momentum transfer caused by collisions between grains in a debris flow leads to excess pore water pressure, which reduces the shear resistance of the debris flow and results in very high mobility [14]. Thus, a debris flow can produce a peak discharge dozens of times higher than that of a flood in the same watershed [15; 16], and its flow characteristics may vary depending on the relative contents of water and sediment as well as the size and type of particles [3]. Therefore, it is necessary to identify the flow and deposition characteristics of debris flows and establish mitigation measures to predict and reduce the damage they cause. Debris flow mitigation measures can be mainly divided into structural and non-structural measures. Structural mitigation measures directly reduce debris flow damage using structures installed in the path of a debris flow; erosion control dams, flexible debris flow barriers, and berms can all be considered appropriate structures for this purpose. Non-structural mitigation measures indirectly limit debris flow damage using methods such as debris flow forecasting and warning systems or land use regulations. Figure 1 shows examples of real world slopes with multiple berms. This study evaluated the use of a berm, a structural debris flow mitigation measure consisting of a small step installed on a slope that effectively disperses rainwater, reduces the momentum of debris flows, and reduces the riverbed erosion. Berms can be easily constructed at a low cost compared to other debris flow mitigation measures. Therefore, several studies applying berms as a debris flow mitigation measure have been recently conducted. [PERSON] [17] introduced a method of applying berms to lateral, deflection, and terminal walls serving as open debris flow control structures, and suggested major considerations for structural design. [PERSON] et al. [18] pointed out that existing analysis methods for debris basins and deflection berms were not sufficient for the prediction of debris flow volume or the subsequent design of the berm geometry, impact load, and outlet, and accordingly suggested solutions and guidelines. [PERSON] and [PERSON] [19] performed numerical simulations by applying the finite difference method based on the mass conservation and momentum conservation equations to evaluate the behavior and mechanism of debris flow in response to the installation of berms on a slope. [PERSON] et al. [20] calculated the axial force, horizontal displacement, and safety factor using the finite element method to identify the stability of a slope according to the soil cohesion, the angle of internal friction, and the width and height of the berm installed upon it. To effectively design debris flow mitigation measures, it is necessary to first calculate the main debris flow parameters, such as the potential debris volume, impact force, flow velocity, peak discharge, mobility ratio, runout distance, and total travel distance [16; 21]. In particular, the flow velocity must be considered in the design of any debris flow mitigation measure because it directly influences the impact force and deposition characteristics, and is affected by the channel topography [3; 15; 22; 23]. In the countries where studies on debris flow characteristics have been actively conducted, the debris flow process and impact force can be estimated relatively accurately [10; 21; 24]. Domestic studies on debris flows in South  
Figure 1: Examples of using berms in real world slopes: (**a**) Slopes with berms in coal mine areas ([PERSON]/Shutterstock.com); (**b**) slopes with berms in Peru (lialina/Shutterstock.com). Korea, however, have been limited to trend analyses for simple experimental conditions. Numerical analysis, field observations, and flume experiments have all been previously used for research into the behavior and mechanism of debris flows.