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1.
Shoreline changes along the south Gujarat coast has been analyzed by using USGS Digital Shoreline Analysis System (DSAS) version 4.3. Multi-temporal satellite images pertaining to 1972, 1990, 2001 and 2011 were used to extract the shoreline. The High water line (HTL) is considered as shoreline and visual interpretation of satellite imageries has been carried out to demarcate the HTL based on various geomorphology and land use & land cover features. The present study used the Linear Regression Method (LRR) to calculate shoreline change rate. Based on the rate of shoreline changes, the coastal stretches of study area has been classified in to high erosion, low erosion, stable, low accretion and high accretion coast. The study found that about 69.31 % of the South Gujarat coast is eroding, about 18.40 % of coast is stable and remaining 12.28 % of the coast is accreting in nature. Field investigation was carried out which confirmed the coastal erosion/accretion derived from the analysis. The high erosion area are mostly found along the Umergaon (near Fansa, Maroli, Nargol, Varili river mouth, Umergaon light house) and Pardi (Kolak, Udwara)Taluka in Valsad district. Stable coastal length of the study area is 21.59 km and mostly found in Nani Dandi and near Onjal. High accretion (3.70 %) was only found near Hajira and low accretion (8.58 %) are distributed the study area. The main causes of coastal erosion of the study area were the strong tidal currents accompanied by wave action and reduced the sediment load of the river.  相似文献   

2.
The shoreline is one of the rapidly changing landforms in coastal areas.They are the key element in coastal GIS and provide the most information on coastal land form dynamics.Therefore,accurate detection and frequent monitoring of shorelines is very essential to understand the coastal processes and dynamics of various coastal features.The present study is to investigate the shoreline changes along the coast between Kanyakumari and Tuticorin of south India(where hydrodynamic and morphologic changes occur continuously after the December 2004 tsunami)by using Digital Shoreline Analysis System(DSAS),an extension of ArcGIS.Multidate IRS and Landsat Satellite data(1999,2001,2003,2005,2007,and 2009)are used to extract the shorelines.The data is processed by using the ERDAS IMAGINE 9.1 software and analyzed by ArcGIS 9.2 workstation.The rates of shoreline changes are estimated by three statistical methods,namely,End Point Rate(EPR),Linear Regression Rate(LRR),and Least Me-dian of Squares(LMS)by using DSAS.The study reveals that most of the study area has undergoing erosion.Both natural and an-thropogenic processes along the coast modify the shoreline configuration and control the erosion and accretion of the coastal zones.The coastal zones along the estuary have experienced accretion due to the littoral processes.The zones with headlands have more eroded than other zones along the study area.The study also shows that the coastal zones where sand is mined have relatively more rate of erosion than that of the other zones.Improper and unsustainable sand mining may also lead to severe erosion problem along this area.The shoreline change rates are altered by various geological processes along the coast.Thus,the present study implies that proper beach filling and nourishment projects should be made in the study area to save from hazards.It also indicates the advantage and suitability of DSAS to assess the shoreline changes compared with the traditional manual shoreline change analysis and prom-ising its applications for coastal zone management in other regions.  相似文献   

3.
Shoreline is the dynamic interfaces of both terrestrial and marine environment, which constantly affected by natural coastal processes includes wave, tide, littoral drift and cyclonic storms as well as coastal development. Wave induced littoral drift and fluvial discharge causing the gradual inlet migration and has the concurrent impact on shoreline of Chilika lagoon. This study is to determine the long-term shoreline changes along the coast of Chilika lagoon. Historical satellite images were used to analyse the shoreline erosion and accretion based on statistical approach. The satellite data from 1975 to 2015 were processed by using ERDAS Imagine and the shorelines are extracted. The shoreline oscillation was analysed at an interval of 100 m along the coast of Chilika lagoon using DSAS software. Most commonly used statistical methods such as end point rate and linear regression rate are used. The shoreline change analysis for entire coast of the lagoon since 40 years (1975–2015) indicates that 62% is of accretion, 25% is under stable coast and erosion is 13%. The result reveals that the lagoon coast shows high accretion of 9.12 m/year at updrift side of the lagoon inlet whereas the downdrift side shows high erosion of ??10.73 m/year due to the wave induced northeasterly longshore sediment transport round the year and riverine discharge. This study would provide the potential erosion and accretion area at Chilika lagoon coast and would help in adaptive shoreline management plan.  相似文献   

