RFID-Aided Sediment Transport Monitoring—Laboratory and Preliminary Field Test Results

Although often disregarded during natural hazard evaluation, sediment transport phenomena could represent a matter of major significance when dealing with hydro-geological instabilities with possible adverse impacts on river basin management, structural integrity of hydraulic structures, and public safety. Under conditions of high precipitation and consequent propagation of flood waves, the phenomenon is severely intensified, especially in Alpine and pre-Alpine areas, characterized by relatively high slopes and intense sediment supply from the upstream valleys. This study investigates the application of RFID (Radio-Frequency IDentification) transponders (also referred to as tags) as a qualitative and quantitative sediment transport monitoring tool. Preliminary laboratory and field tests have been carried out on both transponders and transponder-equipped pebbles under various conditions of the surrounding environment such as burial and water depth in order to evaluate the performance of the technology. Results of the laboratory experiments indicate that the detection distance depends on the orientation of the tag itself and therefore insertion of two or even 3 tags in a single pebble according to its axes is necessary in order to ensure higher recovery rates. Further, characteristic grain size curves have been used to identify 90 RFID-equipped and painted grains divided in several size classes and used in a first field experiment. The groups have been deployed at predefined locations characterized by similar granulometry and flow conditions. Two recovery campaigns have been since carried out, with the former some 15 h after a relatively intensified rainfall event and the latter two days later. A relatively high recovery rate has been recorded (72% during the first and 78% during the second campaign) to a distance of up to 50 m downstream of the initial deployment point. Despite some limitations, the technology appears to yield promising insights in the more detailed understanding of sediment transport.