- Situated off the west coast of Vietnam in the Gulf of Thailand, Phu Quoc archipelago and its waters are well-known for their rich natural resources, especially the bounty of fishery resources. Under increasing pressure from the growing population, fishing, and tourism development, there is a strong need to formulate an integrated coastal management plan for Phu Quoc. An integral part of most management techniques is to have detailed maps of these habitats and to monitor their condition. To date, no distribution maps of benthic habitats such as coral reefs and sea grass beds in Phu Quoc exist. There have been only a few efforts to map these habitats such as a series of transect surveys carried out by WWF (World Wildlife Fund) Vietnam Marine Conservation Southern Survey Team in 1994. Remote sensing techniques provide a unique opportunity to map the spatial and temporal distribution of these resources at various scales. This study has at three major components. Firstly, the baseline GIS data of Phu Quoc were generated from a 1:50,000 scale topography map, including: shoreline, rivers, elevational contours, road network, bathymetry, and the DEM (Digital Elevation Model). These data serve as a starting point to formulate a digital database that facilitates future study and resource
management in the area.Secondly, the benthic habitat mapping was focused in three sites surveyed in 1993 and 1994 using Landsat Thematic Mapper (TM) imagery acquired in 1992. To maximize the chance that the upwelling signals recorded by the TM sensor contain useful information about the sea
bottom, the study areas were restricted to a depth less than 6 meters. The image classification and interpretation were conducted on three TM visible bands that were transformed to minimize the depth-dependence variance in the bottom reflectance signal as well the original bands without depth-effect correction. The results indicate that benthic features of large extent such as seagrass
beds off the east coast of Phu Quoc can be mapped using Landsat TM imagery. Future work to validate the classification maps is needed. The third component is to demonstrate how GIS could support marine resources management in Phu Quoc. Coral reefs are susceptible to nutrient excess and sedimentation caused by run-off water. A GIS-based model was developed to assess the environmental sensitivity of coastal watersheds impacting the nearby coral reefs via the sedimentation process. The model
incorporates vegetation cover, terrain steepness, and watershed area, and takes into account the proximity of benthic habitats and estuarine areas. Vegetation cover was extracted from the TM 1992 image. Slope and area by watershed were extracted from the 1969 topographic map. The resulting sensitivity maps could assist coastal managers in making informed decisions on landuse activities to ensure the viability of the nearby coral reefs.