Tracking the mean annual velocity and vertical mixing of bedload tracers

This research is part of a project to understand urban channel degradation and assess the benefits of stormwater management and channel restoration. Specific objectives are to i) describe the development and field testing of a new Radio Frequency Identification (RFID) tracer with a self-righting inner ball (a ‘Wobblestone’) and ii) describe the variability in the bedload transport over a set of five creeks with varying degrees of urbanization. The Wobblestone improves the recovery rate and precision of the tracing technique and allows the estimation of burial depth with only a minor error (~ 2 cm). The mean annual particle velocity (a ratio of the distance travelled per year to channel width) shows that urbanization accelerates the transport of coarse particles, but high velocities are also observed at relatively undisturbed sites. Sediment transport measurements remain snapshots of a process with high spatial and temporal variability at different timescales.