4.
Sandy beaches of the eastern coast zone in Eastern Laizhou Bay represent the most popular tourist, recreational destinations and constitute some of the most valuable restates in China. This paper presents the detection of shoreline changes in Laizhou Bay East Bank using an automatic histogram thresholding algorithm on the basis of multi-temporal Landsat images. Shoreline change rates (SCR) and shoreline change areas (SCA) were retrieved using the statistical approach and zonal change detection method, respectively. Results showed that during 1979–2010 a large portion (over 59.8 %) of shoreline are dominated by a retreating process with an average rate of ?2.01 m/year, while other parts of shoreline exhibited a seaward advancing trend due to intense land reclamation activities. It is our anticipation that the result of this work would support sandy beaches protection and management in China coast.  相似文献   

5.
National policies and legal decisions are very much dependent on the position of the shoreline. Shoreline change rates are frequently employed to summarize historical shoreline movements. This also helps to predict the future position of the shoreline based on the perceived historical trends. In this regard, the future shoreline positions at both the long-term, that is 2050, and short-term, that is 2015, time interval was predicted using the End Point Rate (EPR) model along the Junput Coast of West Bengal, India. The whole project work was divided into five parts. The first part showed the detection of shoreline from satellite data like IRS LISS Ⅳ and Landsat 7 ETM+ and from the Survey of India Toposheet. The second part gave the glimpse of the dynamic segmentation of the shoreline to get the dynamically segmented nodal points along the shoreline. Shoreline prediction for the years 2015 and 2050 using End Point Rate (EPR) model was done in the third part. In the fourth part, Coastal Terrain Model (CTM) was prepared, and the digital shoreline estimated. The model result was validated and accuracy assessed with respect to the GPS data collected from the field at the fifth stage. Finally at the end of the present work, limitations of the project and the future scope of the work was sited.  相似文献   

6.
TOPSAR wave spectra model and coastal erosion detection   总被引：2，自引：0，他引：2  
This paper presents work done utilizing TOPSAR data to detect shoreline change along the Terengganu coast (Malaysia). TOPSAR data were used to extract information on wave spectra. This wave spectra information was then used to model shoreline changes by investigating the wave refraction patterns. From these patterns, the volume transport at several locations was estimated. The shoreline change model developed was designed to cover a 20 km stretch of shoreline of Kuala Terengganu. The model utilized data from aerial photographs, TOPSAR data and ground truth data. The location of sedimentation and erosion along the shoreline of Kuala Terengganu was estimated. The wave spectra extracted from TOPSAR data showed wavelengths ranging from 20 m to 175 m. The main direction of the waves given by the spectra was from the northeast. The wave refraction patterns varied, showing both convergence and divergence, indicating erosion and sedimentation locations, respectively. A comparison between the TOPSAR shoreline change model and aerial photographs and ground truth data showed a significant relationship. Finally, the regression model showed that erosion occurred particularly at Sultan Mahmed Airport, at a rate of −1.5 m/year. The maximum rate of sedimentation along the 20 km stretch was 1 m/year.  相似文献   

7.
Beach heights and tidal variation have large impacts on the accuracy of estimates of coastline position and its historical changes of a wider and flatter beach based on remote sensing data. This study presents an approach to analysis of waterline movement based on the beach slope, estimated from two effective images with Landsat images data. Two images acquired at different stages of the tide were processed to delineate accurately the position of the waterline. Then waterlines were assigned heights using elevations predicted by a two-dimensional non-linear tidal assimilation model. Beach slope can be calculated piecewise using the heighted shorelines based on the equiangular triangle theory. The positions of the national tidal height datum coastline can be obtained by the beach slope calculation method to accurately monitor the changing of coastline. A change in the coastline of the southwest tidal flat of the Yellow River delta, from Tianshuigou to the Xiaoqing River mouth, was detected by combining field measurements of profiles and bathymetric data. The root mean squared error (RMSE) of the calculated slope of the intertidal zone was one order of magnitude less than the measured slope. The minimum error of self-consistency check is 0.2%. The RMSE between the coastlines estimated by the proposed method and those surveyed data varies from 53.98 m to 217.72 m. It is shown that this method is more suitable for the two years and over the time scales of shoreline change monitoring. To assess erosion/accretion patterns in the tidal flat, and the controlling factors, the volume of the beach was investigated as a possible indicator. The accepted coastline position and changes in the beach volume were used to monitor the changing pattern of accretion and erosion along the coast southwest of the recent Yellow River mouth.  相似文献   

