Near-bed currents and suspended sediment transport in saltmarsh canopies

A field study was undertaken to measure near-bed current velocity, water level and suspended sediment concentration on unvegetated mudflat, and in recently developed Scirpus mariquete and Spartina alterniflora canopies in the Changjiang Estuary, China. Near-bed current (a combination of both tidal currents and wave motion) velocities were up to 50 cm s(-1) in saltmarsh canopies and on the mudflat. Near-bed current velocity within a saltmarsh canopy was generally less than that on the mudflat, regardless of the phase of the tides or the tidal current direction. Mean near-bed current velocity was reduced by 16% within the estuarine saltmarsh canopy compared to open mudflat. Reductions in near-bed current velocities within the saltmarsh canopy were larger during ebb tide than flood tide. Suspended sediment concentrations were found to be lower within the estuarine saltmarsh canopies compared to the unvegetated mudflat.