DETERMINING CHANNEL MIGRATION RATES USING SHORT-LIVED RADIOISOTOPES

The limitations of existing methods to quantify fluvial channel geometry changes and lateral migration rates on time scales of tens to hundreds of years have resulted in no universally satisfactory technique. We recently developed a novel technique for determining lateral migration rates using short-lived radionuclides. To further test this technique, we compare lateral migrations rates of the Genesee River, NH determined using ²¹⁰Pb (t_1/2 ~ 22.3 years) in floodplain sediment to rates determined using historical aerial photography. We expect that, as seen previously for the Winooski River, VT, the inheritance of ²¹⁰Pb initial sediment activity) within the deposited sediment affects the absolute surface ages, but that the relative ages of floodplain surfaces determined using ²¹⁰Pb are consistent with the general trend of surface ages recorded in the aerial photography. In continuing work we are also attempting to create a conceptual model for deposition on migrating bends that is consistent with the measured inheritance.