Our study aims at determining values of the pressure in the vicinity of a structure subjected to a debris flow impact, and their evolution in time and space, for a given incident flow. We used a numerical model based upon the SPH (smoothed particles hydrodynamics) numerical method and simulated the flow features upstream of an obstacle impacted by a viscoplastic fluid wave. We focus interest on the pressures developed on the structure during the impact. The results are analyzed in view of the incident flow features, characterized by its Froude number Fr. We evidence a transition between what we name the dead-zone impact regime and the jet impact regime. We establish that this transition occurs for values of the Froude number between Fr ≈ 1.3 and 1.5. We evidence the respective roles of the gravitational and kinetic components of the pressure. Finally, we study the spatial distribution of the pressure applied to the obstacle and its evolution with time depending on the impact regime.