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On the Interaction of Wetland Loss, Tidal Range, and Tidal Prism: A Case Study in the Mississippi River Delta Plain, Barataria Bay

Nick Howes, Duncan FitzGerald, Ioannis Georgiou, and Zoe Hughes
[email protected]

The spatial pattern of wetland loss in a back-barrier bay determines the magnitude of the increase in tidal prism (the volume of water exchanged via the inlets connecting a basin to the sea). This spatial component is often overlooked, yet this observation has implications for the placement of sediment diversions within inter-distributary bays on the Mississippi Delta. When the tidal wave propagates into a back-barrier basin, its amplitude is attenuated due to frictional and inertia effects, which are a function of inlet configuration, basin geometry, and tidal network. As a result of this interaction, tidal prism is shown to be a non-linear function of wetland loss. Wetland loss in the lower basin results in significantly larger increases in tidal prism per unit area lost, primarily due to the larger tidal range in this region. We quantify this effect in Barataria Bay, LA, by first establishing the theory using standing wave dynamics and non-dimensional analysis, and then by extending this theory using progressive wave dynamics with the aid of numerical modeling. We show that a unit area of land created in the lower basin will reduce prism by ~0.53 m3 compared with ~0.07 m3 if created in the upper basin (tropic tide), a factor of ~7.5. We explore and test several strategies for sediment restoration that include these first order dynamics, and quantify the potential impact of strategies that consider these dynamics versus those that ignore them. This study combines field data, satellite image analysis, and numerical oceanographic modeling.

AAPG Search and Discovery Article #90167©2013 GCAGS and GCSSEPM 63rd Annual Convention, New Orleans, Louisiana, October 6-8, 2013