Authors: Lisa Davis*, University of Alabama, Ray Lombardi, University of Alabama, Christopher Lance Stewart, Murray State University, Gary Stinchcomb, Murray State University , Steve Forman, Baylor University, David S. Leigh, University of Georgia
Topics: Geomorphology, Paleoenvironmental Change, Physical Geography
Keywords: floods, paleofloods, rivers, geomorphology, stratigraphy
Session Type: Poster
Start / End Time: 3:05 PM / 4:45 PM
Room: Lincoln 2, Marriott, Exhibition Level
Presentation File: No File Uploaded
Paleoflood analyses provide insight into long-term flood frequency and magnitude changes. We reconstructed a 2,200 year-long record of floods on the Tennessee River (USA) from a 3.5 m sediment core sampled from a relict terrace. We measured particle size distributions at 1 cm intervals (Malvern Mastersizer 3000). End member analysis of particle size distributions suggested medium to coarse sand was the particle size fraction likely resulting from flood deposition. After controlling for the influence of channel proximity on the supply of sand using change point analyses, we identified paleoflood layers based on medium to coarse sand peaks we identified using local polynomial regression analyses, stratigraphic descriptions, and micromorphology images. A combination of optically stimulated luminescence and Bacon age modeling was used to determine paleoflood ages. The sediment core contained numerous paleoflood deposits from the last 2,200 years and included the flood of record, an 1867 C.E. flood. We estimate four of the paleofloods were larger than the flood of 1867 C.E. based on their higher medium-coarse sand content relative to the 1867 C.E. flood deposit. Floods that occurred in the last 1000 cal. yrs. B.P. were more moderate in size than the floods that occurred in the 1000 yrs. prior, if medium to coarse sand concentration is assumed a surrogate for flood magnitude. Confidence in the interpretation of paleoflood magnitude could be improved if more modern floods were preserved in the core. Nonetheless, these findings raise important questions worthy of further investigation regarding flood frequency and magnitude in the late-Holocene.