Bedload tracing with RFID tags in gravel-bed rivers: Review and meta-analysis after 20?years of field and laboratory experiments

Soon after their first deployment in rivers in the early 2000s, RFID tags rapidly became the reference technology for bedload tracing in rivers. We can estimate from the literature that during the last 20 years, more than 30,000 RFID tracers have been injected in gravel-bed rivers all around the world to study bedload transport. Many field experiments have been reported in a great diversity of fluvial environments, complemented by many laboratory experiments and methodological developments. This paper proposes a review of these works, notably based on the compilation of more than 350 RFID surveys, complemented by 97 magnetic surveys, for a total of 125 study sites. The meta-analysis of this database shows that RFID tracers have improved our understanding of sediment transport in fluvial environments with rapid bedload dispersion. It is also shown that central positions of tracer plumes are moving faster over time than tracer leading fronts, as attested by a general relation between maximum and mean distances of transport. The most recent methodological developments based on the use of active UHF RFID tags show that it is now possible to conduct efficient bedload tracing experiments not only in small streams, but also in large gravel-bed rivers or very active braided channels. Other addressed topics include RFID deployment and survey in river channels, controlling factors of tracer mobility (flow conditions, grain-size and shape, channel morphology), bedload monitoring approaches using RFID tracers, and applications of RFID tracers for evaluating human effects on bedload transport. Key challenges of bedload tracing with RFID tags are also proposed. A review of field and laboratory radio frequency identification (RFID) bedload tracing experiments is proposed, including a meta-analysis of data coming from 459 tracer surveys for a total of 125 study sites. RFID tracers open new avenues for exploring fluvial environments prone to rapid bedload dispersion. The most recent methodological developments based on active ultra-high frequency RFID tags show that it is now possible to conduct efficient bedload tracing experiments not only in small streams but also in large gravel-bed rivers or active braided channels.image