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Short-Term Morphological and ShorelineChanges at Trinkat Island, Andaman andNicobar, India, After the 2004 TsunamiP. Yunus Alia & A. C. Narayanab

a Department of Natural Environmental Studies, Graduate School ofFrontier Science, The University of Tokyo, Kashiwa, Japanb Centre for Earth & Space Sciences, University of Hyderabad,Hyderabad, IndiaAccepted author version posted online: 23 Apr 2014.Publishedonline: 10 Jul 2014.

To cite this article: P. Yunus Ali & A. C. Narayana (2015) Short-Term Morphological and ShorelineChanges at Trinkat Island, Andaman and Nicobar, India, After the 2004 Tsunami, Marine Geodesy, 38:1,26-39, DOI: 10.1080/01490419.2014.908795

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Marine Geodesy, 38:26–39, 2015Copyright © Taylor & Francis Group, LLCISSN: 0149-0419 print / 1521-060X onlineDOI: 10.1080/01490419.2014.908795

Short-Term Morphological and Shoreline Changesat Trinkat Island, Andaman and Nicobar, India,

After the 2004 Tsunami

P. YUNUS ALI1 AND A. C. NARAYANA2

1Department of Natural Environmental Studies, Graduate School of FrontierScience, The University of Tokyo, Kashiwa, Japan2Centre for Earth & Space Sciences, University of Hyderabad, Hyderabad, India

The tsunami waves generated during the Sumatra-Andaman earthquake of 26 December2004 devastated the coastal area along Trinkat Island, causing sudden changes to themorphology of the landforms. This study uses a series of satellite images to record theshort-term morphological response and shoreline changes as well as the recovery ofcoastal land after its destruction. Results indicate that the island experienced substantialerosion and a significant reduction in land area. Shoreline erosion is more prevalentthan accretion at an average linear regression rate of ∼−9 m per year between 2004and 2013. The major morphological changes at Trinkat Island were observed in coastalinlets, beaches, and bay head-lands. Straight beaches had almost recovered eight yearsafter the tsunami; however, erosion is continually observed in other areas. Our studywill help understanding the response and recovery of shorelines in Indian Ocean regionsafter the 2004 tsunami.

Keywords December 26, 2004 tsunami, coastal landforms, shoreline erosion, beachrecovery, Andaman and Nicobar, Trinkat Island

1. Introduction

The devastating tsunami of 2004 not only caused major casualties and damage in IndianOcean countries (e.g., India, Indonesia, Sri Lanka, and Thailand) but also caused significantchanges to the morphology of coasts in these countries (Kench et al. 2006; Choowong et al.2009; Paris et al. 2009; Meilianda et al. 2010). Land uplift, subsidence, removal of sandybeaches, coral destruction, sediment scouring, sediment transport and deposition, sedimentre-distribution and destruction of sand dunes and wetlands were reported after the tsunami(e.g., Bilham 2005; Meltzner et al. 2006; Narayana et al. 2007; Umitsu et al. 2007; Narayana2010; Paris et al. 2010). The response and recovery of coastal morphological features afterthe 2004 tsunami were studied by various researchers (e.g., Wong 2009; Liew et al. 2010;Meilianda et al. 2010). The recovery of the shoreline and morphological features variedacross coastal regions, depending on the geological and climatic conditions. In some areas,

Received 14 September 2013; accepted 24 March 2014.Address correspondence to A. C. Narayana, Centre for Earth & Space Sciences, University of

Hyderabad, Hyderabad, 500-046, India. E-mail: acnes@uohyd.ernet.inColor versions of one or more of the figures in the article can be found online at

www.tandfonline.com/umgd.

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Morphological and Shoreline Changes at Trinkat Island 27

the coastal land recovered at a very fast rate. For example, the recovery of Aceh coast,Sumatra, to its original layout has been remarkably swift (Liew et al. 2010). Along thePhang-nga coast, Thailand, the entire stretch of beach completely recovered within twoyears (Choowong et al. 2009). Currently, an understanding of the geomorphic processesthat underlie coastal evolution and shoreline changes along the Andaman and Nicobar coastis lacking.

