Hydraulic structures such as dams have inevitable effects on their downstream that requires investigation. This study assesses the impacts of hydraulic structures on river morphology in Selamko watershed, Lake Tana basin, Ethiopia. Objectives of this thesis were to assess the morphological metrics river bank shift extracted from Satelite images, to assess Selamko river plan form changes and to investigate vertical change of Selamko River downstream from the dam and HEC-RAS model was used to assess the river bed changes cause of released suspended sediment to the downstream part of selamko River. To compare the vertical adjustment of the Selamko River, current river cross-sections were taken at different intervals and the past cross-sections were developed from the old topographic map of the study area. For the data preparation and analysis map processing Arc GIS 10.4.1 were used. From the analysis of vertical change selamko river reaches are characterized deggrading by hydraulic structure with an average deggrading value of 0.78 m,0.92m and 0.56m and 0.35 for the period 2005and 2019 respectively. From the Satelite images of the year 2005,2010 and 2019, the river center lines, banks and width of the river were digitized and sinuosity index were calculated to assess the planform chnges. The change in sinuosity value is insignificant for the year 2005 (1.427), 2010 (1.299) and 2019(1.291). The result shows that Sinuosity Index decreases, it indicates that the straight activity of the river decreases, thus contributing less sediment into the river and to save precious land from been eroded all along the river course. The main channel width to derive the past channel width from historical satellite images and The Google Earth satellite images of the year 2005 and 2019 shows gradual narrowing in the downstream direction. This may be due to decreasing erodibility bank materials, to overlay analysis of Selamko River of the three years 2005, 2010, and 2019, it was clear that the maximum bank shift of 85.96% narrowed and 14.04% widened has occurred.