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1.
Exposed sandy beaches filter huge volumes of sea water daily as a result of wave and tide action. A regression model is developed which predicts the volume of water filtered daily by a beach as a function of tide range, beach slope and sand particle size. From these parameters estimates are also made of intertidal distance, the degree of expansion of the intertidal above the still water tide range by wave action and the average path length through the sand interstices percolated by filtered sea water. An equation is derived relating the degree of mineralisation of organic matter in the filtered sea water to the distance filtered through the sand and the sand particle size. Employing all this information, a simple model is used to estimate the volumes of sea water filtered and the amounts of inorganic nitrogen regenerated by intertidal sandy beaches over a range of physical conditions. The implications of this nutrient generation for the inshore zone are discussed.  相似文献   

2.
On the basis of various lines of evidence, mostly coming from exposed sandy beaches in Southern Africa, it is postulated that under certain conditions high energy sandy beaches and their adjacent surf zones may function as viable ecosystems. Where surf zones are reasonably broad and shallow, cellular circulation patterns predominate and these tend to retain nutrients generated by the macrofauna and interstitial fauna of the beach. These nutrients may then cause blooms of surf zone phytoplankton which in turn serve as food for macrofauna filter feeders. With the perimeter of the circulation cells of the surf zone forming its marine boundary, the beach and surf zone may together be considered an ecosystem with surf phytoplankton the primary producers, beach macrofauna the consumers and interstitial fauna the decomposers.  相似文献   

3.
《Coastal Engineering》2006,53(4):349-362
This paper provides information on the experimental set-up, data collection methods and results to date for the project “Large scale modelling of coarse grained beaches”, undertaken at the Large Wave Channel (GWK) of FZK in Hannover by an international group of researchers in Spring 2002. The main objective of the experiments was to provide full scale measurements of cross-shore processes on gravel and mixed beaches for the verification and further development of cross-shore numerical models of gravel and mixed sediment beaches. Identical random and regular wave tests were undertaken for a gravel beach and a mixed sand/gravel beach set up in the flume. Measurements included profile development, water surface elevation along the flume, internal pressures in the swash zone, piezometric head levels within the beach, run-up, flow velocities in the surf-zone and sediment size distributions.The purpose of the paper is to present to the scientific community the experimental procedure, a summary of the data collected, some initial results, as well as a brief outline of the on-going research being carried out with the data by different research groups. The experimental data is available to all the scientific community following submission of a statement of objectives, specification of data requirements and an agreement to abide with the GWK and EU protocols.  相似文献   

4.
The effects of stranded oil from a tanker collision off the South African coast on the meiofauna ratio and density have been monitored over a period of 1 year on two sandy beaches. The perturbation of two beaches was judged against reference beach meiofauna density behaviour. In the undisturbed beach, oil deposited in sediment depressed harpacticoid copepod numbers, while numbers of nematodes stayed similar to those of the reference levels. Removal of surface sand in the mechanically disturbed beach had a greater influence on the density of animals than oil. Both beaches showed recovery after six months, but evidence of pollution by oil of unknown origin was found.  相似文献   

5.
Escalating pressures caused by the combined effects of population growth, demographic shifts, economic development and global climate change pose unprecedented threats to sandy beach ecosystems worldwide. Conservation of beaches as functional ecosystems and protection of their unique biodiversity requires management interventions that not only mitigate threats to physical properties of sandy shores, but also include ecological dimensions. Yet, beach management remains overwhelmingly focused on engineering interventions. Here we summarise the key outcomes of several workshops, held during the 2006 Sandy Beach Ecology Symposium in Vigo, Spain, that addressed issues of climate change, beach management and sampling methodology. Because efficient communication between managers and ecologists is critical, we summarise the salient features of sandy beaches as functional ecosystems in 50 'key statements'; these provide a succinct synopsis of the main structural and functional characteristics of these highly dynamic systems. Key outcomes of the workshops include a set of recommendations on designs and methods for sampling the benthic infaunal communities of beaches, the identification of the main ecological effects caused by direct and indirect human interventions, the predicted consequence of climate change for beach ecosystems, and priority areas for future research.  相似文献   

