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Monitoring Changes in Seafloor Morphology Using Multi-date Bathymetry data: A Case Study of the Gulf of Mannar, Southeast Coast of India
 Dr. M. Thanikachalam Senior Lecturer, Department of Civil, Mepco Schlenk Engineering College, Sivakasi-626 005  Prof. S. Ramachandran Director, Institute for Ocean Management, Anna University, Chennai-600 025 India aisuwariyaa@yahoo.com 1. Introduction Any changes in sea floor may be the result of sea-level variation or to a change in the elevation of land surface. Changes in absolute water-surface levels are worldwide due to the interconnectivity of the oceans and are termed eustatic changes. Changes in the absolute level of the land are localized. They may be due to tectonic adjustments or due to adjustments caused by their distribution of weight on the land surface. As and when sedimentation or ice build-up occurs, such changes are known as isostatic. A rise in the sea level or down warping of land would involve the opposite movements of sea and land. Synonymous with positive and negative changes are the forms of sea-level transgression and regression, although in many cases these terms also refer to the horizontal movement of the shoreline associated with vertical changes of sea level. Indian shore has experienced submergence and emergence due to global as well as local oscillations of the sea level by multivariate tectonic, fluvial and marine geomorphic processes. The repeated emergence and submergency of coast have been instrumental in shaping the morphological expressions of the continental shelves in general and shoreline in particular (Jayaprakash et al. 2002).Thanikachalam and Ramachandran, 2002 proved that the coast is going on emerging by tectonic movement. There is a remarkable difference in the extent of continental shelf of the east coast of India when compared to west coast of India. The shelf on the west coast is broad with thin layer of sediment, while the eastern shelf is narrow with thick layer of sediment (Agarwal 1990). The main objective of the paper is to generate the bathymetry maps using multi date bathymetry data and identify the morphology of sea floor and its changes. 2. Study Area The study area (Figure 1), Gulf of Mannar, extending from Tuticorin to Rameswaram island in the SW-NE direction, lies between 78º 5’ & 79º30’ E longitudes and 8º47’ & 9º15’ N latitudes, to a length of about 140 km. There are 21 islands, situated at an average distance of about 8 km from the coast and running almost parallel to the coastline. This area is endowed with a combination of ecosystems including mangroves, seagrass, seaweeds and corals reefs. Different types of reef formations have also been observed in Gulf of Mannar viz. fringing reef, patch reef and coral pinnacles. The coast of Gulf of Mannar is mostly underling by Quaternary to Recent formation. The west of this coastal area is bound by heavy crystalline metamorphic rocks of Pre Cambrian and having breath of 10-100 km (Ramasamy 1997). Being a gradient coast it has developed well fabricated network of deltas, backwater, creeks, protruding deltas, estuaries, back swamps and coral reef etc.  Figure 1. Location Map of Gulf of Mannar
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