Generally, two approaches are used for shoreline and coastal land change analysis: field-based methods, including topographic survey techniques (Dolan et al. 1979; Thom and Hall1991; Ruggiero et al. 2005) and remote sensing interpretations using aerial photographsand time series satellite images (Dolan et al. 1991; Fletcher et al. 2003; Ford 2013). Thefirst technique provides accurate and detailed information, but it is time consuming andcostly. With the advent of modern technology and the development of high-resolutionsensors, remote sensing-based approaches for mapping coastal and shoreline changes iswidely used (Dolan et al. 1991; Zhang et al. 2005; Ford 2011, 2013). The remote sensing-based surveys are more cost effective and require less time for processing as compared tofield based methods. For example, images that depicted the 2004 tsunami damage werepublished only a few days afterwards (e.g., CRISP 2004; NASA 2007). Once satelliteimages are procured and processed, the shorelines are interpreted using the vegetationboundaries (Webb and Kench 2010) or the toe of the beach. Today, powerful GIS packagesare available to perform the vectorization of shorelines either by onscreen digitization orby automatic extraction.

In this paper, we demonstrate the response and recovery of Trinkat Island, Andamanand Nicobar Islands, India, which was affected by the 2004 tsunami. Shoreline and mor-phological changes for six time periods (i.e., the changes during each year from 2004 to2008 and during a five-year period from 2008 to 2013) are analyzed and presented.

2. 26 December 2004 Tsunami and Andaman Islands

On Sunday, 26 December 2004, at 00:58:53 UTC (06:28 AM local time), a 9.3 magni-tude earthquake occurred beneath the Indian Ocean at a depth of 30 km. The earthquakeoriginated at 3.3◦N, 96.0◦E near the west coast of the Indonesian island of Sumatra andsubsequently generated a series of tsunami waves. The Sumatra-Andaman earthquake wasthe largest seismic event to affect coastal countries in the Indian Ocean in more than40 years (Lay et al. 2005). The Andaman and Nicobar islands, which are located near thesoutheastern coast of India, are the closest land masses to the epicenter of the earthquake;thus the tsunami was highly devastating in the area. Destructive waves reached the coastsof the Andaman and Nicobar islands 2-4 hours after the earthquake. Trinkat Island in Nan-cowry Tahsil, which is located between 8◦02′10′′–8◦07′10′′N and 93◦33′40′′–93◦36′15′′E(Figure 1), is one of the Nicobar islands that is situated southeast of the Bay of Bengal.Large-scale destruction occurred at Trinkat Island during the tsunami (Narayana 2011).The total population of Trinkat Island is 432 (64 households) (NIC 2011).

3. Materials and Methods

3.1. Satellite Images

Satellite images of the Trinkat Island area at various times during 2004–2013 are usedto analyze short-term morphological responses and shoreline changes after the tsunami

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Figure 1. Map showing the location of Trinkat Island in the Andaman and Nicobar islands of India.The spatial extent of the shoreline position between 2004 and 2013 is marked in the image.

(Figure 2). Images from the Indian remote sensing satellite IRS-P6 LISS III with a spatialresolution of 23.5 m were acquired for 27 February 2004, 4 January 2005, 29 April 2006,and 13 January 2008. IRS 1D images with a spatial resolution of 30 m were acquiredfor 26 February 2007. Finally, Landsat-8 images with a spatial resolution of 30 m wereacquired for 18 May 2013. All of these images were employed to analyze the erosion rate,net change in shoreline position, and coastal area. Data were preprocessed, but geo-locationerrors might have been introduced because the images were obtained from different sourcesand not necessarily georectified with the same level of accuracy. To address this problem,all of the images were re-projected and geometrically corrected with a 2004 image as areference by using image-to-image registration with a root mean square error (RMSE) of±0.6 pixel. For consistency, we resampled the Landsat and IRS 1D images to a 23.5 mresolution using nearest neighbor interpolation techniques.

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Morphological and Shoreline Changes at Trinkat Island 29

Figure 2. Satellite images of Trinkat Island that were used in this study to digitize the shoreline andcoastal land estimation.

