Using sediment travel distance to estimate medium-term erosion rates: A 16-year record

摘要

Fine grained (80-μm) magnetite was introduced onto a semi-arid grassland hillslope in 1992, as part of a set of rainfall-simulation experiments. Using measurements of magnetic susceptibility, the median distance travelled by these magnetite grains during subsequent natural runoff events in the 16-year period up to 2008 was estimated. Coupling this estimate to direct measurements of sediment flux obtained during the rainfall-simulation experiments has enabled estimation of the erosion rate over this period. The estimated average erosion rate of between 2.61 × 10~(-2) and 4.36 × 10~(-2)-kg-m~(-1) year~(-1), is equivalent to a rate of ground lowering between 0.020 and 0.033-mm year~(-1). This estimate is consistent with (in the sense of being less than) an estimate of total sediment detachment over the same period. The rate of erosion measured using this travel-distance approach is an order of magnitude less that obtained from a study based on ~(137)Cs in a nearby catchment, and compatible with the longevity of continents.