Evaluating Coastal Tourism Potential and Environmental Constraints Using Geospatial Decision-Making Techniques: Evidence from Trincomalee, Sri Lanka

Coastal tourism plays a significant role in Sri Lanka’s economy; however, rapid, unplanned tourism development threatens fragile coastal ecosystems. This study evaluates coastal tourism suitability and environmental vulnerability in the Trincomalee District using a GIS-based Multi-Criteria Decision Analysis (MCDA) integrated with the Sustainable Coastal Tourism Suitability Index (SCTSI). The primary objective was to identify areas suitable for tourism development while ensuring the protection of ecologically sensitive coastal environments. Multiple geospatial datasets, including Sentinel-2 imagery, land use/land cover data, road accessibility, built-up density, coastal erosion risk, coral reefs, mangroves, and seagrass distributions, were processed using Google Earth Engine and GIS analytical techniques. Thematic layers were standardized and integrated using a weighted overlay approach informed by AHP criteria weights. The findings indicate that only 12% (327 km²) of the district is highly suitable for tourism development, while 30% (818 km²) is classified as suitable and 32% (873 km²) as moderately suitable. Environmentally sensitive and restricted areas, including coral reefs, mangrove ecosystems, seagrass habitats, and erosion-prone coastlines, account for approximately 9% (245 km²) of the study area. The SCTSI model refined conventional MCDA outputs by incorporating environmental constraint penalties, thereby emphasizing environmentally responsible tourism planning. The study recommends prioritizing tourism development within high-suitability zones that already possess adequate infrastructure accessibility, while ensuring strict conservation of ecologically fragile coastal ecosystems. The integrated geospatial framework developed in this study provides an effective decision-support tool for sustainable coastal tourism planning and can be adapted to other rapidly developing coastal regions facing similar environmental pressures. Keywords: Coastal tourism, Environmental Vulnerability, Multi-Criteria Decision Analysis (MCDA), Sustainable Coastal Tourism Suitability Index (SCTSI), Sustainable tourism