Several methods and techniques were developed to extract the shoreline from theremotely sensed images. In addition to advanced feature extraction algorithms for automaticextraction of the shorelines, the most common techniques for extracting shorelines includedigitizing through visual inspection, band ratios, edge detection, and classification usingsingle or multiple bands (e.g., White and El Asmar 1999; Li et al. 2003; Pardo-Pascualet al. 2012). However, a comparison of these methods is beyond the scope of this work.Here, we employed visual investigation and manual digitization (ArcGIS 10.0) to extractthe shorelines, estimate the erosion-accretion rate and quantify the spatial distribution ofthe coastal area and its changes. Western boundary of the Trinkat Island is characterized byrocky coast; here vegetation was used as a proxy for shoreline interpretation while on theeastern boundary, where sand dominated, toe of the beach was used as the proxy. Whereclouds obscured the data, the areas were masked with the previous year’s shoreline position.The tidal conditions during the image acquisition time significantly affect the accuracy ofthe estimation results. The tidal information during the image acquisition time obtainedfrom Mobile Geographics LLC is summarized in Table 1. Four of the images capture ebbtides, and two of the images capture flood tides.

3.2. Shoreline Analysis

The Digital Shoreline Analysis System (DSAS) (Thieler et al. 2009) is a freely availableapplication that computes statistical changes of multiple shoreline positions. The softwareis run as an add-on tool within ArcGIS. DSAS generates and casts transects perpendicular toa user-specified baseline. Transect intersection positions of the shoreline along the baselineare then recorded. The baseline was established by buffering the pre-tsunami shoreline as thereference shape (following the procedures as required by the DSAS software) (Himmelstoss

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Table 1Areal extent of coastal changes at Trinkat Island during 2004–2013 (i.e., before and after

the tsunami)

Imageacquisition date

Datasource

Tidalinformation (m)

Tidalcondition

Total landarea (km2)

Net change in area(post-tsunami) (km2)

02/27/2004 NRSC 0.55 ebb 16.51 —01/04/2005 NRSC 0.62 ebb 14.20 2.3104/29/2006 NRSC 2.34 flood 12.55 3.9602/26/2007 NRSC 0.90 ebb 12.49 4.0201/13/2008 NRSC 1.87 flood 12.35 4.1605/18/2013 NASA 0.92 ebb 11.87 4.64

2009). Several statistical methods were applied by the DSAS extension: the net shorelinemovement, linear regression rate and end point rate. The net shoreline movement (NSM)reports the distance between the oldest and youngest shoreline positions. This method is anaccustomed measure of the change in shoreline position as it requires only two shorelines.A widely accepted method for computing the long-term rates of shoreline change is thelinear regression rate (LRR) (Crowell and Leatherman, 1999). LRR, which is determinedby fitting least squares regression line, considers all of the data during the calculation. Theend point rate (EPR) is calculated by dividing the distance of the shoreline movement bythe time elapsed between the earliest and latest measurements at each transect. Transectswere cast at a 50 m interval along the baseline (Figure 3). A total of 513 transects weregenerated for the study area.

4. Results and Discussion

4.1. Net Change in Area and Shoreline Movement (2004–2013)

The shoreline movement along the islands can be expressed in terms of the change to thetotal land area (Ford 2013). An estimation of the total land area is a powerful signifier ofisland changes, particularly after a large event. Observations indicate that Trinkat Islandwas significantly affected by the tsunami. A summary of the coastal land area changesfor Trinkat Island is presented in Table 1. Prior to the 2004 tsunami, the areal extent ofTrinkat Island was 16.51 km2, as measured in February 2004 (Figure 2a and Table 1).The area decreased to 14.20 km2 after the disastrous tsunami event, as measured fromimages in January 2005; thus, 2.31 km2 of the land area eroded (Figure 2b and Table 1).The coastal area was further eroded to 12.55 km2 by April 2006. This resulted in a netreduction of 3.96 km2 compared to the pre-tsunami land area in February 2004 (Figure2c and Table 1). Thereafter, the land area gradually decreased to 12.49 km2 by Febru-ary 2007 and to 12.35 km2 by January 2008 (Figures 2d,e and Table 1). Measurementsfrom May 2013 satellite images indicate that the land area further declined to 11.87 km2,which resulted in a net reduction of 4.64 km2 after the tsunami event (Figure 2f andTable 1).

