Tracking sediment redistribution in a small watershed: Implications for agro-landscape evolution

A new, multi-tracer method is used to track erosion, translocation, and redeposition of sediment in a small watershed, thus allowing for the first time a complete, spatially distributed, sediment balance to be made as a function of landscape position. A 0(.)68 ha watershed near Coshocton, Ohio, USA was divided into six morphological units, each tagged with one of six rare earth element oxides. Sediment translocation was evaluated by collecting run-off and by spatially sampling the soil surface. Average measured erosion rate was 6(.)1 t ha(-1), but varied between 40.4 t ha(-1) loss from the lower channels to 24.1 t ha(-1) gain on the toeslope. With this technique it was possible for the first time to itemize the sediment budget for landscape elements into three components: (1) the soil from the element that left the watershed with run-off; (2) soil from the element that was redeposited on lower positions, with the spatial distribution of that deposition; and (3) soil originating from the upper positions and deposited on the element, with quantification of relative source areas. The results are incongruous with the current morphology of the watershed, suggesting that diffusion-type erosion must also play a major role in defining the evolution of this landscape. Copyright (C) 2004 John Wiley Sons, Ltd.