Remote sensing analysis of urban heat island dynamics in Bahir Dar and Hawassa, Ethiopia: The role of vegetation, urbanization, and climate

Abstract

The rapid urbanization within most developing nations has resulted in the Urban Heat Island (UHI) effect. Yet, there is a lack of substantial research on local environmental and climatic variables that define the UHI intensity. This study investigated the relationship between urbanization, vegetation dynamics, and UHI intensity in Bahir Dar and Hawassa, Ethiopia, from 2000 to 2022, using Landsat 7, Landsat 8, and climatic variables such as temperature, humidity, wind speed, and rainfall. The analysis was computed with Python and ArcMap. Accordingly, the results demonstrated a slight reduction in Land Surface Temperature (LST) for both cities, with variation in Bahir Dar at (R² = 0.50) compared to Hawassa at (R² = 0.07), showing other factors controlling the temperature in Hawassa. Indeed, Bahir Dar in the Ethiopian Highlands exhibits higher temperatures than Hawassa in the Rift Valley. Changes in the Normalized Built-up Index (NDBI) have recorded weak negative trends, (R² = 0.20) for both cities, which means the expansion of the built-up areas is inconsistent. While the increase of Normalized Difference Vegetation Index (NDVI) in Bahir Dar was significant (p < 0.01), that of Hawassa was not significant (p = 0.107). UHII in Bahir Dar has significantly declined, with (R² = 0.68; p < 0.01) while in Hawassa UHII characterizes variations with a downward trend (R² =0.42; p < 0.01) including even negative values recording, indicating cooler urban than the surroundings. This calls for deep attention to local specificities for any climate adaptation strategy. Further studies should be conducted with multisource remote sensing, socioeconomic factors, and predictive modeling to strengthen evidence-based urban planning and decision-making.