A conceptual model for determining soil erosion by water



Current estimates of rates of soil erosion by water derived from plots are incompatible with estimates of long-term lowering of large drainage basins. Traditional arguments to reconcile these two disparate rates are flawed. The flux of sediment leaving a specified area cannot be converted to a yield simply by dividing by the area, because there is no simple relationship between flux and area. Here, we develop an approach to the determination of erosion rates that is based upon the entrainment rates and travel distances of individual particles. The limited available empirical data is consistent with the predictions of this approach. Parameterization of the equations to take account of such factors as gradient and sediment supply is required to proceed from the conceptual framework to quantitative measurements of erosion. However, our conceptual model solves the apparent paradox of the sediment delivery ratio, resolves recent discussion about the validity of erosion rates made using USLE erosion plots, and potentially can reconcile erosion rates with known lifespans of continents. Our results imply that previous estimates of soil erosion are fallacious. Copyright © 2004 John Wiley & Sons, Ltd.