Christiansen, T. 1998. Sediment Deposition on a Tidal Salt Marsh. Ph.D Dissertation, University of Virginia, Charlottesville VA pp. 134. Keywords:sedimentation, flow, suspended sediment, deposition, low marsh:: Abstract:The physical processes that control mineral sediment deposition on a mesotidal salt marsh surface on the Atlantic Coast of Virginia have been characterized through a series of measurements of sediment concentration, flow velocity, water surface elevation and local rates of deposition on the marsh surface. Flow and sediment transport have been characterized both temporally and spatially as a function of distance from the bordering tidal creek. Measurements were made at tidal conditions ranging from tides barely flooding the marsh surface to spring tides and storm surges. Flow velocities on the marsh surface are extremely low (\< 1cm/s) during all tidal conditions measured. Flow direction on the marsh surface is perpendicular to the flow in the main tidal channel, flowing onto the marsh surface on the rising tide and off the marsh surface on the falling tide. The marsh surface vegetation, {\it Spartina alterniflora}, has a significant dampening effect on the turbulence of the flow, promoting deposition of suspended particles. Shear stresses within the {\it Spartina alterniflora} canopy are insufficient to mobilize sediment from the marsh surface. Sediment concentrations at the marsh edge are higher on the rising tide than on the falling tide, and combined with a flow directed from the tidal creek towards the marsh interior or during a tidal cycle, this pattern indicates sediment deposition on the rising tide. Sediment concentrations at the edge of the marsh increase with increased tidal amplitude, whereas in the marsh interior sediment concentration remained low regardless of tidal amplitude. The concentration gradient between creek bank and marsh interior indicates that more sediment is deposited on the creek bank as tidal amplitude increases. Correlation of high sediment transport events with meteorological conditions indicate that all high transport events are associated with strong northeasterly winds. Based on these measurements, it is estimated that 27% of sediment deposited on the marsh surface is contributed by storms\; the rest is deposited during normal high spring tides. :: Notes: submitted by pwiberg, Wed Jul 8 11:46:35 EDT 1998 ::