Rigid barriers are commonly installed to mitigate debris flows in mountainous regions around the world. Debris flows impacting a rigid barrier have the tendency to run-up along its vertical face. Hence, it is important for engineers to be able to predict and assess the run-up height to prevent overspilling of debris. More importantly engineers must understand how structural countermeasures, namely baffles and deflectors, can control run-up. A 5 m-long rectangular flume model was adopted to examine the run-up mechanisms of single-phase flows against rigid barriers, and investigate the interaction mechanisms of both baffles and deflectors in suppressing run-up. High-speed imagery was used to estimate the flow velocity and thickness of the flow. Both granular and water flows were used, separately, to understand the mechanisms for the simplest flow cases of frictional flows and inviscid flows, respectively.