Near-bed currents and suspended sediment transport in saltmarsh canopies

A field study was undertaken to measure near-bed current velocity, water le vel and suspended sediment concentration on unvegetated mudflat, and in rec ently developed Scirpus mariquete and Spartina alterniflora canopies in the Changjiang Estuary, China. Near-bed current (a combination of both tidal c urrents and wave motion) velocities were up to 50 cm s(-1) in saltmarsh can opies and on the mudflat. Near-bed current velocity within a saltmarsh cano py 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 wa s reduced by 16% within the estuarine saltmarsh canopy compared to open mud flat. Reductions in near-bed current velocities within the saltmarsh canopy were larger during ebb tide than flood tide. Suspended sediment concentrat ions were found to be lower within the estuarine saltmarsh canopies compare d to the unvegetated mudflat.