HR: 0800h
AN: H51E-0815    [Abstracts]
TI: Dating Fluvial Floodplains and Quantifying Channel Migration Rates Using Short-Lived Radioisotopes
AU: * Black, E E
EM: Erin.E.Black@Dartmouth.edu
AF: Dartmouth College, Hinman Box 6105, Hanover, NH 03755, United States
AU: Renshaw, C E
EM: Carl.E.Renshaw@Dartmouth.edu
AF: Dartmouth College, Hinman Box 6105, Hanover, NH 03755, United States
AU: Kaste, J M
EM: James.M.Kaste@Dartmouth.edu
AF: Dartmouth College, Hinman Box 6105, Hanover, NH 03755, United States
AU: Magilligan, F J
EM: Francis.J.Magilligan@Dartmouth.edu
AF: Dartmouth College, Hinman Box 6105, Hanover, NH 03755, United States
AU: Dade, W B
EM: William.B.Dade@Dartmouth.edu
AF: Dartmouth College, Hinman Box 6105, Hanover, NH 03755, United States
AB: A variety of methods, including dendrochronolgy and aerial photography, have been used previously to quantify fluvial channel geometry changes and lateral migration rates on time scales of tens to hundreds of years. However, no universally satisfactory technique has emerged due to various limitations of each method. We explore the novel technique of using short-lived radionuclides to date fluvial surfaces with the goal of determining lateral migration rates. In particular, we use 210Pb (t(1/2) ~ 22.3 years) in floodplain sediment to determine the lateral migration rates of regulated reaches on the Genesee River, NY, and unregulated reaches on the Winooski River, VT and the upper Connecticut River, NH. Surface ages and lateral migration rates are compared to those determined using historical aerial photography. Preliminary analyses of sediment cores are consistent with the general trend of surface ages recorded in the aerial photography, but the absolute ages of the surfaces indicate that inheritance of 210Pb within the deposited sediment affects the surface ages. Furthermore, the temporal resolution of the method is much greater in areas with rapid migration over the past 50 years than in those areas with similarly rapid migration occurring in years prior to 1960.
DE: 1040 Radiogenic isotope geochemistry
DE: 1808 Dams
DE: 1820 Floodplain dynamics
DE: 1825 Geomorphology: fluvial (1625)
SC: Hydrology [H]
MN: 2007 Fall Meeting