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Comparison Of Coastal Change Of The Gulf Of Thailand And The Andaman Sea: Case Study In Nakhon Si Th

4953,2926,4954,4955

Thailand has an extensive coastal area covering 23 provinces of eastern Gulf of Thailand coast of the Pacific Ocean and western Andaman Sea coast of the Indian Ocean. Thailand comprises extensive coastline totaling about 2,637 kilometers in length (DMR, 2002). The Gulf of Thailand coasts cover 1,700 kilometers and the Andaman Sea coasts cover 937 kilometers. These coastal zones are endowed with rich natural resources and are, therefore, important for economic development of the country. In the past, the coastlines have been changed mainly by natural processes. At present, the coasts of Thailand have been severely changed. The coastal problems caused by the changes include beach pollution, coastal erosion, reduction of coastal wetland, and reduction in sediment supply.
In the gulf of southern Thailand, the coast of Nakhon Si Thammarat province is about 190 kilometers in length and it lies within the Khanom, Sichon, Tha Sala, Muang, Pak Panang and Hua Sai districts. In the Andaman Sea, the coast of Trang province is about 150 kilometers in length and it lies within the Sikoa, Kantang, Hat Samran, and Palian districts.
This study uses the Landsat ETM+ satellite imagery scene 128/54, 129/54 and 129/55 acquired in four periods of 1989, 1994, 2001 and 2004. The SPOT imagery scene 263/332, 263/335, 263/336, and 264/333 acquired in two periods of 2006, 2007. The THEOS imagery scene 263/332, 264/333, and 265/334 acquired in two periods of 2007 and 2009. In this study image transformation techniques are used for classification of land and water or coastline by using ENVI program and GIS technique.
The satellite images are processed and analysed by using The Normalized Difference Water Index (NDWI), decision tree classification and field investigation. The NDWI method would reveal the water body and the land body. The NDWI value is applied to use in decision tree classification and the best value for classify is 0.25. Then the decision tree classification is used for indicating coastline and field investigation for recheck the coastline analysis.
The classification of land and water and the mapping of coastline of two periods have been accomplished by using the remote sensing technique. In Nakhon Si Thammarat province the coastal erosion is severe and affected more than 60 kilometers long. The prominent coastal erosion area is in Ban Laem Talumphuk and Ban Ao Bon with the rate of 4.48 meters per year and 8.79 meters per year respectively during 2004 to 2007. In Trang province the coastal erosion is severe and affected about 25 kilometers long. The main coastal erosion area covers Hat Ratcha Mongkhon and Hat Pak Meng with the rate of 1.92 meters per year and 1.70 meters per year respectively during 1989 to 2001.