6.
Sandy beaches, prime recreational assets that attract more people than other types of shorelines, are the main assets underpinning many coastal economies and developments. However, the intense stressors to the ecology of sandy beaches caused by recreational activities are generally underestimated or ignored. This study was the first to emphasize the ecological characteristics of recreational beaches in China and assess the response of macrobenthos at Liandao Beach, a typical sandy beach in the central part of China. Using the Before/During/After/Control/Impact (BDACI) method, differences in multiple variables (species richness, mean density, diversity) between a heavily recreationally impacted transect (TrH/Impact) and a less-impacted transect (TrL/Control) in different impact periods (Before, During & After) were applied to assess the response of sandy-beach macrobenthos to recreation and tourism. Meanwhile, a comparison between the macrobenthos conditions of the studied beach and reference conditions calculating from historical data of similar beaches with little recreation and tourism disturbances was carried out. Furthermore, the quality control chart approach was used to detect in detail the macrobenthos stable state and yearly response to recreational activities. The results showed that recreation and tourism posed a serious threat to the beach ecosystem; macrobenthos on the studied beach were seriously disturbed by recreational activities, and their variations were highly negatively related to the human recreational level. After monthly recreational impacts, the macrobenthos decreased sharply and recovered with difficulty during 1 year. Over the long-term, the macrobenthos had a sharp decreasing trend, which indicated that the ecological environment of the beach was highly disturbed. Conservation measures for recreational beaches are very challenging because of the economic value and popularity of sandy beaches as recreational sites. However, practicable conservation measures could be implemented that prevent or slow ecological degradation. A number of management and conservation suggestions are put forward, such as the establishment of the ecological carrying capacity of Liandao Beach in terms of direct recreational use, creation of themed exhibitions related to the beach macrobenthos and beach ecosystem and dissemination of this knowledge to visitors, implementation of spatial zoning of beach use, visitor management and environmental education.  相似文献   

7.
Abstract. Eight sandy beaches were seasonally sampled along the coast of Chile, from ca. 21 to 42° S (about 3000 km) to study the relationship between community structure of the intertidal macroinfauna and beach characteristics. Sediment samples (0.1 m2, 30 cm deep) were collected (July – September 1998 and December 1998 – January 1999) with plastic cylinders at 15 equally spaced levels along three replicated transects extending from above the drift line to the swash zone. The sediment was sieved through a 1 mm mesh and the organisms collected stored in 5 % formalin. To define beach types, Dean's parameter (Ω) was calculated from wave heights and periods, and fall velocity of sand particles from the swash zone. Crustaceans (mainly peracarids) were the most diverse group with 14 species, followed by polychaetes with 5 species. The talitrid amphipod Orchestoidea tuberculata , the cirolanid isopods Excirolana braziliensis and E. hirsuticauda and the anomuran decapod Emerita analoga were the most widely distributed and common species. Regression analyses between species richness, abundance and biomass of the whole macroinfauna versus sediment characteristics, beach face slopes and morphodynamic beach states showed no significant relationships. Thus, macroinfaunal community characteristics did not increase linearly from lower intermediate to higher intermediate or dissipative beach states as had been found before in Chile or in other coasts. A comparative analysis with data from sandy beaches of other world regions showed that the number of species inhabiting Chilean sandy beaches was generally lower, whereas total population abundances were generally higher compared with values reported elsewhere.  相似文献   

8.
砂质海滩的形成与发育是联系地壳深部过程和地表过程的综合体现．本文根据中国沿岸砂质海滩分布状况调查结果,通过分析其分布规律与中国东部沿海中新生代构造地质分区不同海洋沉积环境的内在联系,探讨了砂质海滩区域性差异分布和堆积地貌的成因特点,从而为我国海岸资源利用的宏观配置和管理提供科学依据．研究得出：（1）中国沿岸砂质海滩的形成与发育受中新生代地质构造带控制,尤其受新构造期地壳断块升降活动差异性的影响,呈现出区域性富集的格局．（2）中国砂质海滩基本形成在构造隆起带岬湾沿岸,并且富集在其中新构造期处于上升区的海岸,这主要在于其区域性海岸环境具有形成砂质沉积的物质基础．（3）构造隆起带滨海泥沙的输沙途径及其再分配形式复杂多样,从而产生了各种不同的砂质海滩堆积地貌类型．（4）根据海岸地貌和沉积成因模式,将中国沿岸砂质海滩划分为岬湾海岸叠置沙体沉积形式、滨外坝沙体连续沉积形式和浪控三角洲平原岸改造沉积形式等3种基本模型．（5）沿海晚第四世纪古夷平地貌面与现代海平面相对高程分布的分析表明,山丘岬湾岸型砂质海滩主要形成在新构造运动下沉区段或构造相对稳定区段,而台地岬湾岸型和泻湖一沙坝岸型形成在上升区段,浪控三角洲平原岸型则分布在断块盆地．  相似文献   

9.
The macrobenthos of two exposed tropical sandy beaches in Rio de Janeiro (Brazil) were compared in relation to density, species richness, and vertical zonation. Biological and sediment samplings were carried out in the austral winter of 2002 and the austral summer of 2003. The sampling design consisted of 10 transects perpendicular to the water line, evenly divided into strata. A sampling unit was taken in each stratum with a 0.04 m2 quadrat sampler. Beaches were also compared according to physical features, such as slope, wave period, wave height, and grain size. According to Dean's Ω morphodynamic index the Pontal is a dissipative beach while the Costa Azul is a reflective one. The mean grain size ranged from median to coarse sand in Costa Azul, whereas in Pontal it ranged from median to very fine sand. Eleven species were collected in the two beaches. Crustaceans were the dominant in the Costa Azul Beach, while the polychaete Scolelepis squamata dominated the Pontal beach. A negative correlation was found between the density of the macrobenthos and mean grain size, and beach slope. On the other hand, the Dean's parameter correlated positively with faunal density. Based on the results of ANOSIM, in both beaches, two groups of stations were identified, defining an upper and a lower beach zone along the vertical distribution of the macrobenthos.  相似文献   

10.
《Ocean Engineering》2004,31(11-12):1351-1375
Sorting of sediment on a beach under wave action takes several forms. Stratified layers of finer and coarser sediment, which depend on wave climate, grain size and beach slope are formed. This complex problem can be simplified by defining the cross-shore and longshore sorting according to the angle between the breaking wave and the coast. In the present study, longshore distribution of sediment as well as corresponding beach profiles was measured in a wave basin. Three-dimensional hydraulic model experiments were performed with regular waves. Eighteen sets of experiments performed in longshore sorting mechanism using two different sand beds. The sorting of the bed material and the formation of armour coats along the beach were defined by grain size distributions and dimensionless parameters for sandy beaches.The rate of sediment transport with grain size sorting was measured in a wave basin. A method introduced sorting process was presented in this study. The sediment rate based on sorting mechanism was also discussed with known methods. It has been found that the non-uniformity of the grain size and hence sorting of the beaches play a very important role in the sand transport due to wave motion in a similar way to the case of steady flow in alluvial channels.  相似文献   

11.
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   

12.
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   

13.
It is known that the fauna of the exposed sandy beaches are primarily controlled by physical variables; but how these variables operate along and across the beach still remains fairly under discussion. In our study, we sampled a range of exposed sandy beaches along the Northwest coast of Spain to determine the relationship between the principal physical variables of the beaches (including beach morphodynamic state), and the macrofaunal community. The fauna of these beaches comprise truly marine species along the intertidal zone as well as semi-terrestrial species in the upper and supratidal environments. These two groups respond in a different manner to the physical environment. The first group is directly controlled by the morphodynamic state of the beach, and variations in the physical environment; the second group is not clearly affected by these physical conditions. In this case, other variables such as food availability and the human uses of the upper limits of the beach seem to be more relevant in explaining the patterns observed in the macrofaunal community.  相似文献   

