--> Abstract: Morphologic Evolution of a Transgressive Tidal Inlet, Little Pass Timbalier, Louisiana

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Morphologic Evolution of a Transgressive Tidal Inlet, Little Pass Timbalier, Louisiana

Michael D. Miner1, Duncan M. FitzGerald2, and Mark A. Kulp1
1Department of Geology and Geophysics, University of New Orleans, New Orleans, Louisiana 70148
2Department of Earth Sciences, Boston University, Boston, Massachusetts 02215

The majority of changes to barrier island shorelines can be attributed to the influence of tidal inlets, and therefore an understanding of inlet processes is important to effectively manage barrier systems. High rates of relative sea-level rise within the Mississippi River delta plain have resulted in a highly transgressive coastal regime and a rapid landward-migration of barrier island and tidal inlet systems. Moreover, ongoing conversion of back barrier and interior wetlands to open water increases tidal exchange. Enlarging bay-tidal prisms together with the landward migration of the barrier systems results in a dynamic environment within which tidal inlets undergo vast changes in position, geometry, and shoreline morphology.

Historic bathymetric maps (dating to the 1880s) and newly acquired bathymetric data for Little Pass Timbalier are used to construct a series of digital elevation models and ultimately an evolutionary model for the area. The evolution of Little Pass Timbalier is complex and has encompassed periods of landward and lateral channel migration (43 m/yr and 23 m/yr, respectively) and avulsion to breaches along the adjacent barrier shoreline. The breaching event widened the inlet throat from 1.5 km in 1890 to 8.6 km by 1930. The increasing bay tidal prism resulted in inlet widening and the formation of multiple channels separated by ephemeral shoals. During the same time, the ebb tidal delta grew in size and prograded seaward while the adjacent barriers migrated landward.

 

AAPG Search and Discovery Article #90080©2005 GCAGS 55th Annual Convention, New Orleans, Louisiana