HR: 15:25h
AN: H52D-08    [PDF]
TI: Conservation Relations for Cosmogenic Radionuclides: Application to Erosional Landscapes
AU: * Parker, G
EM: parke002@umn.edu
AF: St. Anthony Falls Laboratory, University of Minnesota, Mississippi River at 3rd Ave SE, Minneapolis, MN 55414 United States
AU: Perg, L
EM: lperg@umn.edu
AF: St. Anthony Falls Laboratory, University of Minnesota, Mississippi River at 3rd Ave SE, Minneapolis, MN 55414 United States
AB: Cosmogenic radionuclides have proved to be a useful tracer allowing quantification of rates of erosion and transport of sediment and concomitant geomorphic change. In numerical models of morphodynamics, differential sediment transport is tracked using the Exner equation of conservation of sediment mass. Here a corresponding equation is developed to describe the conservation of a cosmogenic radionuclide. The combination of two equations of conservation, one for sediment mass and one for the radionuclide tracer, offers a powerful way to extend the amount of information that can be extracted from analysis of cosmogenic radionuclides. The general formulation is applied to the specific case of an eroding landscape with stochastic elevation fluctuations. In many applications to date the rate of erosion is directly tied to the concentration of cosmogenic radionuclides at the eroding surface, but the sediment sampled for radionuclides is often obtained from a river not far from the area of interest. Such river samples represent averages over an erosion rate that includes stochastic fluctuations of elevation. It is demonstrated that a failure to include these fluctuations can lead to an overestimate of the erosion rate by as much as a factor of two. A scheme is presented by which cosmogenic radionuclides can be used to estimate not only the mean erosion rate, but also the standard deviation of temporal fluctuations in bed elevation.
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
DE: 1869 Stochastic processes
DE: 1886 Weathering (1625)
SC: Hydrology [H]
MN: 2003 Fall Meeting