14.
Sandy beaches have been identified as threatened ecosystems but despite the need to conserve them, they have been generally overlooked. Systematic conservation planning (SCP) has emerged as an efficient method of selecting areas for conservation priority. However, SCP analyses require digital shapefiles of habitat and species diversity. Mapping these attributes for beaches from field data can take years and requires exhaustive resources. This study thus sought to derive a methodology to classify and map beach morphodynamic types from satellite imagery. Since beach morphodynamics is a strong predictor of macrofauna diversity, they could be considered a good surrogate for mapping beach biodiversity. A dataset was generated for 45 microtidal beaches (of known morphodynamic type) by measuring or coding for several physical characteristics from imagery acquired from Google Earth. Conditional inference trees revealed beach width to be the only factor that significantly predicted beach morphodynamic type, giving four categories: dissipative, dissipative-intermediate, intermediate and reflective. The derived model was tested by using it to predict the morphodynamic type of 28 other beaches of known classification. Model performance was good (75% prediction accuracy) but misclassifications occurred at the three breaks between the four categories. For beaches around these breaks, consideration of surf zone characteristics in addition to beach width ameliorated the misclassifications. The final methodology yielded a 93% prediction accuracy of beach morphodynamic type. Overlaying other considerations on this classification scheme could provide additional value to the layer, such that it also describes species’ spatial patterns. These could include: biogeographic regions, estuarine versus sandy beaches and short versus long beaches. The classification scheme was applied to the South African shoreline as a case study. The distribution of the beach morphodynamic types was partly influenced by geography. Most of the long, dissipative beaches are found along the west coast of the country, the south coast beaches are mostly dissipative-intermediate, and the east coast beaches range from short, estuarine pocket and embayed beaches in the former Transkei (south east), to longer intermediate and reflective beaches in KwaZulu-Natal (in the north east). Once combined with the three biogeographic regions, and distinguishing between estuarine and sandy shores, the South African coast comprised 24 different beach types. Representing shorelines in this form opens up potential for numerous spatial analyses that can not only further our understanding of sandy beach ecology at large spatial scales but also aid in deriving conservation strategies for this threatened ecosystem.  相似文献   

15.
The Gold Coast sandy beaches of Queensland (Australia) are exposed to energetic wave conditions. Storms, particularly tropical cyclones, have a high potential of destruction. The Gold Coast has not experienced excessive erosive events over the past 30 years. However, some climate indicators suggest that cyclone frequency is likely to increase in response to global climate change within the near future. Over a 2-month period in early 2006, beach surveys were undertaken with a theodolite total station at four different sites. Offshore wave conditions were provided by SWAN regional wave modelling. During this study, the Gold Coast was exposed to three major storms, the first one being the second most energetic over the past 30 years. Results show a substantial variability of the beach response to these events along the Gold Coast, and that engineering structures do not have marked effects. Easterly swells have the greatest impact on the Gold Coast sub-aerial beach morphology. When low wave-energy conditions prevail, the southern Gold Coast beaches recover more quickly than the northern ones, as they are sheltered from high SE waves and draw advantage from the artificial sand bypassing system. Nevertheless, the data show that the Gold Coast beaches are exceedingly fragile. For instance, the early March decadal event considerably weakened the beaches, which resulted in surprisingly high erosion rates all along the Gold Coast during the two following annual wave events. This study suggests that the Gold Coast beaches would not be able to withstand the impact of an increased frequency of extreme events similar in scale to those of 1967.  相似文献   

16.
1.Introduction Long shorecurrenthasbecomethesubjectofextensiveworldwideresearchformanyyears.The purposeofthestudyistounderstandandpredicttheprocessesofsedimenttransport,shorelineevolu tionandpollutanttransportinthenear shorezoneundertheactionofwaves.Goda(2001)regarded thesuspendedsedimentastheprincipalloadinsedimenttransportandtheeffectoflong shorecurrents wasemphasized.Theeffectofwavesonpollutanttransportwasstudiedbynumericalmodelandfield experiment(TaoandHan,2002;Rodriguezetal.,1995),andth…  相似文献   

