Granular flows pose significant threat to structures and infrastructures, which can act as obstacles to flow propagation, potentially leading to severe damage or even structural collapse with considerable social and economic losses. Accurate assessment of these phenomena requires reliable predictions of both the impact forces transmitted to structures and the deformation of the granular mass, including the maximum run-up height and the final deposit geometry. The Discrete Element Method (DEM) is particularly well suited for investigating the dynamic interaction between dry granular flows and obstacles. It naturally captures highly dynamic processes and large displacements, while requiring calibration of a limited number of interaction parameters. Moreover, DEM can reproduce the transition of granular material behaviour from fluid-like to solid-like as impact kinetic energy is progressively dissipated. In this study, DEM is employed to simulate the impact of dry granular flows against rigid obstacles in both plane strain and three-dimensional configurations, representative of a wide range of practical scenarios. The numerical results are analysed to investigate the influence of impact geometry on impact forces and granular mass deformation, providing insights for improved risk assessment and the design of protective structures.