Aquatic Sciences Meeting, Albuquerque 2001

PC09 River and Margin Biogeochemistry

Date: Wednesday, February 14, 2001

Location: Southwest Hall

Coakley, B, J, Tulane University, Department of Geology, New Orleans, LA, 70118, USA, bcoakle@tulane.edu

Allison, M, A, Tulane University, Department of Geology, New Orleans, LA, 70118, USA, malliso@tulane.edu

REPEAT SWATH MAPPING AT ENGLISH TURN; DIRECT IMAGING OF BEDFORM MIGRATION AND SEDIMENT STORAGE IN THE LOWER MISSISSIPPI RIVER

Repeat swath mapping of the bottom surface of the Mississippi River, supported by precision navigation, can be used to directly image changes in the river bed through the construction of difference maps. These maps can be used to study the localization of deposition and erosion on the bed and put quantitative estimates on the net flux of sediment through particular stretches of the river. Using a Reson SeaBat 8101 (240 kHz; 101 beams; 150° swath), we have mapped a section of the Mississippi River near English Turn, about 8 miles below New Orleans, in February and May 2000. Difference maps constructed from these survey grids show changes in the bottom ranging mostly between -1 and +1 meters. Migrating sand waves and longer wavelength bedforms are obvious. Over the entire grid, the bathymetric differences average to near zero, suggesting that there has been little net sediment export from this 10 mile stretch of the river during the last, relatively weak flood cycle. Further mapping, tied to the river's flood cycle, is planned for 2001.

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Aquatic Sciences Meeting, Albuquerque 2001

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