Sediment dynamics of a divergent bay–marsh complex

Estuaries and Coasts
By:  and 



Bay–marsh systems, composed of an embayment surrounded by fringing marsh incised by tidal channels, are widely distributed coastal environments. External sediment availability, marsh-edge erosion, and sea-level rise acting on such bay–marsh complexes may drive diverse sediment-flux regimes. These factors reinforce the ephemeral and dynamic nature of fringing marshes: material released by marsh-edge erosion becomes part of a bay–marsh exchange that fuels the geomorphic evolution of the coupled system. The dynamics of this sediment exchange determine the balance among seaward export, deposition on the embayment seabed, flux into tidal channels, and import to the marsh platform. In this work, we investigate the sediment dynamics of a transgressive bay–marsh complex and link them to larger-scale considerations of its geomorphic trajectory. Grand Bay, Alabama/Mississippi, is a shallow microtidal embayment surrounded by salt marshes with lateral erosion rates of up to 5 m year−1. We collected 6 months of oceanographic data at four moorings within Grand Bay and its tidal channels to assess hydrographic conditions and net sediment-flux patterns and augmented the observations with numerical modeling. The observations imply a divergent sedimentary system in which a majority of the suspended sediment is exported seaward, while a smaller fraction is imported landward via tidal channels, assisting in vertical marsh-plain accumulation, maintenance of channel and intertidal-flat morphologies, and landward transgression. These results describe a dynamic system that is responsive to episodic atmospheric forcing in the absence of a strong tidal signal and the presence of severe lateral marsh loss.

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Publication type Article
Publication Subtype Journal Article
Title Sediment dynamics of a divergent bay–marsh complex
Series title Estuaries and Coasts
DOI 10.1007/s12237-020-00855-5
Volume 44
Year Published 2021
Language English
Publisher Springer
Contributing office(s) Pacific Coastal and Marine Science Center, Woods Hole Coastal and Marine Science Center
Description 15 p.
First page 1216
Last page 1230
Country United States
State Alabama, Mississippi
Other Geospatial Grand Bay
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