Coastal wetland and shoreline change mapping of Pichavaram, south east coast of India using Satellite data Image rectification and restoration Preprocessing operations are intended to eliminate or correct the distortions or errors caused due to geometric distortions, radiometric distortion presence of noise in the data, etc. This standard products made available to the interpreters are preprocessed therefore generally data can be used directly for image enhancement and classification. Image enhancement Operations are being implemented to image data to get the enhanced output for subsequent visual interpretations. The enhancement techniques provide better feature exhibition to increase the visual distinction between features contained in a scene. The enhanced output can be seen in the display or can be recorded in the pictorial form as Black and White (or) colour composite images. Image classification Image classification operations are essentially meant to substitute visual analysis of remotely sensed data with quantitative analysis. The classification of the remotely sensed satellite digital data can be carried out either without a prior knowledge about the features present in the scene is called unsupervised classification and with a prior knowledge about the terrain features interactive classification method is called supervised classification i.e. The user can define the class beforehand the supervised classification is the setting of representative pixel values for each class and classifying another pixel values based on this standard set. In this present study preprocessed satellite (LANDSAT, IRS) were used for Wetland mapping and also supervised classification method were performed using ERDAS Imagine image processing software package.  Wetland Classification Wetland map was classified using available satellite data IRS1C LISS –III (23.5 m spatial resolution) in the year 1998 for the Pichavaram Mangrove areas. The area can be divided into three zones Agriculture zone and Wetland zone with vegetation and Non-Vegetated wetland. Agriculture land is present in the northern part of the Pichavaram area, this delta region formed by rapid deposition of stream borne sediments into a still body of water. The river supplies sand silt and other detrital materials which are deposited. This is very fertile area present in the Cauvery delta region. Flood plains are predominant along the rivers which are linear and parallel to the river course. The standing crop of paddy is almost seen through out the year along the Vellar river course an area of about 116.7 km2. Non vegetated wetland consists of mudflats beach spit and sandbars along the lagoon estuaries and deltaic regions. They are divided into high tidal, inter tidal and sub tidal regions (Davis, 1972). However, at many places, they could not be further categorized. High tidal flat normally have very fine mud with little or no moisture. Large patches of mudflats occur between Uppanar and Coleroon estuaries. It is not possible to delineate inter tidal zone at all the places for the length of 1,486 km2. The beach is located the eastern part of the area near Vellar mouth, the beach area is narrow and at some places sand is replaced by mud. Beach area under erosion in many places spits are observed near Coleroon and Uppanar mouth area one end of the spit is attached to the mainland and other end terminates into the open sea. Mudflats are also in between mangrove vegetation in the hightidal, intertidal and subtidal zone. Mudflats are associated with less wave energy zones. These mud flats are composed of clay and silt and they are exposed during very low tides. Intertidal mudflats are made up of fine grained soft muds which are deposited under quiet environment. The sub-strata are suitable for the growth of mangroves and marsh vegetation. A variety flora and fauna are present in these areas. Most of sand bars are found near the mouth of rivers and therefore called mouth bars. These mouth bars are small in size in the areas of Vellar, Coleroon and Uppanar estuaries. Sand bars are also present in Uppanar backwater areas and fringed with sparse Mangroves. The vegetated wetland has been classified in two types such as Mangroves and tidal swamps in Pichavaram area coastal lagoon covers an area of about 8.4 km2. The entire mangroves area consists of 51 islets which are separated by complex network of creeks. A long sand bar separates the whole area from the sea. Extensive mangrove forest, containing narrow Rizophora belt in the frequently inundated areas is followed by wide belt Avicennia on terrains submerged mostly equinoctial tides. The area that is generally very saline and sandy. Which is submerged only during exceptionally high tides contains mostly Suaeda vegetation. The Pichavaram mangroves area (7.29km2) is declared as reserved forest by state government. The current level of exploitation of Pichavaram mangroves far exceeds sustainable levels, and the habitat is rapidly being degraded. Dense scrub like Avicenia Ilicifolium and Cariops Roxburghianae are mixed with mangroves scrubs are found near Uppanar riverbank and Vellar River, other vegetation such as marsh vegetations, grass, thorny plants and scattered mangroves were classified under this category due to their scattered distribution, it is difficult to separately delineate them, and they are collectively classified as other vegetation with mudflat. Sparse stunted marsh vegetation and degraded mangroves are present on hightidal mudflats near mouth of Vellar river, bank of Uppanar and Near Coleroon riverbank. Salt deposits on mudflats areas mainly along saltpans in Porto Novo near Vellar river saline areas. The marsh vegetation present on the bar which is separating the lagoon from the sea is dense and water logged areas are also present in between. Flood prone areas were delineated near Coleroon river Vellar and the near banks of Uppanar and Coleroon rivers. Lagoons are observed in this area lying parallel to the coastline and separated from the open sea by barrier of islands. These lagoons are connected to the Bay of Bengal by one or more openings. The sub-rivers like Uppanar, Vellar and Coleroon rivers drain into this lagoon. The water level is fluctuating and suspended sediment concentration is high,  Fig. 2.Wetland Map mangrove vegetation is present along the verge of lagoon. Classified output checked with sufficient ground truth verification, hence relevant ground data were collected for verification and field checks were made for doubtful areas necessary corrections were made in the classified output. |