17.
The Interstitial Environment of Sandy Beaches   总被引：1，自引：0，他引：1  
Anton  McLachlan Ian  Turner 《Marine Ecology》1994,15(3-4):177-212
Abstract. The interstitial system of sandy beaches is lacunar and has its dimensions defined by the sand granulometry. It can be described by features such as pore size, porosity, permeability, and water content. The most important process occurring in this system, water filtration, is driven by inputs of freshwater from groundwater discharge, and inputs of seawater by tides, wave run-up, and subtidal wave pumping. Reflective beaches have seawater input effected mainly by waves; they filter large water volumes with short residence times. Dissipative beaches display the opposite patterns, slowly filtering small volumes input by tides. Flow patterns and their effects on interstitial climate are described. The water table of the beach moves in response to groundwater discharge, tides, and waves and influences erosion/accretion processes on the beach face: a high water table promotes erosion. A series of moisture zones can be recognised from the dry surface sand at upper tide levels, to permanently saturated sand below the low tide water table, namely: a stratum of dry sand, a stratum of retention, a stratum of resurgence, and stratum of saturation. Interstitial chemistry is briefly described in terms of salinity changes, organic loads, oxygen content, and nutrient cycling. It is concluded that the interstitial environment of sandy beaches spans a continuum between physically and chemically controlled extremes: the former condition occurs on coarse sand reflective beaches, which experience low organic inputs and high filtration rates of large water volumes — resulting in powerful hydrodynamic forces; the latter occurs on dissipative beaches of fine sand, which are subject to high organic inputs and low filtration volumes — resulting in stagnation and steep vertical chemical gradients. Many intermediate situations occur and these are more favourable to interstitial life than either of the extremes.  相似文献   

18.
人工海滩研究进展   总被引：11，自引：0，他引：11  
海滩是激浪作用下泥沙在激浪带的堆积,是海岸带最活跃的地貌单元。近年来,由于世纪性的海平面上升,侵蚀型海滩范围扩大,侵蚀加重,海滩宽度变窄、坡度变陡和滩面物质粗化等问题日益严重,引起了广泛关注,亦成为海岸工程研究的热点课题之一。几十年的工程实践表明,海滩喂养与人工海滩是当前防护海滩侵蚀最有效的措施,并已为欧、美、日等国广泛应用。利用海岸地貌学原理方法,借鉴模拟环境条件类似的周边自然海滩的形成和演变规律,合理的设计海滩物质的颗粒大小和组成,海滩的坡度、高度、宽度以及填砂范围等关键参数,能够有效地使人工海滩更快的达到平衡状态并维持其稳定。在海滩的娱乐休闲功能在国际范围内日益受到重视的今天,这一方法在海岸工程应用上具有重要的现实意义。  相似文献   

19.
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   

20.
Surf zones are highly dynamic, physically stressful parts of sandy beach ecosystems. The high wave energy of surf zones has in the past severely hampered ecological surveys of these systems. Here we used a novel technique to collect fauna from this environment along the Dutch coast. A large vehicle in the form a tripod that drives along the sandy seafloor and supports a sampling platform 11 m above the water line can collect both infaunal (grabs) samples and pull beam trawls for epibenthos. The distribution and diversity of macrofauna were studied at different depths in the surf zone along the Dutch coast. Species diversity and abundance increased with increasing depth of the water column. This increase was especially noticeable on the seaward side of the outer breaker bar. Within the surf zone, in the trough between the two breaker bars, there were spots of high diversity and abundance of macrobenthic infauna. Moreover, the area is also important for epibenthic and fish species, like the commercially important flatfish sole. Spatial patterns of species richness and abundance across an onshore-offshore gradient from the beach to seawards of the breakers suggest the presence of faunal zonation in this environment. The high abundance recorded in troughs was primarily caused by patches of juvenile Sand mason Lanice conchilega. The management implications of these results are that we suggest to protect the surf zone, including the trough between the two breaker bars, as a potential area of high diversity and abundance and to reconsider the objectives of the EU-Habitat Directive and the Water Framework Directive for the coastal area.  相似文献   

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