Hydrological alterations were happening globally because anthropogenic effects like land use changes by the conversion of lands to industrial areas, urbanization and agricultural lands. The main objective of this study was determining effect of land use land cover change on stream flow and sediment concentration on Gilgel Abay watershed. Historical land use land cover was generated using satellite images from USGS Earth Explorer data by supervised classification technique using maximum likelihood algorithm and the classified images were checked for classification accuracy and sediment data generated by sediment concentration equation based on discharge. SWAT2012 was used to generate stream flow and sediment concentration of Gilgel Abay river and the SWAT-CUP was used for calibration and validation. The land use land cover analysis result for three different years of 2000,2010and 2020 land use indicated were used for estimation of stream flow and sediment concentration. The sediment concentration data was generated using sediment rating curves of Gilgel Abay watershed. During the study period most parts of Cultivated land grass land changed into forest and shrub land. A decreased cultivated land and grassland by 15.48 % and 4.13% respectively, urban area, shrub land and forest rising by 12.13 %, 3.52% and 2.72% respectively. Over 20 years period (2000-2020) decreased of stream flow and sediment concentration by 2.53m 3 /s and 4.41mg/l respectively. The model results have showed a good agreement and correlation with the observed data with NSE > 0.5, R 2 > 0.6, and RSR < 0.08 values for this study used the daily data. The result of this study shows that land cover was change in to forest, shrub land and urban urea the base flow be coming decreased, because the eucalyptus plantation and irrigation practices increased, however the sediment concentration was decreasing because the forest and shrub land was increased from year to year. This helps decision-makers and stakeholders to plan and manage land and water resources more effectively. Keywords: land use land cover, sediment concentration., stream flow, Gilgel Abay watershed, SWAT and GIS