The assessment of soil erosion rate and its spatial distribution in the hilly-mountainous Nisava River basin was conducted by Universal Soil Loss Equation (USLE) model through a GIS-based approach. A Landsat 7 Enhanced Thematic Mapper (ETM+) image and normalized difference vegetation index (NDVI) were used for the determination of crop management factor.
The average annual soil loss was estimated at 13.1 t·ha^-1·yr^-1, classifying the Nisava River basin under the high erosion rate category. About 44.1% of the watershed area was characterized by slight erosion rate (< 5 t·ha^-1·yr^-1), 15.5% of the area was found to be under moderate erosion rate (5-10 t·ha^-1), 18.9% of the area was under high erosion rate (10-20 t·ha^-1), while around 14.4% of the area was under a very high erosion rate (20-40 t·ha^-1·yr^-1). Severe erosion rates (40-80 t·ha^-1·yr^-1) were observed at 5.9% of the study area (168 km²), whereas very severe erosion rate (>80 t·ha^-1·yr^-1) described about 1.3% of the watershed (35.9 km²). The highest erosion was found on a sloppy terrain with agricultural activity. The results of this work are in agreement with previous studies conducted in the watershed, which indicates the presented methodology could be applied with eventual further improvements for the evaluation of erosion factors on soil resources in Serbia when limited data are available.