8.
Digha coastal region in the northeastern part of the Bay of Bengal is potentially vulnerable to erosional hazard. The present study assessed the coastal erosion vulnerability along this 65 km long coastal stretch located between Rasulpur (Midnapur) and Subarnarekha (Balasore) estuarine complex, which had been subjected to anthropogenic intervention. Multi-resolution Landsat satellite imagery were used for shoreline change study from 1972 to 2010. During this period, accretion was recorded updrift of artificial structures, viz, seawall, groin, pylons and jetties; while, extensive erosion was recorded in downdrift areas of these structures. Assessment was subsequently divided into four categories ranging from “high erosion” to “accretion”. Data from several sources were compiled to map landuse and human activities in the coastal zone. This map was divided into four categories, ranging from “very high capital” to “no capital” landuse. Population density map of the surrounding coastal villages was generated using census data, and divided into four categories ranging from “high density area” to “very low density area”. Subsequently, coastal erosion vulnerability was assessed by combining coastal retreat with landuse type and population density in this study area using simple vector algebraic technique. Zones of vulnerability of different magnitude (viz., very high, high, moderate, and low) have been identified. Furthermore, calculation of “imminent collapse zone (ICZ)” shows that maximum values are around artificial structures and anthropogenic activities. The coastal erosion vulnerability map prepared from this study can be used for proper planning and management of this coastal region.  相似文献   

9.
Coastal zone is highly volatile ecosystem which is always in adjustments. Loss of shore line will cause severe impact on human life and as well as their properties. Remote sensing is a reliable technique to study the historical shoreline changes. Therefore in this paper long term shoreline oscillations of Cauvery delta shorelines at Poompuhar, Tharangambadi and Nagapattinam were studied using satellite imageries and the same was physically observed at the above three locations with the help of reference pillars and compared mutually. It was observed that the shoreline at Poompuhar is under accretion at the rate of 1.79m/ year and other shoreline stretches at Tharangambadi and Nagapattinam were under erosion at 0.4888m/ year and 0.4985m/ year respectively. It was also observed that the remote sensing study qualitatively matches with the physical observation for all the three coastal stretches of the study area.  相似文献   

10.
The impact of wave spectra modulation transfer function (MTF) in shoreline change model accuracy has been presented. The MTF consisted of real aperture radar (RAR) and velocity-bunching which is utilized to map the wave spectra observed from ERS-1 into the observed real ocean wave spectra. Based on this information, the shoreline change model have developed. Two hypotheses were concerned with the shoreline change model based on ERS-1 wave spectra. First, there is a significant difference between RAR and velocity-bunching modulations for ERS-1 wave spectra modeling. Second, this significant difference is induced a different spatial variation for shoreline change pattern.This study shows that there was the significant difference between velocity-bunching and quasi-linear models. The study shows that velocity-bunching model produces wave spectra pattern approximately close to the real ocean wave compared to the quasi-linear model. The error percentage occurred with velocity-bunching and quasi-linear models were 33.5 and 46.7%, respectively. The highest rate of erosion occurred to the shore south of Chendering with −5 m per year and the highest rate of sedimentation occurred to north of Chendering headland with 3 m per year. It can be concluded that ERS-1 data could be used to model shoreline change and identify the locations of erosion and sedimentation. The sedimentation was occurred due to the effect of lowest wave spectra energy captured along the range direction while the erosion was occurred due to highest spectra energy captured near azimuth direction.  相似文献   

11.
Funafuti Atoll, Tuvalu is located in the southwestern Pacific Ocean, which has experienced some of the highest rates of global sea-level rise over the past 60 years. Atoll islands are low-lying accumulations of reef-derived sediment that provide the only habitable land in Tuvalu, and are considered vulnerable to the myriad possible impacts of climate change, especially sea-level rise. This study examines the shoreline change of twenty-eight islands in Funafuti Atoll between 2005 and 2015 using 0.65 m QuickBird, 0.46 m WorldView-2, and 0.31 m WorldView-3 imagery using an image segmentation and decision tree classification. Shoreline change estimates are compared to previous study that used a visual interpretation approach. The feasibility of estimating island area with Landsat-8 Operational Land Imager (OLI) data is explored using CLASlite software. Results indicate a 0.13% (0.35 ha) decrease in net island area over the study time period, with 13 islands decreasing in area and 15 islands increasing in area. Substantial decreases in island area occurred on the islands of Fuagea, Tefala and Vasafua, which coincides with the timing of Cyclone Pam in March, 2015. Comparison between the WorldView-2 shoreline maps and those created from Landstat-8 indicate that the estimates tend to be in higher agreement for islands that have an area > 0.5 ha, a compact shape, and no built structures. Ten islands had > 90% agreement, with percent disagreements ranging from 2.78 to 100%. The methods and results of this study speak to the potential of automated EoV shoreline monitoring through segmentation and classification tree approach, which would reduce down data processing and analysis time. With the growing constellation of high and medium spatial resolution satellite-based sensors and the development of semi or fully automated image processing technology, it is now possible to remotely assess the short and medium-term shoreline dynamics on dynamic atolls. Landsat estimates were reasonably matched to those derived from fine resolution imagery, with some caveats about island size and shape.  相似文献   

