32 Hydrogeology
Added due to amount of discipline abstracts submitted.
Tuesday, 10 March 2026
1:30 PM - 5:30 PM
RCC, 106
Embanked Floodplain Sedimentation Patterns and Rates Along the Lower Mississippi River Since the Early 20th Century
Paper number: 32-6
Program: Technical Sessions
Time: 3:00 PM – 3:15 PM
Authors
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Paul HudsonLeiden University College The Hague, The Hague
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Seth FradellaThe University of Southern Mississippi, Hattiesburg, MS
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Shara GremillionThe University of Southern Mississippi, Stennis Space Center, MS
Abstract
A synthesis of sediment core data, ground-penetrating radar profiles, and contemporary overbank flood deposit samples collected from embanked floodplains of the Lower Mississippi River (LMR) between Greenville, MS, and St. Francisville, LA, reveals a wide variety of historical sedimentation patterns and rates. Prior to completion of flood-control levee installations and channel cutoffs, major historical floods in 1927 and 1937 deposited large volumes of sand in the vicinity of natural levees and crevasses. Thereafter, large floods have become less effective for introductions of overbank sediment, particularly fine-grained sediment in distal floodplain settings. Indeed, average sedimentation intensities have steadily decreased from 2.6 mm/day during the 1973 flood to 0.2 mm/day during the 2020 flood, tracking well-documented historical declines in suspended-sediment loads. Ironically, increasing flood frequency and durations in the vicinity of Natchez, MS, have sustained annual overbank sedimentation rates that compare well with long-term historical values (~2.5–3.5 cm/year). Further, localized areas adjacent to chutes and crevasses near the main LMR channel are hydraulically favorable sites for rapid overbank sedimentation. Finally, increases in sand and silt percentages at the expense of clay in the upper 50–100 cm of sediment cores indicate that distal meander scroll and backswamp settings have experienced more energetic overbank flows following completion of flood-control infrastructure, which limits the effectiveness of carbon and nutrient retention in the embanked floodplains.
Geological Society of America Abstracts with Programs. Vol. 58, No. 1
doi: 10.1130/abs/2026SE-411636
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