The use of baffle arrays behind a rigid barrier is an effective method to reduce impact force by dissipating flow energy with filtering boulders from debris flows. To prevent structural damage of the rigid barrier, appropriate configurations of the baffle arrays are needed; however, design guidelines for the geometric construction of baffle arrays have not yet been proposed. One of the major challenges in designing multiple structures (baffles and a rigid barrier, etc.) is to set up a framework for a safe and economical design. The flow–structure interaction and impact force of debris flows on a rigid barrier are affected by the configuration of baffles installed behind the rigid barrier. In this study, to evaluate the flow behavior and the dynamic impact force on the terminal barrier after the flow has passed through the baffle arrays, we conducted a series of small-scale flume tests under various baffle heights and a number of rows. The test results revealed that the installation of baffles reduced the run-up height and the impact force on the terminal rigid barrier. The flow impedance induced by baffles had a significant influence on the dissipation of the kinetic energy of debris flows. Moreover, additional baffle rows produced a greater reduction in the run-up and impact force by decreasing debris flow and boulder mobility.