Determining lateral migration rates of meandering rivers using fallout radionuclides
Black, E.; Renshaw, C.E.; Magilligan, F.J.; Kaste, J.M.; Dade, W.B.; Landis, J.D.
Geomorphology 123.3-4
2010
ISSN/ISBN: 0169-555X DOI: 10.1016/j.geomorph.2010.08.004
Accession: 037032234
We explore the novel technique of using short-lived fallout radionuclides to date fluvial surfaces with the goal of determining lateral migration rates. Specifically, we use the fallout radionuclide(210) Pb (half-life t(1/2) approximately 22.3 years) to determine the lateral migration rates of meandering reaches on the Winooski River, VT, the upper Connecticut River, NH, and the Genesee River, NY. We find that, particularly near the channel,(210) Pb(ex) inventories are affected by the initial(210) Pb(ex) inventories of freshly deposited sediment (inheritance). Inheritance differs at each site, with lower inheritance occurring at sites with larger upstream drainage areas. After accounting for inheritance,(210) Pb(ex) inventories in surface sediments along a transect orthogonal to the channel yield migration rates of 0.7, 3.1, and 4.7 m/y for the Winooski, Connecticut, and Genesee Rivers, respectively. These rates agree well with values derived independently from historical aerial photography. Variations in(210) Pb(ex) inventories along the transects also provide details of the channel migration histories not evident from the limited available aerial photographs, including evidence for both nearly constant linear and episodic channel migrations. Results suggest the broad applicability and added value of our approach for quantifying decadal-scale variations in fluvial surface ages.