Hydrodynamics and sedimentation in salt marshes: examples from a macrotidal marsh, Bay of Fundy

This paper presents an overview of sedimentary processes operating at the time scale of the individual tidal cycle in tidal creeks and on the marsh surface, with examples of data from an ongoing study of a high-macrotidal salt marsh in the Cumberland Basin, Bay of Fundy, Canada. nd suspended sediment concentrations were measured with electromagnetic current meters and OBS™ probes at stations set-up in the tidal creek system and on the marsh surface. Measured flow velocities in the tidal creek channels and over the marsh surface are generally low (<0.2 m s−1), reflecting the relatively short, straight creek geometry and absence of levees along the creek channels. At spring high tide, flow vectors are initially controlled by creek geometry and the topography of the marsh surface, but near high tide, when water depth over the marsh exceeds 1 m, flow vectors are controlled more by the general circulation in the Cumberland Basin and by the effects of winds and waves. Suspended sediment concentrations are in the order of 150–250 mg l−1 and are similar in the tidal creeks and over the marsh surface. Suspended sediment concentrations generally decrease over the tidal cycle but show little fluctuation in response to changing hydrodynamic conditions. Deposition on the marsh surface is highest in the low marsh area, except near the marsh cliff margin, and shows a significant positive correlation with distance from the marsh edge.