Spatiotemporal assessment of urban expansion and its impact on land surface temperature in Adama City, Ethiopia

Rapid urban expansion is among the most significant forms of land-use/land-cover (LULC) transformation and has important implications for urban thermal environments. This study assessed the spatiotemporal impact of urban growth on land surface temperature (LST) in Adama City, Ethiopia, over 36 years (1986, 1999, 2011, and 2022). Multi-temporal Landsat imagery was used to map LULC using maximum-likelihood supervised classification, retrieve LST from thermal bands, and analyze LST relationships with the Normalized Difference Vegetation Index (NDVI) and the Normalized Difference Built-up Index (NDBI). The maximum likelihood supervised classification results performed well with an overall accuracy of 92.8% and a kappa coefficient of 0.9 for 1986, and 95.2% with a kappa coefficient of 0.93 for 2022. The results showed substantial urban expansion, with built-up land increasing from 6.05 km 2 in 1986 to 53.6 km 2 in 2022, while cropland declined from 117.63 km 2 to 62.42 km 2 . Over the same period, the mean citywide LST increased from 29.53 °C to 32.14 °C. Regression analysis further showed that LST was negatively associated with NDVI and positively associated with NDBI, indicating that vegetation has a cooling effect, whereas impervious built-up surfaces intensify heating. The study provides an integrated, context-specific, validation-oriented, and planning-relevant LULC–LST application by combining long-term land-cover transition analysis, MODIS-supported LST validation, spectral-index interpretation, and spatial clustering assessment within a single diagnostic framework for a rapidly urbanizing Ethiopian secondary city. Overall, the findings demonstrate that urban growth has been a major driver of surface warming in Adama City. These results support the need for urban planning interventions that prioritize tree planting, protecting vegetated land, and expanding green infrastructure to reduce thermal stress and promote sustainable urban development.