First feedbacks on a new method using active transponders (a-UHF tags) for tracking pebbles in rivers
Abstract
In the last decade, low frequency (134.2 kHz) passive integrated transponders (PIT-tags) have become widespread and popular technique for tracking pebbles. It is used for the locating individual particles after flow events, estimating critical discharge and critical shear stress above which tagged particles are entrained. However, the low tracer recovery rates when deployed in active bedload transport conditions or large rivers, present a significant drawback (Table 2 in Chapuis et al., 2015). These are mainly due to detection range of in-field maneuverable RFID reading systems (typically < 1m; Chapuis et al., 2014; Arnaud et al., 2015; Cassel et al., 2016) leading to long, exhausting and not systematically successful surveys. In order to increase tracer recovery rates and reduce in-field time prospection, we developed new coarse sediment tracers combining synthetic pebbles equipped with Ultra High Frequency active transponders (a-UHF tags). We characterized distances of detection in water and saturated sediment layer and proposed in-field protocol to determine tracer position with good accuracy (Cassel et al., 2017). First deployments of these tracers have been done in two rivers reaches characterized by challenging conditions: the Miribel Canal, a channelized stream with significant water depths (< 2.5 m) and alternated gravel bars and the Buëch river within a braided reach exhibiting large areas of emerged gravel bars. First surveys, conducted in 2017, show very encouraging results: rates are beyond 70%, mean and maximum distances of travel are of 323 and 1060 and of 982 and 3240 meters respectively for Miribel Canal and Le Buëch, obtained from very short in-field prospection time (< 8 day/operator per site). These first results confirm the interest of this new method for in-river pebble tracking. New methods of prospection are currently tested and articulated to optimize in-field prospection efforts according to study purpose, from sediment transfer continuity (only downstream distance needed) to macro form dynamics (2D accuracy needed). Arnaud F, Piégay H, Vaudor L, Bultingaire L, Fantino G. 2015. Technical specifications of low-frequency radio identification bedload tracking from field experiments: Differences in antennas, tags and operators. Geomorphology 238 : 37-46. DOI: 10.1016/j.geomorph.2015.02.029 Cassel M, Dépret T, Piégay H. 2017. Assessment of a new solution for tracking pebbles in rivers based on active RFID. Earth Surface Processes and Landforms 42 : 1938-1951. DOI: 10.1002/esp.4152 Cassel M, Piégay H, Lavé J. 2016. Effects of transport and insertion of radio frequency identification (RFID) transponders on resistance and shape of natural and synthetic pebbles: applications for riverine and coastal bedload tracking. Earth Surface Processes and Landforms DOI: 10.1002/esp.3989 Chapuis M, Bright CJ, Hufnagel J, MacVicar B. 2014. Detection ranges and uncertainty of passive Radio Frequency Identification (RFID) transponders for sediment tracking in gravel rivers and coastal environments. Earth Surface Processes and Landforms 39 : 2109-2120. DOI: 10.1002/esp.3620 Chapuis M, Dufour S, Provansal M, Couvert B, de Linares M. 2015. Coupling channel evolution monitoring and RFID tracking in a large, wandering, gravel-bed river: Insights into sediment routing on geomorphic continuity through a riffle-pool sequence. Geomorphology 231 : 258-269. DOI: 10.1016/j.geomorph.2014.12.013
- Publication:
-
EGU General Assembly Conference Abstracts
- Pub Date:
- April 2018
- Bibcode:
- 2018EGUGA..20.4643C