The Eastern Solent Coastal Partnership was awarded £4,000 contribution from SCOPAC [clickable link to website] (Standing Conference on Problems Associated with the Coastline) to develop the techniques used for tracking gravel sized beaches, using RFID technology.
A series of simple tests were carried out to assess the detection range of the various sizes of RFID tag, at different orientations to the reading antennas and varying depths within the sediment. Pebbles were tested for depth range both within the upper gravel beach and on the upper foreshore area which was predominately a mixed sandy gravel.
Test pebbles containing tags of the size 23 mm and 12 mm were placed on the beach at varying depths below the beach surface. The pebbles were placed at interval depths of between 50-100 mm, until they were no longer detectable by the RFID antennas.
Figure 1 and 2 show an example of the interval depths used for the burial depth trials at Lee-on-the-Solent.
Results suggest that the larger RFID tag (23mm) has a greater detection range than the smaller 12mm tag. The detection range is greatest in the gravel for both pebble sizes, although the smaller tags are unlikely to be detected in sediment depths of greater than 30-35cm. Orientation seems to be less important in the smaller pebbles, whilst a vertical orientation of the 23mm tag improves the detection range.
Full details of this study, including the results from the retrieval surveys can be found in this report