Shoreline oscillation of Dhanushkodi,Rameswaram, India     

Usha Natesan  R. Vishnunath  K. Kathiravan 《国际地球制图》2015,30(5):520-531

Rameswaram Island located on the southeast coast of India bounded by Gulf of Mannar (GoM) on the south and Palk Bay (PB) on the north, respectively, is unique in nature. The southeastern part of Rameswaram Island known as Dhanushkodi foreland is a long sand spit of about 20?km length. Shoreline erosion/accretion rates are computed based on End-Point Rate, Linear Regression Rate and Net Shoreline Change from Indian Remote sensing Satellite, Linear Imaging Self scanning Sensor III images from 1998 to 2012. Along the PB coast of Dhanushkodi foreland, eroding shorelines are dominant except Arichamunai, whereas it is reversing along GoM. Inter-annual shoreline change revealed that changing trend and stability of Island are affirmed with statistical approaches. An equilibrium shoreline trend is noticed on both the sides of Dhanushkodi foreland. Annual shoreline change rate indicates erosion and accretion in northern and southern coastline of Dhanushkodi foreland varies, respectively.  相似文献   

Shoreline erosion: a cautionary note in using small farm dams to determine catchment erosion rates     

Sara D. Lloyd  Paul Bishop  Ivars Reinfelds 《地球表面变化过程与地形》1998,23(10):905-912

Data from 10 small farm dams in SE Australia show that shoreline erosion due to farm livestock access to the dams can account for a significant proportion (up to 85%) of sediment contained in the dam. The volumes of sediment resulting from such shoreline erosion may be of the same order as the volumes produced by gully erosion in the dams' catchments, prompting caution in using farm dams to which livestock have access to determine small catchment erosion rates. Other issues, related to the trap efficiency, also mean that erosion estimates based on farm dam sedimentation should be treated with caution. © 1998 John Wiley & Sons, Ltd.  相似文献   

Accommodation and sediment-supply controls on clastic parasequences: A meta-analysis     

Luca Colombera  Nigel P. Mountney 《Sedimentology》2020,67(4):1667-1709

This study combines data from many published case studies to undertake a quantitative characterization of clastic parasequences, with the aim to determine how accommodation, sediment supply and autogenic sediment-storage dynamics are recorded in their sedimentary architecture and stacking patterns. Results of this study are used to critically evaluate the validity of paradigms and models that are routinely used to explain and predict trends in the anatomy and arrangement of parasequences. Data on 957 parasequences from 62 case studies of clastic, shallow-water successions were coded in a relational database, which includes outcrop and subsurface datasets of ancient and Quaternary examples. These units cover the preserved records of both river-dominated deltas and wave-dominated coasts, representing shoreline transits over a breadth of timescales, likely of both local and regional extent. The role of extant accommodation, rates of creation of accommodation and rates of sediment supply in determining parasequence architecture is assessed through analysis of relationships between: (i) proxies of these variables at different scales (rates of aggradation and progradation, facies-belt shoreline trajectories, systems-tract type, parasequence-set stacking patterns, parasequence progradation angle and stratigraphic rise, size of feeder rivers); and (ii) parameters that describe the geometry and stacking style of parasequences, and associated shallow-water sand bodies. Statistical analyses of database outputs indicate which proxies of accommodation, sediment supply and accommodation/sediment-supply ratio are significant as predictors of parasequence architecture, and allow for interpretations of the importance of allogenic and autogenic factors. The principal results of this study reveal the following: (i) parasequence thickness varies as a function of water depth, accommodation generation and erosional truncation, and these variations are also reflected across types of systems tracts and parasequence sets; (ii) the dip length of parasequence sand bodies demonstrates scaling with measures of accommodation/sediment-supply ratio at multiple scales, partly in relation to the possible effect of sediment supply on progradation rates; (iii) in systems tracts, stratigraphic trends in parasequence stacking due to autogenic mechanisms or to acceleration or deceleration in relative sea-level fluctuations are not revealed quantitatively; (iv) some association is seen between the abundance of deltaic or river-dominated parasequences and progradational stacking; (v) positive but modest correlation is observed between measures of river-system size and the dip length of shallow-marine parasequence sand bodies. The resulting insights can be applied to guide sequence stratigraphic interpretations of the rock record and the characterization of sub-seismic stratigraphic architectures of subsurface successions.  相似文献   

Oil persistence on beaches in Prince William Sound - a review of SCAT surveys conducted from 1989 to 2002     

