INTERNATIONAL JOURNAL OF GEOMATICS AND GEOSCIENCES Volume 5, No 4, Copyright by the authors - Licensee IPA- Under Creative Commons license 3.

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1 INTERNATIONAL JOURNAL OF GEOMATICS AND GEOSCIENCES Volume 5, No 4, 2015 Copyright by the authors - Licensee IPA- Under Creative Commons license 3.0 Research article ISSN Assessment of shoreline changes along Nagapattinam coast using geospatial techniques Mageswaran T 1, Ram Mohan V 1, Chenthamil Selvan S 1, Arumugam T 1, Tune Usha 2 and Kankara R.S Department of Geology, University of Madras, Chennai Integrated Coastal and Marine Area Management (ICMAM) project Directorate, Ministry of Earth Sciences, Pallikaranai, Chennai magesh.presidency@gmail.com ABSTRACT Coastal erosion is one of the major issues in world coastline. Its impact has adversely affects the livelihood of the coastal community. The coastal zone of India is experiencing a wide range of natural and anthropogenic pressure. This study was carried out along the Nagapattinam district of Tamil Nadu, India using multi-temporal satellite images from 1978 to The long-term coastal erosion and accretion rates have been calculated using Digital Shoreline Analysis System (DSAS). Linear regression rate (LRR) statistical method is applied to estimate the shoreline change rate. The results of the analysis shows that erosion is dominant in Sirkali, Tharangambadi, Karaikal (Puducherry State) and Nagapattinam taluks, while Thiruthuraipundi taluk is undergoing accretion. Both natural and anthropogenic processes along the coast control the erosion and accretion activities of the coastal zones. The present study demonstrates that combined use of satellite imagery and statistical methods can be a reliable method for shoreline change analysis. Keywords: Shoreline; Remote Sensing & GIS; Erosion; Accretion; DSAS; Nagapattinam 1. Introduction Shoreline is the boundary between land and sea keeps changing its position continuously due to dynamic environmental conditions. It is one of the most rapidly changing landforms of the earth (Chorly et al., 1984) and the changes depend on geology, geomorphology and wave action along the coastline; periodic storms; changes in sea-level; sediment transport by longshore currents and anthropogenic activities (Carter and Woodroffe, 1994; Cowell and Thorn, 1994; Pidwirny, 2006; Fanos et al., 1995; Berger and Lams, 1996; Ibe, 1998; Pandian et al., 2004; Dey et al., 2002). The changes in shoreline often result in coastal erosion or accretion, depending on the dominant processes acting on the coastline. Erosion is one of the major issues in world coastline, particularly for a country like India facing explosive population growth. About 23 % of the Indian coast (Sanil Kumar et al., 2006) is affected by various degree of erosion in several pockets resulting in loss of beaches and consequently to set back of the coastline that threatens the coastal communities. Therefore, accurate demarcation and monitoring of shorelines are essential for all the coastal infrastructure projects and sustainable coastal zone management. Submitted on January 2015 published on May

2 Traditionally, the shoreline mapping is carried out using conventional field surveying methods (Ingham, 1992) or on interpretation of aerial photographs (Lillesand and Kiefer, 1987, Dolan et al., 1980). In the recent years, remote sensing data has been widely used in shoreline change studies because of their synoptic and repetitive data coverage, high resolution, multispectral capabilities and its cost effectiveness in comparison to conventional techniques. In India, shoreline change studies have successfully investigated using remote sensing and GIS by many researchers at different times (Shailesh Nayak, 2002; Alesheikh et al., 2007; Chandrasekar et al., 2011; Srinivasa Kumar et al., 2008; Charatkar, 2004; Murali et al., 2009; Kaliraj et al., This study investigates the coastal erosion and accretion variation in long-term scenario using multi-temporal satellite imageries with the aid of Digital Shoreline Analysis System (DSAS). The results of the study will be more informative for erosion hazard management in Nagapattinam district of Tamil Nadu. 2. Study area The coastal belt investigated for the present study is Nagapattinam district (Fig.1) of Tamil Nadu state, India lies on the shore of Bay of Bengal. This district has a coastal length of 187 km including a stretch of 17 km in Karaikkal. The study area starts from Kodiyampalayam in the north to Kodiyakkarai point (Point Calimer) in the south falls within Latitude of 10 16' 31.21" to 11 23' 12.08" and Longitude of 79 49' 14.94" to 79 49' 42.83". Rivers such as Vennar, Uppanar, Araslar, Nadalar, Thirumalairajan, Puravadaiyanar, Vettar and Vellar rivers flowing in this district. The climate is sub-tropical humid and the average annual rainfall ranges from 950 to 1500 mm. The wave activity is significant both during southwest and northeast monsoons but extreme wave conditions occur under severe tropical cyclones. The chief rock type of this region is tertiary rocks which is equivalent to Cuddalore sandstones overlying the crystalline Precambrian rocks. Because of the long coastal length, the study area has been divided into 4 discrete zones (table. 1) on the basis of taluk wise for shoreline change analysis. Figure 1: Study area 556

