Large-Scale Experiment and Numerical Modeling of a Riverine Levee Breach

This study aims to clarify the mechanism of riverine levee breach and propose a new numerical model for that phenomenon. Large-scale experiments of overtopping breach were performed using an experimental flume located on the floodway of an actual river channel. By taking advantage of the scale of the flume, the levee breach process was monitored with state-of-the-art observation devices under highly precise hydraulic conditions. Four test cases were performed with variations of inflow rate, levee material, and levee shape, and the levee breach was monitored quantitatively using acceleration sensors installed in the levee body. From the results of the experiments, the breach process is categorized into four stages, focusing on the breach progress and hydraulic characteristics. It was determined that the correlation between the breached volume and the hydraulic quantities of velocity, water level, and Shields number can be expressed by an equation similar to that for bed load transport. Finally, a two-dimensional numerical model is proposed by integrating the experimental results into geomechanics, and a good reproduction result is obtained.