Taylor E  Reimer D 《Marine pollution bulletin》2008,56(3):458-474

In 2002, 13 years after the Exxon Valdez oil spill (EVOS), 39 selected sites in Prince William Sound (PWS) were re-surveyed following established shoreline cleanup assessment team (SCAT) field observation procedures to document surface and sub-surface oiling conditions in shoreline sediments and to compare results with those from previous Shoreline Cleanup Assessment Team (SCAT) surveys and other surveys in PWS. The selected sites are locations where EVOS oil persisted in 1992, at the time the Federal and State On-Scene Coordinators determined that the cleanup was complete and that further cleanup activities would provide no net environmental benefit. These sites had been included in a 2001 NOAA survey of shoreline oiling conditions and account for 88% of the sub-surface oil residues (SSO) oil documented by that study. The 2002 field survey found isolated occurrences of residual EVOS surface oil residues (SO) in the form of weathered asphalt pavement at 15 of the 39 sites. This residual SO typically consisted of asphalt in mixed sand/gravel substrate, located within a wave shadow effect created by boulders or bedrock in the upper intertidal to supratidal zone. Residual SO, expressed as a continuous oil cover, was less than 200 m(2) within the approximately 111,120 m(2) surveyed. A total of 1182 pits were dug at locations where SSO residues were present in 1992. Six of the 39 sites and 815 (68%) of the pits contained no residual SSO. Eighty-three percent of pits with SSO residues were found primarily in middle to upper intertidal locations. SSO residues commonly occurred in a discontinuous approximately 3 cm thick band 5-10 cm below the boulder/cobble or pebble/gravel veneer. The SO and SSO occurrences in the 2002 survey closely match the locations where they were found in 1992 and earlier surveys; however, in 2002 residual SSO patches are more discontinuous and thinner than they were in the earlier surveys. These sites are biased toward SSO persistence; those that have SSO residues represent less than 0.5% of the originally oiled shorelines in PWS. Despite evidence of continued oil weathering, both at the surface and in the sub-surface, it is clear that the natural cleaning processes at these particular locations are slow. The slow weathering rates are a consequence of the oil residue being incorporated in finer sediments (fine sand, silt, mix) and isolated from active weathering processes as boulders and outcrops, shallow bedrock asperities, or boulder-armoring create wave shadows and limit effective physical action on shorelines.  相似文献   

基于DSAS和FA的1959—2002年黄河三角洲海岸线演变规律及影响因素研究   总被引：4，自引：1，他引：4  

刘鹏  王庆  战超  王昕  杜国云  李雪艳 《海洋与湖沼》2015,46(3):585-594

采用数字岸线分析系统(DSAS)和岸线分形分析(FA),以不同年份测量的9期历史地图为数据源,对1959—2002年黄河三角洲海岸线长度、形态及变化过程进行了定量分析。结果表明,从1959—1984年黄河三角洲海岸线长度减小,岸线平面轮廓形态变得平滑、简单;从1984—2002年三角洲海岸线长度增加,岸线平面轮廓形态变得曲折、复杂。与此同时,整个三角洲海岸中前进、后退及进退平衡岸线的比例构成变化也具有显著的阶段性。从总体上看,前进岸线所占比例变化呈不断减小趋势,但1980—1984年、1996—2000年曾有两次短暂的突然增大。从岸线变化速率及其空间分布看,三角洲海岸线进退变化于1968—1974年、1992—1996年两度达到或接近平衡状态。根据初步分析,1959—2002年黄河三角洲岸线演变是在黄河入海泥沙总体减少的背景下发生的,受到河口地貌变迁、海岸沉积动力系统的深刻影响。  相似文献   

Mapping bathymetry based on waterlines observed from low altitude Helikite remote sensing platform     

JO Young-Heon  SHA Jin  KWON Jae-Il  JUN Kicheon  PARK Jinku 《海洋学报(英文版)》2015,34(9):110-116

Mapping shoreline changes along coastal regions is critically important in monitoring continuously rising sea surface heights due to climate change and frequent severe storms. Thus, it is especially important if the region has very high tidal ranges over very gentle tidal flats, which is a very vulnerable region. Although the various remote sensing platforms can be used to map shoreline changes, the spatial and temporal resolutions are not enough to obtain it for a short time. Accordingly, in this study we introduce the newly developed low altitude Helikite remote sensing platform to achieve much better resolutions of shorelines and a bathymetry. The Helikite stands for Helium balloon and Kite, which is a kind of aerial platform that uses the advantages of both a Helium balloon and a kite. Field experiments were conducted in the Jaebu Island, off the coast of the west Korean Peninsula in January 29, 2011. In order to extract shorelines from the consecutive images taken by the low altitude Helikite remote sensing platform, active contours without edges (ACWE) is used. Edges or boundaries exist primarily on places between one type of objective and the other. Since the hydrodynamic pressure has an effect everywhere, the locations of the waterlines can be the isobath lines. We could map several waterlines, which would enable us to complete a local bathymetry map ranges from 35 to 60 cm depth. The error resulting from applying ACWE algorithm to the imagery to determine the waterline is approximately less than 1 m. Therefore, it is very unique way to obtain such high resolutions of bathymetry with high accuracy for the regions of extremely high tidal ranges for a short time.  相似文献   