The NSM from the pre-tsunami shoreline to the most recent shoreline for Trinkat Islandwas estimated using DSAS. The positions of the shorelines as measured from a series ofsatellite images during 2004–2013 are shown in Figure 1. The measured NSM over the

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Figure 3. Example of input features and DSAS output as the rate of change of shoreline positions.

2004–2013 periods reveals large-scale shift in the island’s shoreline position (Figure 4a).The average NSM calculated for 513 transects of Trinket Island was ∼−128 m. At somelocations, the calculated NSM indicates that the shoreline has moved ∼−580 m inland.The seaward movement of the shoreline is estimated at a maximum of ∼ +9 m.

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Figure 4. Shoreline rates of change calculated along 513 transects: (a) net shoreline movement(NSM), (b) linear regression rate (LRR), (c) end point rate (EPR) between 2004 and 2005, and (d)the EPR between 2005 and 2013.

4.2. Linear Regression Rate and End Point Rate

The regression results from DSAS for 513 transects are presented in Figure 4b. The LRRanalysis reveals that the Trinkat Island shoreline was retreating at a rate of −9.67 m/yrfollowing the 2004 tsunami event (i.e., 2004–2013). A comparison of the minimum andmaximum values of LRR indicates very high erosion (-49.31 m/yr) and low accretion(+8.30 m/yr) in the region. Only 39 transects (54, 72, 73, 139, 177, 227, 248, 249, 273,

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296, 325, 326, 327 351, 443 to 448, 460 to 475 and 481 to 483) out of 513 exhibit a seawardadvancement of the shoreline after the tsunami. The distribution of the erosion rate forTrinkat Island is irregular as observed from Figure 4b. The erosion is much higher in thecoastal area between transects 390 and 413.

The EPR for Trinkat Island (2004–2005) was found to be an average of −93 m/yr(Figure 4c). At some locations (transects 390-413), the calculated EPR indicates verysevere erosion (up to ∼−530 m/yr). The results of EPR analysis between 2005 and 2013are shown in Figure 4d. The average, minimum and maximum EPR between the post-tsunami measurement and 2013 are −5.59 m/yr, −56.31 m/yr and +29.74 m/yr. Accretionis recorded at many locations. Eighty-five transects out of 513 exhibit accretion, whichindicates that the coastal accretion process is active only in certain locations (Figure 5).The other locations EPR suggest that the shoreline is gradually retreating and as a result,the net coastal land area is decreasing.

4.3. Short-term Morphological Changes

The satellite images depict the presence of a chaotic shoreline along Trinkat Island in theform of severely eroded beaches and eroded coastal land (see Figure 2). Meltzner et al.(2006) in their study recorded land subsidence in the southern and eastern portion of theAndaman and Nicobar Islands after 2004 earthquake with the help of satellite observationbacked by ground truth data. The large scales of the subsidence and erosion are recorded inthe northern and central sections of Trinkat Island (Narayana 2011). We observed changesin the island area and coastal morphology that resulted from tsunami-driven processes andnormal wind-wave dynamics. Major changes were observed in coastal inlets, bays andalong the straight beaches in the east.

