Thesis (M.Sc.) - Asian Institute of Technology, 2004

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, School of Environment, Resources and Development

Seagrass beds in Thailand have been estimated to cover about 94 km2 . Several studies found that seagrasses coverage and associated biota are degraded and lost in recent years because of a number of factors, mainly due to illegal fishing and land development activities. Nowadays, Thai government has been developing a strategic plan for seagrass management in order to achieve a sustainable development. Krabi estuary is a part of Phangnga Bay, the Andaman Sea. Seagrass bed occurring in Koh Siboya is the third biggest in Thailand. Nine species of seagrass were recorded in the study area, and the total area of seagrass is more than 10 km2 {u2022} Seagrass beds in Koh Siboya have been using as main fishing ground by local communities. However, these seagrass beds are under threats from fishing activities, channel dredging and land development activities. This study aimed at developing an approach of using high spatial resolution image - IKONOS for developing seagrass bed map. LAI, PCA and FCC models are applied to enhance image. Maximum Likelihood Classification is used for classification. User accuracy of mapping seagrass achieved in this study is 87,9%. Results from image analysis show that the total area of seagrass bed is 9.344 km2 in which the dense seagrass beds coverage 60 - 75% occupy 27% of the area. Moreover, the relationship of environmental data and distribution of seagrass beds is also exploited in this study. In addition, two others satellite images including Landsat TM and ASTER are also used to compare with IKONOS satellite image. Recommendation the guideline of integrated management for seagrass ecosystem include four scenarios: industrial scenario, nature scenario, co-management scenario and education scenario was developed.