Quantification of soil production and downslope creep rates from cosmogenic 10Be accumulations on a hillslope profile

Average soil transport rates over a period of approximately 3500 yr on a convex soil-mantled hillslope have been quantified using a mass-balance model that incorporates the soil concentration of the cosmogenic isotope (super 10)Be. The (super 10)Be model results support the assumption used in most geomorphic models that the soil creep rate is proportional to surface gradient. The predicted diffusion coefficient is 360 + or - 55 cm cubed central dot yr to the negative 1 central dot cm to the negative 1 contour length and the average rate of soil production is 0.026 + or - 0.007 cm/yr. Within the uncertainty of this technique, the data do not reject G. K. Gilbert's hypothesis that some hillslopes may exist in a condition of dynamic equilibrium with a uniform soil production rate. However, the model does not require an assumption of dynamic equilibrium and may be an approach that uniquely allows the quantification of a local soil-production rate law.