3 3. Data used Table 1: Zone Numbers and corresponding DSAS transects The long-term shoreline change assessment to Nagapattinam coast is studied for a period of 35 years from Shoreline change evaluations are based on comparing six historical shorelines extracted from different satellite imageries. Multi-temporal satellite data of Landsat (MSS, TM & ETM+) were downloaded freely from the website & for the period 1978, 1990, 2000, 2006, 2010 and The details regarding satellite and their acquisition dates are listed in table 2. Table 2: Details of the satellite data and their acquisition dates S.No Satellite/Sensor Path/row Zone Number LANDSAT 2 (MSS) LANDSAT 5 (TM) LANDSAT 7 (ETM +) LANDSAT 7 (ETM +) LANDSAT 7 (ETM +) LANDSAT 8 (ETM +) 4. Methodology Zone DSAS Transect Numbers Spatial resolution Producer Coastal Length(km) 1 Sirkazhi taluk Tarangambadi taluk & Karaikkal (UT) Nagapattinam taluk Tirutturaippundi taluk Acquisition Date 152/52,152/53 60 m USGS 23/06/ /52,142/53 30 m USGS 29/01/ /52,142/53 30 m USGS 28/10/ /52,142/53 30 m USGS 03/09/ /52,142/53 30 m USGS 18/02/ /52,142/53 30 m USGS 18/05/2013 Downloaded satellite images are projected to UTM projection with zone 44 North and WGS 84 datum. Initially, the satellite image of the period 2000 is geo-referenced based on the ground control points (like road intersection, buildings/permanent features) collected from the field using handheld GPS. Then, the other periods of satellite images were rectified using 2 nd order polynomial image to image rectification technique in ERDAS IMAGINE 9.1 software. False Color Composites (FCC) is generated using band combination for the satellite imageries which nicely depicts water-land interface. Further, image enhancement technique is carried out for satellite images for better visualization and delineation of shoreline. The 557

4 shorelines were drawn through on-screen digitaization using visual interpretation technique in ArcGIS software. The multi-date shorelines were given as input in Digital Shoreline Analysis System (DSAS) to calculate the shoreline change rate (USGS, 2005). Transects were generated using DSAS to 1 km length with 50m spacing to study the changes occurred along Nagapattinam coast. Field verification is also carried out to check the current shoreline positions using hand held GPS in few locations and photographs was also documented. 5. Results and discussions The present study adopted the statistical method Linear Regression Rate (LRR) to calculate the shoreline change rate using DSAS. For the zone 1 (Sirkazhi taluk), rate of change was measured along 33 km of shoreline and observed both erosion and accretion, but majority of the transect shows erosion. The net rate, averaged over 667 transects, was 1.08 m/year along those transects with erosion trend; the average erosion rate was 1.98 m/year and was found along 72% of Sirkazhi taluk. The average accretion rate, which occurred along 28% of the coast, was 1.26 m/year. Erosion is reported along Tirumullaivasal, Akkaraipettai, Kodaikkadu, Poompuhar while accretion is observed along Kodiyampalaiyam and Tandavankulam. In zone 2 (Tarangambadi taluk and Karaikkal UT), the shoreline change rate shows negative trend throughout the zone except few transects (Fig. 2). The net rate, averaged over 610 transects, was 0.70 m/year along those transects with erosion trend. The average erosion and accretion rate was 1.13 m/year and 0.41 m/year respectively. Out of 610 transects in zone 2, 443 records erosion and 167 records accretion. Erosion is observed along transects of Pattanacheri and Nagore coast whereas Akkampettai shows accretion. Transect along northern part of Tarangambadi shows erosion and southern part shows accretion. Similar observation is reported along Tarangambadi coast by Saranathan et al (2011) that the southern part is characterized by the confluence of the two major rivers namely Nandalar and Uppanar river. But, soon after Tsunami, the central and southern portion is characterized by deposition from 2004 to For zone 3 (Nagapattinam taluk), the shoreline change analysis shows both erosion and accretion trend but erosion is significant. In this zone, the average erosion and accretion rate was 0.99 m/year and 0.89 m/year respectively. Erosion is observed along transect of Nagapattinam, Akkaraipettai and Velankanni villages while accretion is seen along Tiruppundi kil setti. In the zone 4 (Tirutturaippundi taluk), the average accretion rate was 1.96 m/year and was found along 82.5% of the coast. Villages like Pusphavanam, Vedaranyam and Kodiyakkarai shows accreting trend (Fig. 3). In zone 4 totally, 486 transects records accretion and 104 transects records erosion. Zone 4 is predominantly dominated by accretion and might be attributed by very shallow near shore bathymetry, less wave current velocity and wave height along this region. Considering the maximum and minimum values of the shoreline change rate, the coastline of Nagapattinam district is divided into five categories (Fig. 4). Out of 123 km coastal length studied moderate erosion occupied 50 km of the coast followed by moderate accretion (30 km), stable coast/no change (29 km), high accretion (8 km) and high erosion(6 km) respectively. Erosion is the dominant class in Zone I, II & III (Sirkazhi, Tarangambadi and Nagapattinam taluk), whereas Zone IV (Tirutturaippundi taluk) undergoes accretion (Table. 3). 558