近60年莱州湾东部砂质海岸地貌的时空动态     

战超  于君宝  王庆  栗云召  周迪 《海洋学报》2017,39(9):90-100

在野外考察的基础上,以不同时期测量和成像的海图、地形图和高分辨率遥感影像为数据源,综合使用数字岸线分析、遥感、地理信息系统等方法,对近60年来莱州湾东部砂质海岸（界河口-刁龙嘴）地貌演变进行研究。结果表明,研究期内莱州湾东部岸线迁移和水下岸坡冲淤存在强烈的时空差异。岸线迁移表现为冲淤进退交替发生,其在时间过程上具有非线性的显著特点。1959-2013年,侵蚀岸线所占比例波动起伏,具有阶段性。侵蚀岸段年均演变速率以1985年为界分成两个阶段,前期由极大值4.95 m/a（1959-1969年）锐减至极小值1.97 m/a（1969-1985年）,后期由1.97 m/a增大到4.43 m/a（1985-1998年）,之后均处于高强度侵蚀。岸线迁移空间分布的差异性主要表现在4个岬湾的岸线变迁特征与莱州湾东岸岸线整体变迁并不一致。同时,水下岸坡冲淤条带大体相间分布,同一岸段1959-1985年和1985-2008年的冲淤演变趋势基本相反。进一步分析表明最近60年来,莱州湾东部砂岸在水库拦沙、潮上带工厂化水产养殖、大型海岸工程等人类活动的地貌效应共同控制下,发生了5次岸线淤积前进与侵蚀后退以及冲淤速率大小的交替。  相似文献   

Variations in the response of the dune coast of northern France to major storms as a function of available beach sediment volume          下载免费PDF全文

Adrien Crapoulet  Arnaud Héquette  Denis Marin  Franck Levoy  Patrice Bretel 《地球表面变化过程与地形》2017,42(11):1603-1622

A series of airborne topographic LiDAR data were obtained from May 2008 to January 2014 over two coastal sites of northern France (Bay of Wissant and east of Dunkirk). These data were used with wind and tide gauge measurements to assess the impacts of storms on beaches and coastal dunes, and particularly of the series of major storms that hit western Europe during the fall and early winter of 2013. Our results show a high variability in shoreline response from one site to the other, but also within each coastal site. Coastal dune erosion and shoreline retreat occurred at both sites, particularly on the coast of the Bay of Wissant where shoreline retreat up to about 40 m was measured. However, stability or even shoreline advance were also observed despite the occurrence of an extreme water level with a return period >100 years during the storm Xaver in early December 2013. Comparison of shoreline change with variations of coastal dune and upper beach volumes revealed only weak relationships. Our results nevertheless showed that shoreline behavior seems to strongly depend on the initial sediment volume on the upper beach before the occurrence of the storms. According to our measurements, an upper beach volume of about 30 m³ m^?1 between the dune toe and the mean high water level is sufficient at these sites to protect the coastal dunes from storm waves associated with high water levels with return periods >10 years. The identification of such thresholds in terms of upper beach width or sediment volume may represent valuable information for improving the management of shoreline change by providing an estimate of the minimum quantity of sand on the upper beach necessary to ensure shoreline stability in this region. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Drivers of island beach evolution: insights from an island-scale study at Boa Vista (Cabo Verde)     

Cesária Gomes  Ana Nobre Silva  Rui Taborda  Filipe Santos  Luís Rebelo  Aníbal Medina 《地球表面变化过程与地形》2019,44(14):2810-2822

Beach erosion poses significant threat to small island economies which are generally highly dependent on coastal tourism. This work investigates the evolution of the low-lying sandy coast of Boa Vista through an integrated characterization of coastline and shoreline indicators (over the past four decades) based on aerial imagery. It was found that tandem use of the two indicators was important to obtain a reliable perspective of the Boa Vista low-lying coastal evolution across a wide range of coastal environments. Results indicate that between 1968 and 2010 the coast was relatively stable, although some spatial variability was recognized. The largest changes were observed at the tips of embayed beaches and a clear coastal progradation was found at the southern (downwind) coastal sectors. Coastal evolution has been dominated by sediment budget and the results put in evidence the sedimentary connections between the beaches across the island, either through bypass and overpass processes. Findings show that understanding coastal evolution at low-lying islands should be supported on island-scale observations, being the only scale capable to capture the sedimentary connections between beach systems, that often control coastal evolution. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.  相似文献   

基于数字岸线分析系统的海岸线时空变化速率分析——以海州湾为例   总被引：2，自引：1，他引：1  

沈昆明  李安龙  蒋玉波  刘鑫仓 《海洋学报》2020,42(5):117-127

本文选取1985?2018年间具有代表性的6期Landsat遥感影像,运用数字海岸线分析系统,综合利用面积法和基线法定量分析海州湾的岸线变迁,并进行岸线分类和驱动力分析。结果表明,30多年来海州湾岸线整体呈持续向海推进的态势,增长岸线比例总体处于不断增加的趋势,除了2005?2009年发生短暂的减小;1985?2018年,岸线长度增加了10.40 km,陆域面积增加了52.84 km2;海州湾岸线以人工岸线为主,且比重日渐增大,从1985年的47.90%到2018年的70.88%,前中期的沿海围垦养殖及后期的围海造陆是海岸线变迁的主要驱动力;其终点变化速率为26.09 m/a,净海岸线变化为155.12 m,记录增加总横断面在各个时期均大于50%,岸线变迁最剧烈的区域为新沭河?高公岛段,陆域增长点在于赣榆新城、连云新城建设和连云港港口建设。  相似文献