4.3.1. Coastal inlets. Along the northern section of the Trinkat coast, where inlets occur,extensive removal of geological materials is observed. The island is separated into twoparts along the existing narrow creek (see Figure 6). The creek/channel widened after thetsunami. Figure 6a depicts Trinket Island and the width of the channel inlet as observedfrom the images that were acquired on February 27, 2004 (pre-tsunami). Figure 6b showsthe enlarged channel, which acted as a catalyst for the separation of the island, as observedfrom the same location on 4 January 2005 (i.e., post-tsunami). Here, the inlet acted as achannel for the tsunami waves to enter inland. The widening of the inlet caused by tsunamiwaves is apparent in the images acquired before and after the tsunami (Figures 6a and6b). The RGB combination of bands post-tsunami in the IRS P6 image acquired in 2005(Figure 6b) depicts vegetation cover in red on the banks of the inlet. Subsequent imagesacquired in 2006 and 2013 record eroded coastal land and stripped vegetation that exposesthe subsurface rocks and unconsolidated material of the coastal plain (Figures 6c–d). Theinternal waves, strong tidal currents and inundation of low-lying areas during the high tidemay have resulted in later severe erosion in this area. The effects of strong internal wavepackets in the sea near Andaman and Nicobar were reported by previous authors (e.g.,Perry and Schimke 1965; Apel et al. 1985). Narayana (2011) attributed the large-scalemorphological changes at Trinkat Island to the coastal configuration and the strong wavereflections during the tsunami.

4.3.2. Straight coast. Straight beaches on the east side of the island were common beforethe tsunami (see Figure 7a). A post-tsunami image reveals an irregular shoreline andseverely eroded sandy beaches (Figure 7b). By 2006, the recovery of the beaches had

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Figure 5. Shoreline erosion and accretion at Trinkat Island as derived from the EPR for 2005–2013.

begun; however, the destroyed beaches were not replaced by new straight beaches untileight years after the tsunami (see Figures 7c–f). The DSAS-based LRR and EPR resultsindicate that only a few of the beaches reached their former positions (Figures 4 and 5). Thepace of the beach recovery is comparatively much slower than other tsunami-affected areasreported elsewhere. The beaches at Phang-nga, Thailand, and the Aceh coast, Sumatra,recovered quickly (within two years) after the tsunami (Choowong et al. 2009; Liew et al.

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Figure 6. Erosion of the coastal inlet at Trinkat Island: (a) 27 February 2004 (pre-tsunami); (b) 4January 2005 (post-tsunami, including the widening of inlet); (c) and (d) 2006 and 2013 images thatcapture the removal of vegetation, erosion of coastal land, suspended sediments and exposed rockbeds.

Figure 7. Straight beaches along the east coast of Trinkat Island: (a) February 2004 (pre-tsunami)and (b) January 2005 (post-tsunami erosion of beaches). (c) April 2006, (d) February 2007, (e)January 2008 and (f) June 2013 depict the recovery of the beaches and deposition of sand.

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Figure 8. Bay headland erosion during various periods. (a) February 2004 captures the pre-tsunamiperiod. (b) January 2005 and (c) April 2006 are post-tsunami periods that depict the eroded bay andremoval of wetlands. (d) February 2007, (e) January 2008 and (f) June 2013 capture the continuederosion in the bay headlands.

2010). Choowong et al. (2009) attributed the fast rate of sediment deposition at Phang-ngacoast to the widening of the tidal inlet and channel banks, which created a large space toaccommodate new sediments. This outcome is not observed within the present study area;the sand for the recovery of the beaches appears to have come from the much eroded westcoast or from the sea. Hence, the recovery process of building the new beaches is quiteslow. Liew et al. (2010) confirm the possibility of building new beaches with sand that wastransported from the sea.

4.3.3. Bay head-lands. The west coast of Trinkat Island is rocky with a scanty sandenvironment. The morphology of the northwest bay land area is one of the most destroyedenvironments of the island. The tsunami waves, which devastated vegetated areas andcut the bedrock, may have entered the bay through the two main inlets. A comparison ofsatellite images for 2004 and 2005 indicates large-scale changes in the bay-land morphology(Figures 8a and 8b). In general, the process of coastal land recovery between 2006 and2013 was not pronounced (Figures 8c–f). Instead, further erosion was recorded during thisperiod. Therefore, the present day coast is marked with relatively deeper bays.

4.4. Implications and Limitations of the Study

The geomorphic response of Trinkat Island to the tsunami after 26 December 2004 is notwell understood. Previous studies on the Nicobar Islands were constrained to the ecologicaland biodiversity impacts, particularly on coral reefs and wetlands (e.g., Bahuguna et al.