12.
Changes in shoreline, coral reef and seafloor have been mapped using remote sensing satellite data of IRS LISS-III (1998), IRS LISS-II (1988), Survey of India Topographic sheet (1969), Naval Hydrographic Chart (NHO) 1975 and bathymetry data (1999) with ARC-INFO and ARC-VIEW GIS. The analysis of multi-date shoreline maps showed that 4.34 and 23.49 km2 of the mainland coast and 4.14 and 3.31 km2 areas of island coast have been eroded and accreted, respectively, in the Gulf of Mannar. The analysis of multi-date coral reef maps showed that 25.52 km2 of reef area and 2.16 km2 of reef vegetation in Gulf of Mannar have been lost over a period of ten years. The analysis of multi-date bathymetry data indicates that the depth of seafloor has decreased along the coast and around the islands in the study area. The average reduction of depth in seafloor has been estimated as 0.51m over a period of twenty four years. The increased suspended sediment concentration due to coastal and island erosion, and raised reef due to emerging of coast by tectonic movement are responsible for coral reef degradation in the Gulf of Mannar. Validation by ground truth has confirmed these results.  相似文献   

13.
Abstract

Shoreline extraction is fundamental and inevitable for several studies. Ascertaining the precise spatial location of the shoreline is crucial. Recently, the need for using remote sensing data to accomplish the complex task of automatic extraction of features, such as shoreline, has considerably increased. Automated feature extraction can drastically minimize the time and cost of data acquisition and database updating. Effective and fast approaches are essential to monitor coastline retreat and update shoreline maps. Here, we present a flexible mathematical morphology-driven approach for shoreline extraction algorithm from satellite imageries. The salient features of this work are the preservation of actual size and shape of the shorelines, run-time structuring element definition, semi-automation, faster processing, and single band adaptability. The proposed approach is tested with various sensor-driven images with low to high resolutions. Accuracy of the developed methodology has been assessed with manually prepared ground truths of the study area and compared with an existing shoreline classification approach. The proposed approach is found successful in shoreline extraction from the wide variety of satellite images based on the results drawn from visual and quantitative assessments.  相似文献   

14.
江苏省海岸线演变及地质灾害遥感分析   总被引：3，自引：0，他引：3  
江苏省漫长的海岸曾经历了大淤大蚀的沧桑变化。现代海岸仍经常受到侵蚀崩岸、岸滩淤涨以及沿岸泥沙流的袭扰破坏。沿岸港口建设、交通航运及滩涂围垦等也不时受到危害,成为江苏海岸带特有的地质灾害。  相似文献   

15.
遥感和GIS支持下的九段沙岸线提取及变迁研究   总被引：2，自引：0，他引：2  
在遥感和GIS的支持下,利用集成了非监督分类、地图综合、离散地物去除和岸线追踪等技术的shoreline-Extractor软件,解译上海市九段沙自然保护区2001年、2005年和2008年的岸线信息;对解译的目标岸线分别进行空间分辨率为30 m,90 m,150 m,210 m和270 m的重采样,计算其分维数,并进行岸线长度、沙洲面积和分形特征的分析,进而对九段沙岸线变迁的重点区域进行了分析。研究表明,随时间推移,九段沙的上沙、中沙和下沙3个沙洲淤长的部位并不一致,其中上沙北部区域、中沙东北和西南区域、下沙东北和西南区域淤长较为明显;岸线长度与沙洲面积的变化区域几乎一致,即上沙增长较快、下沙次之、中沙缓慢;九段沙岸线具有显著的分形性质,整体分维数呈增加态势,其中上沙和中沙的分维数小于整体分维数,而下沙的分维数大于整体分维数。  相似文献   

