Raindrop‐induced saltation and the enrichment of sediment discharged from sheet and interrill erosion areas

Sheet and interrill erosion areas are sources of soil material rich in nutrients and pollutants. The loss of soil, nutrients and other chemicals from these areas is a matter of concern both in terms of maintaining soil productivity and the health of offsite environments. Many experiments on rainfall erosion have shown enrichment of fine material, nutrients and other chemicals in the sediment discharged for sheet and interrill erosion areas, but often these results were obtained over short periods of time. A qualitative mechanistic model of raindrop‐induced saltation is used to illustrate how this transport mechanism influences the composition of sediment discharged by rain‐impacted flow. Initially, fast moving particles are enriched in the sediment discharge but, over time, during a rainfall event, slower moving particles become more represented. Raindrop‐induced saltation promotes the storage of material on the soil surface with a coarser composition than the original soil. Winnowing of material from this storage by the development of flow‐driven saltation during high‐intensity events can modify the composition of the sediment discharged later by raindrop‐induced saltation. Given stable soil particles, the composition of the sediment discharged at the steady state is the same as the original soil. Enrichment is a non‐steady‐state phenomenon and failure to recognize the transient nature of enrichment may lead to inappropriate interpretation of the implications of the results from short‐term experiments. Copyright © 2011 John Wiley & Sons, Ltd.

[1]  Kristof Van Oost,et al.  The impact of agricultural soil erosion on biogeochemical cycling , 2010 .

[2]  P. Kinnell.  The influence of raindrop induced saltation on particle size distributions in sediment discharged by rain-impacted flow on planar surfaces , 2009 .

[3]  Wolfgang Schwanghart,et al.  Agricultural soil erosion and global carbon cycle: controversy over? , 2009 .

[4]  G. Larionov,et al.  Equation of sediment transport for slope flows , 2006 .

[5]  P. Kinnell.  Simulations demonstrating interaction between coarse and fine sediment loads in rain‐impacted flow , 2006 .

[6]  P. I. A. Kinnell,et al.  Raindrop‐impact‐induced erosion processes and prediction: a review , 2005 .

[7]  T. Strickland,et al.  Variable rainfall intensity effects on carbon characteristics of eroded sediments from two coastal plain ultisols in Georgia , 2005 .

[8]  D. W. Reeves,et al.  Mineralogy of eroded sediments derived from highly weathered Ultisols of central Alabama , 2002 .

[9]  P. Kinnell.  Particle travel distances and bed and sediment compositions associated with rain‐impacted flows , 2001 .

[10]  C. Alonso,et al.  Numerical Study of the Maximum Boundary Shear Stress Induced by Raindrop Impact , 1991 .

[11]  C. Rose,et al.  Sorbed Chemical Transport in Overland Flow: II. Enrichment Ratio Variation with Erosion Processes , 1991 .

[12]  W. P. Miller,et al.  Particle Size of Interrill-eroded Sediments from Highly Weathered Soils1 , 1987 .

[13]  I. Moore,et al.  Kinematic overland flow — Generalization of Rose's approximate solution, Part II , 1985 .

[14]  O. G. Engel.  Initial Pressure, Initial Flow Velocity, and the Time Dependence of Crater Depth in Fluid Impacts , 1967 .

[15]  G. Hofman,et al.  Enrichment of Organic Carbon in Sediment Transport by Interrill and Rill Erosion Processes , 2008 .

[16]  P. Kinnell.  SEDIMENT CONCENTRATIONS RESULTING FROM FLOW DEPTH/DROP SIZE INTERACTIONS IN SHALLOW OVERLAND FLOW , 1993 .

[17]  Calvin Wyatt Rose,et al.  Sorbed chemical transport in overland flow. I, A nutrient and pesticide enrichment mechanism , 1991 .

[18]  C. Rose,et al.  Soil erosion processes and nutrient loss. II. The effect of surface contact cover and erosion processes on enrichment ratio and nitrogen loss in eroded sediment , 1990 .

[19]  C. Rose,et al.  Soil erosion processes and nutrient loss. I, The interpretation of enrichment ratio and nitrogen loss in Runoff sediment , 1990 .

[20]  P. I. A. Kinnell,et al.  Transport of a Noncohesive Sandy Mixture in Rainfall and Runoff Experiments 1 , 1978 .