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2008). However, a significant outcome of the 2004 tsunami over Trinkat Island is severeshoreline erosion. The results of this study indicate that within a short time span, a large area(4.64 km2) of the island was eroded. Results of NSM indicate that shoreline has moved anaverage of approximately −128 m landwards after the great tsunami. Though we deal withshort-term analysis, NSM provided an insight to the extent of damage to Trinkat Island.EPR for 2004–2005 observed is as high as approximately −500 m/yr at certain transects(Figure 4d). This can be attributed to the direct influence of tsunami waves. Higher valuesof LRR and EPR (2005–2013) (Figures 4b and 4c) suggest consequence of 2004 tsunami.Based on our results, we assume that the natural rates of shoreline movement at TrinkatIsland increased manifold after the 2004 event. The shoreline movement of hundreds ofmeters, the alarming retreat rates and a visual investigation of satellite images indicate thatTrinkat Island is geomorphically vulnerable to erosion and at risk to instability in the future.

Although shoreline extraction and estimation of the erosion-accretion rate were con-ducted, several variables that were not considered in our estimation likely affected theaccuracy of the results. Crowell et al. (1991), Theiler and Danforth (1994), Romine et al.(2009), and others identified typical measurement errors associated with shoreline ratesestimation. The principle limitation in this study is arguably the medium resolution ofIRS and Landsat satellite images for the shoreline extraction. Another constraint is theuse of different images at different tidal stages and the accuracy of the tidal information.Therefore, a minimum of 16.5 m (positioning error + greatest tidal effect) of movementis necessary to reliably detect the shoreline rates. As observed from our NSM results, theaverage shoreline movement was approximately −128 m, much larger than the combinedtotal of the positional accuracy error and the greatest tidal effect. Thus, even if we considerthe positional error and the tidal effects, the methodology could still calculate the erosionrate and shoreline movement in this study region.

5. Conclusion

Evidence of coastal erosion-accretion and morphometric changes was obtained by compar-ing satellite data before and after the 2004 tsunami. The study suggests that the post-tsunamiperiod has caused large-scale morphological changes in the form of erosion and accretionat Trinkat Island. The shoreline of Trinkat Island has been changing rapidly since thetsunami. A net loss of the coastal area of 4.64 km2 was calculated after the destructiveevent. Most of the transects along the foreshore revealed the occurrence of significant ero-sion. Erosion rates as high as −49 m/yr were observed on the island, whereas the accretionrates were comparatively low (approximately +8.5 m/yr). Quantitative estimation of thecoastal land area and visual interpretation of satellite images reveals that the eroded landwas a direct result of tsunami waves. The morphological responses were mainly observedin three coastal geomorphic environments: inlets, straight beaches and bay headlands. Theinlets and bay headlands were further eroded by normal waves and currents after the mainevent. The straight beaches recovered after eight years; however, they did not recover tothe previous position. We conclude that the shoreline of Trinkat Island is more highlydynamic in response to erosion than to accretion. Continued monitoring and assessmentsare recommended to understand the island stability and erosion in the future.

Acknowledgements

The authors thank anonymous reviewers and Dr. Rodolphe Devillers for their valuablecomments and suggestions, which helped to improve the quality of the paper.

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References

Apel, J. R., D. R. Thomson, D. G. Tilley, and P. Van Dyke, 1985. Hydrodynamics and radar signaturesof internal solitons in the Andaman Sea. John Hopkins APL Technical Digest 6(4): 3330–3337.

Bahuguna, A., S. Nayak, and D. Roy, 2008. Impact of the tsunami and earthquake of 26th De-cember 2004 on the vital coastal ecosystems of the Andaman and Nicobar Islands assessedusing RESOURCESAT AWiFS data. International Journal of Applied Earth Observation andGeoinformation 10(2): 229–237.

Bilham, R., 2005. A flying start, then a slow slip. Science 308(5725): 1126–1127.Choowong, M., S. Phantuwongraj, T. Charoentitirat, V. Chutakositkanon, S. Yumuang, and P.

Charusiri, 2009. Beach recovery after 2004 Indian Ocean tsunami from Phang-nga, Thailand.Geomorphology 104(3): 134–142.

