Integrated video-sediment tracer technique for sand transport measurements

Abstract

Experiments on beach profile evolution and related sediment transport were carried out at LNEC’s large wave flume. An eighteen-minute long record of an erosive wave condition impacting on sandy beach profile was video-monitored through a camera device looking at the wave flume lateral window. This included conceiving a sand-tracing procedure, which required setting a procedure to obtain a sand tracer with similar size and hydraulics properties as the native sand, and developing a video-image analysis technique capable of detecting and measuring dyed-sand areas on the video-frames, as well as tracking and calculating centre of mass displacement throughout the selected frame sequence. Preliminary results of the velocities of the dyed-sand centre of mass position along one record are shown and discussed. This technique allows obtaining intra-wave information of the sediment transport at the location of the video-records, complementing the time-integrated information gathered from bed profiling.