Science Serving Maryland's Coasts
William Nardin, Ph.D.
Horn Point Laboratory
Determining Flood-Ebb Dominance at an Artificial Salt Marsh on Poplar Island, MD
Salt marsh morphologies are commonly affected by strong tidal processes that regulate sediment accretion rates. Here, we investigate how the interplay between tides and wind affect sediment dynamics in a low energy salt marsh at the Paul S. Sarbanes Ecosystem Restoration Project at Poplar Island, an active restoration site where fine-grained material dredged from the upper Chesapeake Bay is being used to restore tidal marsh habitat. Tidal currents were measured over multiple tidal cycles in the inlet and tidal creeks of one marsh at Poplar Island, using Acoustic Doppler Current Profilers (ADCP) to estimate water flows and marsh connectivity. Sediment fluxes were determined by estimating suspended sediment concentrations (SSC) with ADCPs and validated against total suspended solids measurements taken on site. Channel morphology influences flood-ebb dominance in marshes, where deep, narrow channels promote high tidal velocities and incision, increasing SSC and reducing resilience. Multiple regression analysis identified a significant relationship between water flows, depth, and SSC at the culvert. Concerns about erosion and sediment export have been highlighted by our study, showing the highest fluxes in SSC coinciding with peak ebb tides. Understanding the drivers of salt marsh morphodynamics is vital for informing restoration practices and designs to improve resilience.
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