CRISP, 2004. http://www.crisp.nus.edu.sg/tsunami./ Last accessed 29 November 2013.Crowell, M., S. P. Leatherman, and M. K. Buckley, 1991. Historical shoreline change: Error analysis

and mapping accuracy. Journal of Coastal Research 7: 839–852.Crowell, M., and S. P. Leatherman, 1999. Coastal erosion mapping and measurement. Journal of

Coastal Research 28: 1–196.Dolan, R., B. Hayden, C. Rea, and J. Heywood, 1979. Shoreline erosion rates along the middle

Atlantic coast of the United States. Geology 7(12): 602–606.Dolan, R., M. S. Fenster, and S. J. Holme, 1991. Temporal analysis of shoreline recession and

accretion. Journal of Coastal Research 7: 723–744.Fletcher, C., J. Rooney, M. Barbee, S. Lim, and B. Richmond, 2003. Mapping shoreline change using

digital orthophotogrammetry on Maui, Hawaii. Journal of Coastal Research 38: 106–124.Ford, M., 2011. Shoreline changes on an urban atoll in the central Pacific Ocean: Majuro Atoll,

Marshall Islands. Journal of Coastal Research 28(1): 11–22.Ford, M., 2013. Shoreline changes interpreted from multi-temporal aerial photographs and high

resolution satellite images: Wotje Atoll, Marshall Islands. Remote Sensing of Environment 135:130–140.

Himmelstoss, E. 2009. DSAS 4.0 installation instructions and user guide. In Digital shoreline analysissystem (DSAS) version 4.0: An ArcGIS extension for calculating shoreline change, ed. E. R.Thieler, E. A. Himmelstoss, J. L. Zichichi, and A. Ergul. U.S. Geological Survey Open-FileReport 2008-1278.

Kench, P. S., R. F. McLean, R. W. Brander, S. L. Nichol, S. G. Smithers, M. R. Ford, K. E. Parnell,and M. Aslam, 2006. Geological effects of tsunami on mid-ocean atoll islands: The Maldivesbefore and after the Sumatran tsunami. Geology 34(3): 177–180.

Lay, T., H. Kanamori, C. J. Ammon, M. Nettles, S. N. Ward, R. C. Aster, S. L. Beck, S. L. Bilek, M.R. Brudzinski, and R. Butler, 2005. The great Sumatra-Andaman earthquake of 26 december2004. Science 308(5725): 1127–1133.

Li, R., K. Di, and R. Ma, 2003. 3-D shoreline extraction from IKONOS satellite imagery. MarineGeodesy 26(1–2): 107–115.

Liew, S. C., A. Gupta, P. P. Wong, and L. K. Kwoh, 2010. Recovery from a large tsunami mappedover time: The Aceh coast, Sumatra. Geomorphology 114(4): 520–529.

Meilianda, E., C. M. Dohmen-Janssen, B. H. Maathuis, S. Hulscher, and J. P. Mulder, 2010. Short-term morphological responses and developments of Banda Aceh coast, Sumatra Island, Indonesiaafter the tsunami on 26 December 2004. Marine Geology 275(1): 96–109.

Meltzner, A. J., K. Sieh, M. Abrams, D. C. Agnew, K. W. Hudnut, J. Avouac, and D. H. Natawidjaja,2006. Uplift and subsidence associated with the great Aceh-Andaman earthquake of 2004.Journal of Geophysical Research: Solid Earth (1978–2012) 111(B2).

Mobile Geographics LLC. Andaman Islands tide chart. http://tides.mobilegeographics.com/locations/4865.html. Last accessed 29 November 2013.

Narayana, A. C., R. Tatavarti, N. Shinu, and A. Subeer, 2007. Tsunami of December 26, 2004 onthe southwest coast of India: Post-tsunami geomorphic and sediment characteristics. MarineGeology 242(1): 155–168.

