A2. Influence of Antecedent Moisture Conditions on Inter-rill Soil Erosion
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van Meerveld, Ilja (H.J.)
Few studies have looked at the effects of antecedent soil moisture conditions on inter-rill soil erosion and in many models soil erodability parameters are considered constant, even though it is well known that the soil’s inherent ability to resist erosion varies temporally due to differences in temperature, soil frost, time since ploughing, consolidation, microbial activity, soil organic matter content, soil moisture, etc. Therefore, 11 high rainfall intensity (>45 mm/hr) experiments were done on the 6-m × 2-m EPFL erosion flume to determine the effects of antecedent moisture conditions on inter-rill soil erosion. Pore pressure at 0.05 m below the soil surface at the start of the experiment had a large effect on peak sediment concentrations; wetter antecedent moisture conditions led to higher peak sediment concentrations, with the largest changes occurring near saturation. Antecedent moisture conditions also influenced the composition of the eroded sediment; wetter conditions led to a disproportionately large flux of clay- and silt- sized particles. The finding that the composition of the eroded sediment not only changes during an event but is also dependent on the antecedent moisture conditions has important implications for modelling the transport of chemical fluxes associated with the sediment flux, such as phosphorous fluxes. Antecedent moisture conditions did not influence the steady-state sediment concentrations. One of the optimized non-dimensional parameters in the analytical solutions of the Hairsine-Rose erosion model (α, the ratio of the re-detachability of the soil and runoff depth to the runoff ratio and the mass per unit area of sediment required for complete shielding) was linearly related to pore pressure at the start of the experiment. Using the linear relation between this non-dimensional parameter and pore pressure, the sediment concentrations and the composition of the eroded sediment could be simulated for a range of antecedent soil moisture conditions and events. This work builds on Dr. Parlange’s contributions to erosion research and finding analytical solutions to describe erosion processes, and is another step towards operational soil erosion models that can be used under a wide range of conditions.
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Internet-First University Press
soil erosion; particle size; antecedent soil moisture conditions; EPFL erosion flume; Hairsine-Rose model