Exploring Overbank Sediment Deposition Variation in Heavily Modified Floodplains of the Lower Mississippi River: A Sedimentological and Geophysical Analysis

<p>Since the 1930s, the Lower Mississippi River (LMR) has experienced large-scale modifications to the channel profile and surrounding floodplains through dams, dikes, revetments, dredging, and channel cutoffs. Although these changes have improved navigation and reduced flood risk, unanticipated changes to the major flood return period, individual flood severity and duration, and sediment regime have become increasingly apparent and sometimes problematic, such as the 2011 and 2018-2020 floods. Flood control levees along the LMR have reduced the natural floodplain area by 70-90%, resulting in heavily restricted overbank storage capacity of water and sediment. For the same flood events in recent history, Natchez, MS, has experienced record high flood stages and much longer and more severe inundation compared to Vicksburg, MS. This research focuses on integration of clastic sedimentary characteristics and ground-penetrating radar (GPR) data from overbank profiles at Shipland WMA (48 km northwest of Vicksburg) and St. Catherine Creek NWR (18 km southwest of Natchez) using five 6-meter floodplain sediment cores from both locations in meander scroll and backswamp depositional environments. Through analyzing systematic depositional changes through time and testing the capabilities of GPR in delineating subsurface wetland facies, probable event markers for the historic 1973, 2011, and 2018-2020 floods were defined and correlated across each site. These events only remain distinctive due to ¹⁴C temporal estimates; without a scale for time, these flood deposits would be no more distinctive than frequent, minor flood events. GPR is limited to correlation between boreholes and cannot be used to identify flood events alone.</p>

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

Masters Thesis

Year dc:date.available

2024

Author dc:creator

• Fradella, Seth

Contributors dc:contributor

• Dr. Franklin Heitmuller
• Dr. Mark Puckett
• Dr. David Holt

• Lower Mississippi River
• floodplains
• ground penetrating radar
• sedimentology
• Vicksburg
• Natchez
• Geology
• Geomorphology
• Geophysics and Seismology
• Soil Science

Repository record dc:identifier

https://aquila.usm.edu/masters_theses/1056

OAI identifier oai:identifier

oai:aquila.usm.edu:masters_theses-2132