Testing a mechanistic soil erosion model with a simple experiment

A simple experiment was used to test the development of a “shield” over the original soil and associated changes in sediment concentrations as described in the mechanistic Rose erosion model. The Rose model, developed for rain-induced erosion and sediment transport on hillslopes (J. Hydrol., 217 (1999) 149; Trends Hydrol., 1 (1994) 443), was applied to a simple experimental set-up, consisting of a small horizontal soil surface (7×7 cm2) under constant shallow (5 mm) overland flow with raindrop impact. The soil consisted of two particle size classes, clay and sand, greatly simplifying the analytical solution of the Rose model by reducing the unknown system parameters to one, the soil detachability. Photographic documentation of shield formation corroborated the conceptual validity of the Rose model. Using a single, best-fit value for the soil detachability, quantitative agreement between modeled and experimental results is excellent (R2=0.9). This research provides lucidity to the primary processes enveloped in the Rose model and these mechanisms can be extrapolated to more complicated or realistic systems in which the individual processes may be more difficult to recognize.