Sediment Exchange Between a Euhaline Salt Marsh in South Carolina and the Adjacent Tidal Creek

Abstract

The net inorganic suspended sediment (ISS) and organic suspended sediment (OSS) transport between a euhaline salt marsh and an adjacent tidal creek was studied on 34 tidal cycles between June 16, 1983 and June 19, 1984. A flume was used to measure the net sediment exchange during tidal inundation and a weir study characterized the export of this material from the marsh via runoff during low tide exposure (including storm events). Mean flood ISS and OSS concentrations varied from 6.0 to 68.4 mg 1^-1, respectively, with the highest values observed during the summer. The marsh was a sink for suspended sediments throughout the year with the largest imports observed during the summer months (especially after rain events). The annual flux estimates suggest there was an ISS and OSS import to the vegetated marsh during tidal inundation of 827 gm^-2 and 185 gm^-2, respectively. Export values of ISS and OSS from the marsh via runoff during low tide exposure (including rain events) were approximately 35% of the respective import values during tidal inundation. The net flux (flume + weir) of inorganic and organic sediments between the vegetated marsh and the adjacent tidal creek suggests the marsh was a sink for both constituents. The inorganic sediment input was close to that needed for the marsh surface to keep pace with the recent rise in sea level (1.5 - 4.0 mm y^-1). It is hypothesized that the marsh keeps pace with the rise in sea level by a dynamic interaction of depositional and resuspension processes that are controlled by differences in marsh and mean sea level height, sediment load, and climatic events.