MAPPING LAND SURFACE EMISSIVITY PATTERNS IN A COASTAL WETLAND ENVIRONMENT; A GIS-BASED STUDY OF BAYELSA STATE, NIGERIA

Abstract

Land surface emissivity (LSE) is an important surface parameter influencing long-wave radiation exchange and the retrieval of land surface temperature from satellite data. In many studies within the Niger Delta, emissivity is commonly treated as spatially uniform, despite the region’s pronounced land-cover heterogeneity. This study examines the spatial distribution of land surface emissivity in Bayelsa State, Nigeria, using satellite remote sensing and Geographic Information System (GIS) techniques. The analysis was based on Landsat 8 Operational Land Imager/Thermal Infrared Sensor (OLI/TIRS) imagery acquired in 2020, with a spatial resolution of 30 m for reflective bands and 100 m (resampled to 30 m) for thermal bands. Land surface emissivity was estimated using an NDVI-based emissivity retrieval approach, following established procedures in thermal remote sensing, and the resulting emissivity values were analysed spatially within a GIS environment. The results indicate clear spatial variability in emissivity across Bayelsa State. Very high to high emissivity values (≥0.96) dominate wetlands, mangrove forests, and riverine environments, accounting for approximately 65% of the study area, while low to very low emissivity values (≤0.93) are primarily associated with urbanised and exposed surfaces, representing about 17% of the area. These patterns reflect differences in land cover, surface material properties, and moisture conditions rather than statistically inferred causal relationships. While the observed spatial trends are consistent with patterns reported in previous studies of coastal and wetland environments, this study does not attempt inferential validation. Instead, it provides a baseline, spatially explicit depiction of land surface emissivity in Bayelsa State. The findings highlight the importance of treating emissivity as a spatially variable parameter in environmental analyses and offer foundational information to support future climate-related and land-use studies in the Niger Delta.