Assessment of Urban Heat Island Effect and Green Cover Depletion in Enugu City, South East Nigeria

This study assesses the urban heat island effect and its relationship to green cover depletion in Enugu City, Enugu State, South East Nigeria. Urban heat islands, where developed urban zones record significantly higher temperatures than surrounding rural areas, are increasingly documented in Nigerian cities as impervious surface coverage expands and urban vegetation is cleared for development. Landsat satellite imagery from 2018 and 2023 was processed to derive land surface temperature maps and land cover classification maps for Enugu City and its peri-urban fringe, using the split-window algorithm for temperature retrieval and supervised classification for land cover. Temperature-land cover correlations were computed across the urban gradient. Field air temperature measurements were taken simultaneously at fifteen stations representing different land cover types to validate satellite-derived surface temperature patterns. Results show that land surface temperatures in the central business district and dense residential zones average 6.2 degrees Celsius higher than forested peri-urban reference areas. Green cover declined by 18 percent across the city boundary between 2018 and 2023, primarily from conversion of residential garden vegetation to paved surfaces and building footprints. Industrial zones record the highest surface temperatures. Statistical analysis confirms a significant negative correlation between normalised difference vegetation index values and land surface temperature across all land cover categories. The heat island intensity is greatest during the harmattan dry season. The study recommends a mandatory urban tree planting policy and restrictions on removal of mature trees within the city boundary. Keywords: urban heat island, green cover, land surface temperature, Enugu City, satellite imagery.