Dams are one of the most important fundamental structures all around the world. Given the high volume of water in the dams, they are susceptible to damage and destruction, leading to large financial losses and fatality. Therefore, by installation of instrumentation data in the dam’s body and execution of terrestrial surveying network, stability and safety of dams can be monitored. However, occasionally abnormal processes take place in the dam’s body and foundation that do not match with the instrumentation data’s outcomes. In the recent years, with the evolution and progress of radar imaging techniques and the image processing approaches, large deformations in the dams’ and bridges’ body can be monitored precisely. In the current study, the abnormal deformation and displacement taken place within the time period of Sentinel-1A 2014-2018 on the downstream part of Taleqan dam’s body were evaluated 4 mm/y and were compared with instrumentation data. The results imply that the occurred displacement is related to the external and protective layer of the dam’s body (Riprap) and has no correlation with the dam’s body behaviour.