|The authors developed the methodology for monitoring the stream flow on the active live bed condition using a RADAR on a drone. In this study, the authors applied it in order to monitor flow through levee breach, whose breaching change over time. The RADAR is the one which was developed and tested as fixed type by the authors using the Frequency Modulated Continuous Wave radar techniques. One of the next applications of this kind is mounting it on the drone to widen the capability of the measurement. With mounting the RADAR as well as the video camera on the drone, velocities, water surface elevation, length of surface wave were measured at when levee breach occurs. One of the challenges was estimation of water depth, which changes as time goes as levee breach progress. With combining the information obtained by the drone and knowledges from sediment hydraulics, the authors estimate the water depth and determine the flow rate.