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Miner, M. D., Kulp, M. A. and Fitzgerald, D. M., 2007. Tidal Versus Shoreface Ravinement Surfaces and Tidal Inlet Fill Preservation Potential, Mississippi River Delta Plain, U.S.A. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 805 – 809. Gold Coast, Australia, ISSN 0749.0208 Barrier island and tidal inlet systems along the Mississippi River Delta Plain are undergoing rapid morphological change due to shoreface retreat and increasing bay tidal prism, driven by high rates of relative sea-level rise (RSLR) (1 cm/yr) and interior wetland loss, respectively. Two adjacent tidal inlets, Little Pass Timbalier and Raccoon Pass, exhibit contrasting morphology and sediment regimes. Little Pass Timbalier is ebb-dominated with a deep main channel (10 m), enlarging ebb-tidal delta, and negligible flood tidal delta. Contrastingly, Raccoon Pass is flood-dominated with a shallow main channel (4 m), negligible ebb-tidal delta, and enlarging flood-tidal delta. Sediment cores, shallow subbottom profiles, and comparisons of historic bathymetric maps (since the 1800's) and recent bathymetric data allowed a determination of the depth of shoreface ravinement and the geometry and extent of tidal inlet fill deposits preserved by retreating tidal inlets. Results show that the depth of shoreface ravinement in this area is greater than 10 m, which exceeds the deepest tidal ravinement depths. Raccoon Pass has a low preservation potential due to its shallow depth and small sized ebb delta. In contrast, the prograding ebb delta at Little Pass Timbalier protects and stabilizes its deep ebb channel, which will allow backfilling of the channel to occur before complete excavation during shoreface retreat. The subsidence driven RSLR coupled with ebb-tidal delta progradation increases the potential of tidal inlet fill preservation because the distance between the tidal ravinement and shoreface ravinement surfaces is continually increasing with time. [ABSTRACT FROM AUTHOR]