Mapping of coastal eco system using Remote Sensing and spatial technology - experience from South India  Dr. S. M. Ramasamy Professor & Director, Centre for Remote Sensing Bharathidasan University, Tiruchirappalli smrsamy@hotmail.com Abstract The coastal eco system is very complex and fragile because of the multivariate dynamically active and pulsatory tectonic and geomorphic processes. As remote sensing provides potential information on the pattern and the splay of geomorphic features, which stand as a testimony for the past and present eco system, fabrication of the eco system was made for Tamil Nadu coast using the remote sensing techniques. These information were subsequently animated using PC Arc/info. Introduction The coastal eco system is unique, self styled and divergent owing to the multivariate tectonic, fluvial, coastal and aeolian geomorphic processes. These processes which have acted in varying degrees and duration during the Quaternary period have left their imprints in the form of various geomorphic features along the coast such as deltas of different morphology (lobate, arcuate, cuspate, digitate and estuarine), beach ridge complexes, backwater-lagoon systems, estuary and creek systems, spit systems etc. Hence, once these features and there from the geomorphic processes are mapped using technologies like remote sensing not only the present eco system but also the palaeo eco system right from approximately 1.5 million years to today can be fabricated. In such a fabrication spatial technology plays significant role.
The Tamil Nadu coast is one such a coast which stands as a testimony for the coastal eco system of the Quaternary period and its temporal changes during the past nearly one million years or so. As remote sensing provides excellent information on the pattern and the spatial distribution of these geomorphic features and the spatial technology has unique capabilities, these were utilised in mapping the eco system of Tamil Nadu coast and some of the salient cases are briefly presented in this paper. Tectonic Scenario The studies carried out by various workers in general and the present author and his research team in particular have brought out detailed information that the Indian Peninsular is tectonically active with
 Fig 3 Geomorphology  These tectonic forces which have generated well defined arches in Chennai and Ramanathapuram - Rameswaram areas (Fig. 1) with intervening deeps in Ponnani - Manamelkudi area and the N-S faulting in Tanjore region have played a significant role in controlling the geomorphic processes, evolution and therefrom the eco system of the area. As a result deltas with multivariate morphology were formed in Palar, Ponnaiyar, Cauvery, Vaigai and other rivers. (Fig. 2) along Tamil Nadu coast.
In areas of cymatogenic arching in Chennai and Ramanathapuram - Rameswaram region (Fig. 1, 2) beach ridges are found in wider breadth of 3 to 40 km. On the contrary, the beach ridges found to a breadth of 50 kms in Point Calimere / Vedaranniyam region (Fig. 1, 2) is attributed to the tectonic emergence of the land along the N-S faults in the area east of Tanjore. That is because of the tectonic emergence, the land has slowly prograded pushing away the sea gradually. In addition gradual shrinkage in backwater, withdrawal of creeks and estuaries, heavy sedimentation of backwater, sediment discharge into the ocean are found. Whereas in areas of tectonic subsidence (Pondicherry and Manamelkudi) flooding, gradual increase in tidal activities, mangrove spreading and storm surges are witnessed.
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