As a result of ongoing human induced or natural factors acting on river channels, banks, and within a catchment, alluvial river systems change their course and morphology over time. Rivers entering a static water body are affected by the base level changes and the backwater effects. For coastal rivers, the planform changes are highly pronounced at the fluvial deltas and flood plains. Aggradation, degradation, progradation, meandering, and formation of islands and distributary channels are common processes on coastal rivers. This study investigates planform changes and landscape responses of Gilgel Abay river about 36 km stretch starting from the bridge, near Chimba, to its entrance to Lake Tana by using historical images for the last 60 years (1957 to 2020) and field observation. The study reach was divided in to three. For data preparation and analysis, image analysis software's; ENVI, ERDAS IMAGINE, and ArcGIS were used. The overall results (sinuosity, width, and island) show that, Gilgel Abay river within the study reach has shown little change in its planform for the last 60 years. However, the alluvial delta formed at the mouth of the river has shown huge change; delta has expanded about 19.74 ha/year and prograded 9 m per year towards the lake and the river shifts about 1.73 km to the left. In general, for the planform changes that occurred in Gilgel Abay river channel and fluvial delta, human-induced factors have a great contribution. Increasing interest for new settlements inside delta flood plain, productive agricultural land and artificial lake level rise changes the river planform and the delta appearance. Quantitative and qualitative mapping of river and delta coupling with feeding basins and floodplains, is important to enhance and understand the socioeconomic influences on river morphology and needs an integrated management framework.