Modeling urban expansions and its environmental effects in Arba Minch City, Southern Ethiopia using GIS, remote sensing, and Shannon entropy

Rapid urban expansion in developing countries has intensified land use and land cover (LULC) changes, resulting in significant environmental impacts that challenge sustainable urban development. Although Arba Minch City is one of the fastest-growing urban centers in southern Ethiopia, comprehensive studies integrating advanced geospatial techniques and quantitative models to assess urban expansion patterns and their environmental implications remain limited. This study analyzed urban expansion in Arba Minch, southern Ethiopia, between 2013 and 2023 using Geographic Information Systems (GIS), remote sensing, and the Shannon entropy model. The supervised classification, utilizing the maximum likelihood algorithm on Landsat 8 OLI/TIRS imagery, achieved high overall accuracies of 93% in 2013 and 94% in 2023. Additionally, Kappa coefficients of 0.91 for both years indicate a strong level of classification reliability. LULC change analysis revealed a notable increase in built-up areas by 1262.34 hectares, primarily at the expense of vegetation (-929.34 ha) and bare land (-359.19 ha). During 2013–2023, vegetation indices (NDVI) declined from an average of 0.31 to 0.2, while built-up index (NDBI) values increased from a mean of -0.17 to -0.09. Land Surface Temperature (LST) rose from 18.7 °C - 35.6 °C in 2013 to 19.6 °C - 44.0 °C in 2023, reflecting intensification of the urban heat island effect. The Shannon entropy analysis indicates dispersed patterns of urban growth, particularly toward the northwest (NW) and northeast (NE) directions. Furthermore, the urban expansion intensity index (UEII) uncovered a high level of urban growth intensity (UEII=1.64). The findings indicate substantial spatio-temporal changes in LULC and urban growth during 2013–2023. The study concludes that rapid and dispersed urban growth in Arba Minch City has led to considerable environmental degradation. It recommends the implementation of sustainable urban planning strategies, protection of remaining vegetation, and integration of geospatial tools into urban management policies to balance future urban development with environmental conservation.