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Management of Coral Reefs in Gulf of Mannar using Remote Sensing and GIS Techniques – with Reference to Coastal Geomorphology and Land Use
2. Objectivs of the Study
The objectives of the present study are to
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Assess the current status of coral reefs in Gulf of Mannar based on remote sensing and GIS approach
- Assess the changes that have occurred in the spatial distribution of coral reefs during the period 1988-1998 using multidate remote sensing data
- Study the coastal geomorphology and its influence on the coral reefs
- Study the influence of landuse/landcover changes on the coral reefs
- Suggest suitable management measures for sustainable management and preservation of coral reefs in Gulf of Mannar region
3. Materials and Methods
Images of IRS LISS-II (April 1988) and IRS LISS-III (May 1998), Survey of India Toposheets (1969) and Naval Hydrographic Charts (NHO) 1975 were been used in this study.
To cover the objectives of this study, six types of approaches have been attempted are listed below:
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Analyse and interpretation of optical remote sensing data (IRS LISS-III data) for coastal geomorphology
- Analyse and interpretation of optical remote sensing data (IRS LISS-III data) and Survey of India Topographic sheets (1969) for shoreline change mapping.
- Interpolation of Bathymetry using Naval Hydrographic charts and bathymetry survey
- Analyse and interpretation of multidate optical remote sensing data (IRS LISS-II and LISS-III data) for coastal land use/land cover change deduction
- Socio-economic studies
- Analyse and interpretation of multidate optical remote sensing data (IRS LISS-II and LISS-III data) for coral reef change deduction.
Coastal Landform mapping
Geocoded IRS1D LISS – III imagery on 1:50,000 scale were visually interpreted based on image characteristics, and identified and mapped various coastal landform categories along the coast of Gulf of Mannar. In the present study, an image interpretation key indicating tone/colour, size and pattern developed by Space Applications Center, Ahmedabad SAC (1991), has been adopted in this study. The basic information like transport network, tanks, rivers etc are transferred from SOI toposheet. After identification and delineation, an accuracy test was made for 118 sample points on SOI toposheet. The study area map at 1:50, 000 scale was divided into grids and intersecting points of each grid within the study area were taken as sample points for validation of classified satellite data in ground truth checking. Over the ground, out of the 118 sample points, 105 points were found to be correctly interpreted giving an accuracy of about 90 per cent. The georeferenced coastal land form map was digitized, edited labeled and projected using ARC-INFO GIS. Finally a coastal landform map was generated using intercept operation of ARC/VIEW. The area statistics of coastal landforms in the map were generated.
Shoreline Change
Geocoded IRS LISS III data of May 1998 and SOI topographic sheets of 1969 were used to prepare shoreline maps on 1:50,000 scale. Multi-date shoreline maps of 1969 and1998 were digitized and projected using polygonal using ARC-INFO GIS and were overlaid using tic coordinates of the study area. Overlaid maps were edited and labeled. Finally a temoporal shoreline change map was generated using intercept option of ARC-VIEW and and identified erosion and accretion areas along the coasts of island and offshore islands in Gulf of Mannar wit sufficient ground truth verification.
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