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Title Human and climate influence on floodplain sedimentation in the Upper Little Tennessee River valley, southern Blue Ridge Mountains, USA
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This research examines a millennial-scale history of sedimentation in the Upper Little Tennessee River valley within a 363 km2 catchment of the Southern Blue Ridge Mountains. The focus is on late prehistoric and historic overbank floodplain sedimentation rates, deriving flood records from the sedimentology, and relating the stratigraphy and sedimentology to past land use and climate. Stratigraphy, particle size, and geochronology (radiocarbon, luminescence, and cesium-137) data were measured at three mainstem floodplain sample sites from core samples and outcrops, dating back at least 1200 years before present. Particle size was measured in continuous down-column overbank sediment samples (1-3 cm increments). Results indicate that late prehistoric sedimentation rates were less than 1 mm/yr, whereas historical sedimentation rates are about an order of magnitude higher (0.5 to 17.0 mm/yr). Furthermore, the most rapid historical sedimentation rates of 13-17 mm/ yr occur after 1960. These latest high rates of floodplain sedimentation correspond to a time period of population growth in the region that is characterized by second home construction, road construction, and other erosive land uses related to population and infrastructure growth in the region. Comparison of particle size data with post-1945 stream gage data indicates that the percent frequency of >0.25 mm particles is a good indicator of the frequency of large overbank floods, but that less information is provided about flood magnitude. Particle size data thus indicate that the highest frequency of large floods occurs after 1960, relatively few large floods occurred circa 1910-1960, whereas several large floods occurred during the peak time of timber harvest in the region circa 1875-1910, and around the Medieval warm period. The sedimentary data are correlated with known oscillations in climate, including frequency of tropical storms and observed wet versus dry periods.

Contributors D. S. Leigh and Lixin Wang

Leigh, D.S. and Wang, L. 2011. Human and climate influence on floodplain sedimentation in the Upper Little Tennessee River valley, southern Blue Ridge Mountains, USA. In: International Quaternary Union (INQUA) XVIII Congress: 58 Quantifying and modelling human and climatic impacts on hillslope and fluvial sediment dynamics during the Holocene. International Quaternary Union, Bern, Switzerland.

Key Words alluvium, osl, radiocarbon, sediment, vertical accretion
File Date 2011
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