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Research Project: Understanding Water-Driven Ecohydrologic and Erosion Processes in the Semiarid Southwest to Improve Watershed Management

Location: Southwest Watershed Research Center

Title: Rainfall erosivity: An overview of methodologies and applications

item YIN, S. - Beijing Normal University
item Nearing, Mark
item BORELLI, P - University Of Basel
item XUE, X. - Beijing Normal University

Submitted to: Vadose Zone Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/27/2017
Publication Date: 12/14/2017
Publication URL:
Citation: Yin, S., Nearing, M.A., Borelli, P., Xue, X. 2017. Rainfall erosivity: An overview of methodologies and applications. Vadose Zone Journal. 16(12):1-16.

Interpretive Summary: Rainfall erosivity is an index that describes the power of rainfall to cause soil erosion. This study presents an overview of rainfall erosivity, primarily concentrating on the methods used to calculate and map it in the United States and around the world. Data from China and Italy were used to evaluate differences between the various methods of calculating the erosivity values, and we found that the current USDA-ARS RUSLE2 method provides eh most robust numbers. This method is used extensively in the United States by the USDA-Natural Resources Conservation Service in daily planning for implementing on-farm conservation plans and policies, but not commonly known around the world. The quantification of erosivity is based on the energy and intensities of rainfall events. The formulas for computing erosivity have changed somewhat over the years based on new scientific results. There has been some confusion, primarily outside of the U.S., regarding the appropriate equations to use for calculating rainfall erosivity. This paper helps to clarify the physical basis of the concept, and guide the user in choosing the appropriate sets of equations to use for greatest accuracy. The result of the paper will be better implementation of USDA science both inside the U.S. and around the world

Technical Abstract: The rainfall erosivity factor (R-factor) is one of six erosion factors in the Universal Soil Loss Equation (USLE), together which reflect the combined effects that cause soil loss by rill and interrill erosion on hillslopes by precipitation. It is defined as the summation of event EI30 (the product of kinetic energy and maximum 30-min intensity) over a year, and calculated based on rainfall hyetograph data. The development of the R-factor in the various versions of the USLE was reviewed, including the definition of the individual event and the criterion for selecting events used in the calculation, the equation used to estimate the unit kinetic energy from the rainfall intensity, the estimation of erosivity from the snowmelt and thaw, and erosivity mapping. Most research on rainfall erosivity deals with any of three aspects: developing estimation methods for deriving erosivity from courser resolution rainfall data (such as daily, monthly and annual) but with greater spatial and temporal coverages compared to those from hyetograph data, preparing erosivity maps including those for annual average, monthly and 10-yr recurrence erosivity, and documenting temporal trends in erosivity. Rainfall erosivity research on the above three aspects were summarized to provide a greater understanding of the R-factor.