<p>River Morphological variation channels are serious pointers of watershed sustainability and dynamics because they inspiration flood risks,, aquatic habitat stability, sediment transport and infrastructure vulnerability. This investigation evaluates the long-term morphological progress of the upstream Abay River (Blue Nile basin, Ethiopia) between 1978 and 2021 using Geographic Information System (GIS) techniques and multi-temporal Landsat MSS, TM, and OLI imagery. Channel width and area were measured at four fixed cross-sections to epitomize longitudinal variability. Results display a strong rise in channel area from 16.26  in 1978 to 19.08 Km² in 2021, corresponding to a 16.62% net expansion. Width trends varied spatially: upstream reaches narrowed (–17.47% at point A) while downstream reaches widened substantially (+ 63.58% at point D). These patterns are consistent with known fluvial alteration processes including sediment redistribution, channel deepening and lateral bank erosion documented in similar systems using remote sensing methodologies (Vistula River, Poland; Tana River, Kenya). The evolution fills a main research gap by quantitatively evaluating multi-decadal morphological change in the upstream Abay River. A river system where direct field measurements are rare but where scheduling decisions depend on an considerate of geomorphic dynamics. The results offer a reference point for highlight the value of remote sensing/GIS in monitoring environmental change in data-limited basins and sustainable river corridor management.</p>