Dow

nloa

ded

by [

Uni

vers

ity o

f T

okyo

] at

17:

12 1

0 D

ecem

ber

2014

Morphological and Shoreline Changes at Trinkat Island 39

Narayana, A. C. 2011. Tectonic geomorphology, tsunamis and environmental hazards: reference toAndaman-Nicobar Islands. Natural Hazards 57(1): 65–82.

NASA, 2007. New NASA imagery sheds additional perspectives on tsunami. http://www.nasa.gov/vision/earth/lookingatearth/tsunami-images.html. Last accessed 29 November 2013.

NIC, 2011. Basic statistics of Andaman and Nicobar Islands 2010–2011. http://www.and.nic.in/stats/BasicStatistics/index.htm. Last accessed 29 November 2013.

Pardo-Pascual, J. E., J. Almonacid-Caballer, L. A. Ruiz, and J. Palomar-Vazquez, 2012. Automaticextraction of shorelines from Landsat TM and ETM multi-temporal images with subpixel pre-cision. Remote Sensing of Environment 123: 1–11.

Paris, R., P. Wassmer, J. Sartohadi, F. Lavigne, B. Barthomeuf, E. Desgages, D. Grancher, P. Baumert,F. Vautier, and D. Brunstein, 2009. Tsunamis as geomorphic crises: Lessons from the December26, 2004 tsunami in Lhok Nga, west Banda Aceh (Sumatra, Indonesia). Geomorphology 104(1):59–72.

Paris, R., J. Fournier, E. Poizot, S. Etienne, J. Morin, F. Lavigne, and P. Wassmer, 2010. Boulder andfine sediment transport and deposition by the 2004 tsunami in Lhok Nga (western Banda Aceh,Sumatra, Indonesia): a coupled offshore–onshore model. Marine Geology 268(1): 43–54.

Perry, R. B., and G. R. Schimke, 1965. Large-amplitude internal waves observed off the northwestcoast of Sumatra. Journal of Geophysical Research 70(10): 2319–2324.

Romine, B. M., C. H. Fletcher, L. N. Frazer, A. S. Genz, M. M. Barbee, and S. Lim, 2009. Historicalshoreline change, Southeast Oahu, Hawaii; applying polynomial models to calculate shorelinechange rates. Journal of Coastal Research 25(6): 1236–1253.

Ruggiero, P., G. M. Kaminsky, G. Gelfenbaum, and B. Voigt, 2005. Seasonal to interannual mor-phodynamics along a high-energy dissipative littoral cell. Journal of Coastal Research 21(3):553–578.

Theiler, E., and W. Danforth, 1994. Historical shoreline mapping (I): Improving techniques andreducing position errors. Journal of Coastal Research 10(3): 549–563.

Thieler, E., E. A. Himmelstoss, J. L. Zichichi, and A. Ergul, 2009. Digital shoreline analysis system(DSAS) Version 4.0: An ArcGIS extension for calculating shoreline change. U.S. GeologicalSurvey Open-File Report 2008-1278.

Thom, B., and W. Hall, 1991. Behaviour of beach profiles during accretion and erosion dominatedperiods. Earth Surface Processes and Landforms 16(2): 113–127.

Umitsu, M., C. Tanavud, and B. Patanakanog, 2007. Effects of landforms on tsunami flow in theplains of Banda Aceh, Indonesia, and Nam Khem, Thailand. Marine Geology 242(1): 141–153.

Webb, A. P., and P. S. Kench, 2010. The dynamic response of reef islands to sea-level rise: Evidencefrom multi-decadal analysis of island change in the Central Pacific. Global and PlanetaryChange 72(3): 234–246.

White, K., and H. M. El Asmar, 1999. Monitoring changing position of coastlines using ThematicMapper imagery, an example from the Nile Delta. Geomorphology 29(1): 93–105.

Wong, P. P. 2009. Impacts and recovery from a large tsunami: Coasts of Aceh. Polish Journal ofEnvironmental Studies 18: 5–16.

Zhang, K., D. Whitman, S. Leatherman, and W. Robertson, 2005. Quantification of beach changescaused by Hurricane Floyd along Florida’s Atlantic coast using airborne laser surveys. Journalof Coastal Research 21(1): 123–134.

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