Detection and Velocimetry of Floating Wood-debris for Flood Disaster Risk Management using Electromagnetic Imaging

River wood-debris are a major hazard to lives and infrastructures, because tons of wood material can travel nearing the speed of the flood-flow. If post-event mapping, detection and numerical simulation have made important progress, it is still impossible to detect the wood-debris as they travel, due to poor visibility conditions (rain, night…). The present work aims to solve this issue by adapting Ground Penetrating Radar as an electromagnetic imaging method for in-flow wood debris detection. Laboratory test over a water circulation flume using a 800 MHz nominal frequency antenna sampling at 100 Hz a set of single wood logs of 20 cm length has shown that the method had the potential to detect moving wood debris, and that it could “see” underneath to the flume floor. The experiments resulted in the ability to count wood debris travelling underneath the antenna, and instantaneous velocity were obtained with velocities ranging from 0.307 to 0.352 m/s, which slightly higher than the averaged velocity measured from video, due to the acceleration time when wood was introduced in the flume.