast mining that provides material for the construction sector in Ghana. The construction sector in the coastal areas of Ghana relies heavily on coastal sand and pebbles in the building of houses, bridges and roads. Its contribution to Ghana's industrial output has increased from 17.4 per cent in 1986 to 20.8 per cent in 1993. However, the process of sand mining has accelerated coastal environmental degradation to an alarming rate in many areas. As a result the government has been compelled to spend millions of dollars to combat sea erosion. This paper examines the causes and effects of coastal sand mining in three communities in the Ahanta West District of Ghana. It argues that coastal sand needs to be exploited to satisfy human demands but this requires efficient and effective resource management to ensure sustainable development. It also calls for a concerted effort by policy makers, sand contractors, engineers, traditional rulers and local residents to find a solution to the coastal environmental crisis.     

沙石质建筑垃圾不同覆盖方式防风固沙效益

为了解沙石质建筑垃圾不同覆盖方式防风固沙效益,在野外对不同覆盖方式的风蚀风积量、风沙流特征、土壤水分、植被生长状况进行了观测研究。结果表明：（1）不同覆盖方式年风蚀量较流沙减少了91%以上,其中平铺覆盖方式固沙效果好于带状和方格覆盖方式。平铺覆盖方式和流沙风沙流结构呈幂、指数函数分布,带状、方格覆盖方式呈多项式函数分布;（2）不同覆盖方式较流沙显著提高了土壤容积含水率（P<0.05）,平铺方式保水效果好于方格和带状覆盖方式。覆盖度30%平铺、1.5 m×1.5 m方格和宽1.5 m带状土壤各层平均容积含水率比流沙分别提高了3.1%、2.8%和1.5%;（3）不同的覆盖方式较流沙显著增加了植被盖度（P<0.05）,其中平铺方式群落多样性指数最高。覆盖度30%平铺植被盖度较流沙提高了5%。1.5 m×1.5 m方格覆盖方式植被群落多样性指数最低,植被盖度最高,较流沙提高了14%。     

Assessment of coastal vulnerability to environmental change in Jiangsu coastal plain

Assessment of coastal vulnerability to future environmental change has been emphasized in coastal nations or regions. The Jiangsu coastal plain, located to the north of the Yangtze River Delta in China, is most vulnerable to sea level rise and exacerbating coastal hazards. This paper develops the method of delimiting vulnerable scope and assessing coastal vulnerability through field observations and sampling and by applying remote sensing and GIS, which are suitable for great river delta and coastal plains with large area, relative complex micro-geomorphology and the protection of seawall. Applying this method, the coastal vulnerability of the Jiangsu coastal plain to relative sea level rise (approximately 50 cm up to the year 2050) and exacerbating storm surges have been assessed. The results show that, up to the year 2050, the Jiangsu coastal plain will probably lose 12.8 % of tidal flats (about 5.8×104 hm2) and 7.9 % of cultivated land (about 7.2×104 hm2). Meanwhile, 2.0 % of population, 3.8 % of original value of fixed assets, 3.2% of GDP (Gross Domestic Product), 40.3 % of salt industry and 5.8 % of aquiculture respectively will be affected due to coastal environmental change.     

AEOLIAN BLOWOUT DYNAMICS IN SUBARCTIC LAPLAND BASED ON DECADAL LEVELLING INVESTIGATIONS

Aeolian processes in the subarctic ecocline were investigated by measuring present‐day erosion and deposition rates over a decade in blowouts scoured into stabilized Early to Mid‐Holocene dunes. Four localities from different vegetation zones in Finnish Lapland were surveyed using precision levelling (infrared tachymeter) along eight transects at 1‐m intervals. During an 11‐year observation period, a total of 1439 observation points were monitored in three measurement campaigns, in 1993, 1994 and 2004. Together with dating results reported elsewhere, the results demonstrate the relative quiescence of these subarctic blowouts compared to many coastal dunes. On average, the deflation rate of the studied basins was 8.8 mm a^‐1, which corresponds well with the age and depth of the blowouts. Net deposition had taken place at 30% of the observation points, and one of the eight studied transects showed net deposition as the transect average. Symmetrical, smooth basins showed more consistent changes than basins with a complex form, indicating that internal factors are important in blowout formation under the Lapland climatic range. The deepest part of a blowout was generally found in the upwind end. The erosion/deposition patterns of the transects over a one‐year monitoring period were interpreted with Fourier analysis revealing along‐transect cyclicity, possibly reflecting the movement of small migrating bedforms in the blowouts. Generally, deflation rates at the latitudinal pine forest line were smaller than at those well outside the pine forest suggesting that the coniferous forest at the subarctic ecocline affects the intensity of present‐day aeolian activity in Fennoscandia.     

Coastal processes and cliff recession between Gabicce and Pesaro (northern Adriatic Sea): a case history

Cliff recession on the high rocky coast between Gabicce and Pesaro Adriatic sea causes a wide range of mass movement processes on the whole slope, affecting both the bedrock and the overburden. The outcropping late Miocene rock formations are represented by marls, marly limestones, dark laminated mudstones and bedded sandstones and marls. Mass movements are common because of stratification and discontinuities in the rocks that, together with the presence of groundwater and weathering processes, reduce the overall strength of the slopes. A model for the evolution of this coastal area is proposed, which involves cyclic basal erosion, followed by mass movement that favours debris accumulation at the base of the cliff. The longshore currents have to then remove the material before a new cycle can begin.