HR: 0800h
AN: H41C-0307    [Abstracts]
TI: Wetland Platform Erosion by Wave Action and its Implications for Future Mitigation Projects in South Louisiana
AU: * Wilson, C
EM: cwilson2@tulane.edu
AF: Tulane University, Dept. of Earth and Environmental Sciences, New Orleans, LA 70118 United States
AU: Allison, M
EM: malliso@tulane.edu
AF: Tulane University, Dept. of Earth and Environmental Sciences, New Orleans, LA 70118 United States
AB: The transition of marshland to open water in south Louisiana continues at an alarming rate, and freshwater diversions and marsh restoration projects have been implemented or are planned to address this loss. This project examines the magnitude and impact of wave-induced subaqueous platform erosion that occurs during and following subsidence of the subaerial marsh. Study and control sites have been chosen in Breton Sound, where an existing freshwater diversion project (Caernarvon) has been operational since 1991; Barataria Bay, where the Davis Pond diversion has been active since 2003; and the Deltas National Wildlife Refuge (DNWR), where marshes are still receiving significant freshwater and sediment from the Mississippi River. Study grids are established along marsh fringes in bay-fronting, gulf-fronting, and interior ponds that have a variety of orientations and open water fetch to predominant wave attack and in recent years (since the 1930s) have shown significant wetland loss. Subaqueous platform elevation and stratigraphy are examined with vibracores and transit elevation transects and detailed bathymetric maps of the 1 km grids are also made with an Odom Hydrotrak HT100 fathometer. Preliminary results suggest that the overall magnitude of wave-induced erosion is extreme (deflation of 1-1.5 m) in Barataria Bay sites, but may not be as great a magnitude in Breton Sound or the DNWR sites. Shoreline orientation to wave attack, the composition and resistance to wave re-working of the underlying sediment, or the presence of submerged aquatic vegetation (SAV) that serves to stabilize the substrata may help explain the resultant site to site variability. Predominant in many sites, once the aerial marsh has submerged, a portion of the peat deposits is preserved below more recent onlapping bay bottom sediments.
DE: 1815 Erosion and sedimentation
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting