Alluvial river systems alter their geometry over time due to human-induced or natural factors acting on the catchment, in the river corridor, and in the river bed. The upper Blue Nile basin's alluvial river channels have been impacted by both natural and humancaused factors. The purpose of this study is to investigate the channel planform changes along the 37-km section of the Abay River in the upper Blue Nile basin (Ethiopia) from Chara Chara weir to Tis Issat Fall. Using ERDAS 2015 and ArcGIS 10.4 tools, channel planform information was extracted from topographic map, satellite images and Google Earth images for these nearly 37 years’ period. Bed aggradation was observed in the river, according to field observations. The results indicate that the Abay River from Chara Chara weir to Tis Issat Fall has undergone major planform changes. The average channel width decreased by 60 % from 283.06 m to 112.5 m on average from 1984 to 2020. The mean braiding index increased by 105% from 1.16 to 2.38 and decreased by 26 % from 2.38 to 1.76 on average from 1984 to 2011 and 2011 to 2020, respectively. The sinuosity of the plan form changed very little from 1.36 to 1.39. Effect of relatively minor fluctuations in some climate features over time scales of a few decades can resulted in significant changes to the fluvial system through changes in the flood regime, sediment regimes, and vegetation along the riparian zone. The effects of land use change have provided sediment to the channel. The effect of flow regulation significantly decreased the natural stream flow, decreased sediment transport capacity of out -flowing discharge of the channel and have contributed to the huge sedimentation in the river bed and was changed to bars. This bar trapped suspended sediment which facilitated the growth of vegetation. Where the impact of vegetation on the river bed and banks have prevented erosion of the bank and bars and screening it promoted deposition. In general, this study demonstrated that there are significant modifications to the planform at the floodplain, riverbank, and riverbed level. The Abay River's future channel should be monitored for vegetation encroachment, basin activity, and flow regulation. Keywords: Planform change; Chemble River; Chara Chara weir; ERDAS; GIS, Abay River.