Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Civil and Environmental Engineering

First Advisor

John H. Pardue


The exchange of carbon, sediment, and water between brackish marshes and a shallow, fine-grained bay of the Barataria Bay Estuary were examined in order to quantify the production, transport, and storage of carbon in the Barataria Basin. Factors controlling these exchanges were identified and measured. Flux of suspended sediments through a tidal bayou connecting marshes and open waters were measured throughout the year and during a variety of weather events. Discharge of porewater from the marsh substrate to surrounding waters via subsurface flows and surficial drainage channels were measured. Constituent concentrations in the marsh runoff were monitored and used to distinguish porewaters from surface waters. Results indicated that the bayou discharges sediment during typical summer conditions and imports sediment during winter. Late summer storms, occurring during the annual period of highest water level, are the largest sedimentary events and result in large net imports of sediment. The bayou/marsh system is a net importer of sediments from the bay. Sediment flux is controlled by water level in relationship to marsh surface elevation, wind speed, direction, and duration, tidal prism volume, and seasonal factors such as invertebrate activity in the marsh. An extensive network of surficial channels or rivulets exists on the marsh surface, resulting in porewater discharge from parts of the marsh that are distant from the bayou. Porewater seepage into rivulets cannot account for the volume of discharge observed. Diffusion of porewater constituents into a thin surface layer of water and flow of the layer toward the rivulet is suggested as the primary route of constituent discharge.