5 Figure 2: Graphical representation of zone 1, 2 & 4 using LRR method Table 3: Results of Shoreline change rate on zone wise using LRR Total Number of Transect Shoreline Length(km) Mean shoreline change rate (m/yr) Mean erosion rate (m/yr) Mean accretion rate (m/yr) Shoreline Change Rate (Minimum) Shoreline Change Rate (Maximum) Total Transect that Record Erosion Total Transect that Record Accretion Zone wise overall Trend Erosion Erosion Erosion Accretion 559

6 5. Conclusion Figure 3: Shoreline change map ( ) This study clearly demonstrates that the integration of remote sensing and GIS technology is very useful for long term shoreline change studies with reasonable accuracy. Further, this study can be carried out using high resolution satellite images or RTK GPS surveys, so that the shorelines can be demarcated more accurately. Both natural (littoral drift, tidal action, near shore bathymetry) and anthropogenic activities (construction of seawalls, groins or 560

7 breakwaters) along the coast modify the shoreline configuration and control the erosion and accretion of the coastal zones. The result of shoreline change map will be more useful for coastal engineers and coastal zone management authorities to facilitate suitable management plans and regulation of coastal zones. Acknowledgements Figure 4: Different classes of shoreline along Nagapattinam We would like to express our sincere thanks to Dr. B R Subramanian, Former Project Director, ICMAM, Ministry of Earth Sciences and Prof. S.P. Mohan and University of Madras, Project Fellowship in MoES project for their constant encouragement and support. 6. References 1. Alesheikh, A. A., Ghorbanali, A., and Nouri, N., (2007), Coastline change detection using remote sensing, International Journal of Environment Science and Technology, 4, pp Carter, R.W.G., and Woodroffe, C.D, (1994), Coastal evolution: Late quaternary shoreline morphodynamics. Cambridge: Cambridge University Press, p Charatkar, S.L., Mitra, D., Biradar, R.S., and Radhakrishnan, K.V, (2004), A study of erosion and accretion along Gulf of Khambat, Gujarat coast using remote sensing and GIS. AFITA/WCCA, Joint Congress on Agriculture, Bangkok, Thailand, pp Chorly, R.J., Schemm, S.A., and Sngden, D.E., (1984) Geomorphology. Methuen, London, p Cowell, P.J. and B.G. Thorn., (1994). Morphodynamics of coastal evolution. In: Carter, R.W.G. and Woodroffe, C.D., (eds.), Coastal Evolution. Cambridge: Cambridge University Press, pp Dey, S., Dutta, S., and Adak, S.B., (2002), Holocene sea level change of West Bengal Coast. Indian Geogr. J 77(1), pp Dolan, R., Hayden, B.P., May, P., and May, S. K., (1980), The reliability of shoreline change measurements from aerial photographs. Shore and Beach, 48(4), pp

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