Hydrodynamics and associated sediment transport over coastal wetlands in Quanzhou Bay, China

Abstract

Coastal salt marshes represent an important coastal wetland system. In order to understand the differences between boundary layer parameters of vegetated and unvegetated areas as well as the mechanisms of sediment transport, several electromagnetic current meters (AEM HR, products of Alec Electronics Co. Ltd.) were deployed in coastal wetlands in Quanzhou Bay, China, to measure current velocity. During the low tide phase, the surficial sediment was collected at 10 m intervals. In situ measurements show that the current velocities on the bare flat were much higher than those in the Spartina alterniflora marsh. Current velocity also varied with distance from marsh edge and plant canopy height and diameter. Around 63% of the velocity profiles in the tidal creek can be described by a logarithmic equation. Over the bare flat and Spartina alterniflora marsh, a logarithmic profile almost occurs during the flood tide phase. Sediment analysis shows that mean grain size was 6.7 Φ along the marsh edge, and surface sediments were transported from bare flat to marsh; the tidal creeks may change this sediment transport pattern. The hydrodynamics at early flood tide and late ebb tide phases determined the net transport direction within the study area.