COMBINING RFID AND MOTION TRACERS WITH STATIONARY ANTENNAS TO MONITOR BEDLOAD TRANSPORT IN COARSE ALLUVIAL CHANNELS

Quantifying bedload characteristics in coarse alluvial streams is often challenging because transport occurs only during high discharge events. We employed traditional and developed new tracer methods in Reynolds Creek, Idaho. Reynolds Creek is a gauged, coarse alluvial stream that experiences both flash flooding as well as longer, weeks-spanning snowmelt floods. Study objectives include constraining: i) timing of bedload entrainment and disentrainment, ii) bedload displacement distances within and between events, iii) bedload velocities and iv) channel active layer thicknesses. Since 2011, we have deployed ~1500 Radio Frequency Identification (RFID) and ~170 motion tracers along with several stationary RFID antennas. RFID tracers consist of natural or concrete gravels and cobbles embedded with RFID tags while motion tracers are cobbles that include RFID tags as well as accelerometers. These accelerometers log x, y, z accelerations every 10-15 min and changes in accelerations indicate motion since previous record. Relocating tracers after transport events, we know total displacement distances and after a record flood, several tracers traveled over 6 km. Beyond before/after-flood positions, stationary antennas recording passing RFID and motion tracers provide us additional spatial information during floods. We synchronize stationary antenna and motion tracer records with discharge data to identify stream conditions when bedload motion occurs. These field techniques allow us to collect rare temporal and spatial bedload datasets in coarse alluvial channels.