Rain-Impact-Entrainment of Chemicals and Soil into Runoff: Simple Experiments
Abstract
A series of simple experiments were developed to isolate and investigate the rain-impact-induced entrainment of soil and chemicals into overland flow. The Rose model, a mechanistic soil erosion model, was adapted to these experiments to account for both soil and chemical transport. The Rose model was originally derived for hillslope erosion and these experiments test the interactions between soil erosion processes and chemical movement from the soil into overland flow. Particular attention is given to roles of surface shielding, the process in which, over-time, a shield of deposited material develops, increasingly shielding the underlying soil from additional erosion. Water ponded on the surface may, if deep enough, also reduce soil detachability. In this study the original Rose model is reduced to fit a series of different experiments designed to isolate a few processes. All experiments utilize a small (~50 cm2) horizontal soil surface exposed to simulated rainfall, the intensity of which is systematically changed over an order of magnitude (10-100 mm hr-1). In one set of experiments the ponded depth and overland are held constant and in the other set the ponded depth is dynamic and the overland flow is zero. The soils used in this study are combinations of one or two particle size classes representative of clay and sand (148-153 m). The soils are saturated with water containing chloride and phosphorus prior to commencing rainfall. Soil and chemical concentrations are measured throughout each simulated rainfall. In all cases, the Rose model agrees well with the soil erosion data and agrees with the early portions of the observed chemical concentration trends. The chemical data clearly indicate how a Rose-model approach can be used to simulate chemical transfer and, furthermore, what processes are captured and missed by other hypothesized models. Because of the experimental simplicity, the physical processes are easily visualized and the mathematical description readily understood.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2002
- Bibcode:
- 2002AGUFM.H22B0898P
- Keywords:
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- 1815 Erosion and sedimentation;
- 1871 Surface water quality;
- 3210 Modeling