Using Smart Sensors to Track Woody Debris in Flume Experiments

When triggered by floods, large wood travels downstream accumulating around river structures that may cause structural damage and eventually collapse. The use of sensors embedded within the woody debris has been recently employed in the study of debris transport in river catchments. However, their application for woody debris has not been fully explored yet and their validation is at an early stage. In this framework, laboratory experiments are designed to track the movement of a woody dowel along a tilting flume by using a smart sensor. The woody dowel is 200 mm long and has a diameter of 35 mm. It has a cylindrical borehole with a diameter of 25 mm along its whole length. A sensor tag is placed within the borehole to detect the movements of the woody dowel. The experiments consist of releasing the woody dowel into the flume tank and tracking its movements for different flow conditions. Experiments are recorded by two cameras capturing woody dowel movements from the top. By coupling the sensor outputs and the video recordings, it is possible to compute positions, velocity, acceleration and angular velocity of the woody dowel. Results show that the sensor embedded in the woody dowel can detect minor changes in the flow field. A smoothed particle hydrodynamics (SPH) model has been used to simulate the experiments. The comparison of laboratory and numerical data has allowed the refinement of numerical modelling of woody debris transport which ultimately contributes to better assessment of the hazard it poses.