Gully erosion poses a significant environmental threat in southeastern Nigeria, with severe impacts observed in the Idemili Drainage Area, including ecological degradation, infrastructure damage, agricultural land loss, and community displacement. This study examines the spatiotemporal dynamics of land use and land cover (LULC) changes in relation to gully expansion, aiming to quantify their interconnections, identify erosion-prone locations, evaluate causative factors, and guide sustainable land management strategies. Landsat satellite imagery from 1992, 2002, 2013, and 2025 was processed using Google Earth Engine (GEE) with the Random Forest algorithm and analyzed spatially in ArcGIS 10.8. Image preprocessing included geometric, radiometric, and atmospheric corrections to ensure accuracy. The classification employed Anderson’s (1976) system, categorizing the land into barren land, built-up areas, farmland, forest, shrubs, and water bodies. The analysis identified trends, magnitudes, and rates of land cover transformations. The results indicated a dramatic increase in built-up areas, rising nearly sixfold from 6.01% in 1992 to 41.75% in 2025, while farmland and forest cover significantly decreased by 49.23% and 35.30%, respectively. Between 2013 and 2025, built-up areas expanded rapidly by 114.76%, coinciding with consistent reductions in farmland, forests, and shrublands. Additionally, the increase in water bodies suggests altered drainage patterns contributing to gully formation. The substantial growth of built-up areas and reduction in protective vegetation cover are identified as primary landscape changes exacerbating runoff and soil instability, thereby intensifying the susceptibility to gully erosion. These findings demonstrate a critical relationship between LULC changes and environmental degradation, emphasizing the urgent need for effective land management and targeted erosion mitigation measures in the Idemili Drainage Area.