Hydraulic Characteristics and Similarity of Debris Flows under the Erodible Bed Experiments

Flume experiments have been widely used in many studies to investigate various characteristics of debris flows. However, some researchers have raised concerns about the adequacy of these experiments in simulating natural debris flows, as the majority do not account for entrainment and similarity. This study aimed to replicate debris flows that are dynamically similar to natural debris flows through flume experiments incorporating entrainment, and to analyze their flow characteristics. A 3.2-meter-long erodible bed composed of gravel was installed in the flume, and debris flows were generated by continuously supplying water at a constant discharge. The flow characteristics, including flow depth, flow velocity, and volumetric sediment concentration, were measured under varying flume slopes and water discharge conditions. The results showed that flow depth and volumetric sediment concentration exhibited an upward trend with increasing flume slope gradient under constant discharge conditions. Conversely, flow velocity exhibited a tendency to increase with higher discharge under the same slope conditions. The dynamic similarity of the flume experiments was evaluated using various dimensionless parameters, including the Froude number and the Bagnold number. These evaluations indicated that the flume experiments closely replicated the stony-type debris flows observed in nature.