16.
Coastal zone is very dynamic, being the meeting place of land and sea water. The development in coastal area and subsequent population growth have given rise to problems such as erosion, sedimentation, saltwater intrusion, degradation of natural resources, etc. Satellite data has proved to be more appropriate for change detections quantifying and monitoring coastal zones compared to conventional sources. An attempt is being made to elucidate the effect of shoreline changes with reference to the spatial and field data observed along the Tharangampadi area. The base map was prepared on 1:50,000 scale for delineation and identification of shoreline changes. The spatial variability of shoreline changes are studied using IRS 1B LISS-II 1991, IRS 1C LISS-III 2004 and IRS P6 LISS-IV and IRS 1D PAN merge data 2006. The corresponding Survey of India toposheets of 1852, 1972 and survey and land record village map of 1918 also supplemented for this study. The kind and extent of shoreline changes were investigated by using GPS during ground truth verification. The results are analyzed and presented in this paper. The study results revealed that 180 m receding of the shoreline occurred in the past 155 years.  相似文献   

17.
The city of Mangalore is situated at the confluence of rivers Gurpur and Netravati. Two spits are formed in this area, i.e., northern spit of “Bengre” and the southern spit of “Ullal” as the rivers flow close and parallel to the seashore for some distance. The spits have been subjected to constant geomorphological changes in length, width, position, accretion and erosion patterns etc., for the past several decades. A seawall was constructed in 1984 around the tip of Bengre spit and another one along the shoreline of Ullal spit in 1987, by the Government of Karnataka in order to prevent the spits from being eroded. Two breakwaters were also constructed in 1992 near the estuarine mouth as part of the development of old Mangalore Port. The paper presents the results of a study undertaken to identify the geomorphologic changes that occurred in the area, using 1RS-1A/1C data for the years of 1988, 1994. 1996. The study clearly demonstrated that the 1RS data could be effectively utilized for monitoring the geodynamics of an area. It was observed that the spits were highly unstable earlier. However, the construction of seawalls was helpful in arresting the migration of the estuarine mouth and in stabilizing the spits against coastal erosion.  相似文献   

18.
2004年印度洋海啸印尼亚齐省灾情遥感监测与分析   总被引：4，自引：1，他引：4  
2004年12月底印尼苏门答腊岛西北海岸发生里氏9.0级地震,引发印度洋沿岸的印尼、斯里兰卡、泰国、印度等国家先后遭受强烈海啸。印度尼西亚亚齐省是遭受海啸灾害最严重的地区之一。为了评估海啸灾害造成的严重影响,应用遥感和地理信息系统技术,以2005-01-07英国DMC小卫星遥感影像为基础数据源,结合收集到的该地区灾前(2001年)LandsatETM 遥感影像,对亚齐省进行了监测和快速评估。监测结果表明距离震中位置较近的亚齐省苏门答腊岛西海岸遭受影响较严重,亚齐省苏门答腊岛西海岸由于距离震中位置较近遭受严重影响,而苏门答腊岛东海岸则影响较轻,受灾最严重的地区是亚齐省首府班达亚齐市附近。经统计,整个亚齐省遭受海啸严重影响的地区面积约为483km2,其中城市建成区受淹面积约为26·2km2,乡村(镇)地区受淹面积约为430·5km2。文章的最后还结合数字高程模型对海啸灾情的结果进行了分析。结果表明,绝大多数因海啸而受淹地区高程低于20m。  相似文献   

19.
利用 LiDAR 点云提取有地形约束的光滑海岸线   总被引：1，自引：0，他引：1  
针对传统海岸线提取算法误差大、在地形突变区域形变大的缺点,提出了一种基于离散 LiDAR 点云提取有地形约束海岸线的方法.首先,通过离散点云构建约束三角网,减少内插规则格网的误差并且保证海岸线不穿越地形结构;其次,进行顾及地形结构的点云高程修正,在数据源上缓解海岸线的平滑问题;最后采取二次多项式法消除毛刺,利用动态阈值张力样条函数内插生成光滑海岸线.  相似文献   

20.
This paper deals with the processes operating on the beaches of Goa, interpreted from imagery, followed by ground-truth collection and field checks. Studies on Landsat imagery bring out two distinct coastal geomorphological features, one north and the other south of Vasco-da-Gama. The beaches to the south indicate the prograding shoreline with deposition being the dominant phenomenon. The beaches to the north of Vasco-da-Gama reveal a retrograding shoreline where erosion is dominant. The presence of chimneys and stacks to the north of Vasco-da-Gama are characteristic of intensive erosional action while to the south a wide regular beach backed by a palaeo-strand line points to deposition. The pattern of the sediment load (in Band 4) is used as an index of longshore current movement. The action of erosion as against that of deposition in the two regions can be surmised from the diffused pattern vis-a-vis the uniformly wide even tone. Sand samples from the northern portion give a sorting coefficient of 1.100 while the southern portion shows a value of 0.712. It is hypothesised that the promontory on which Vasco-da-Gama lies is responsible for the formation of two different geomorphic zones.  相似文献   

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