rainfall-runoff erosivity factor. It is the average annual summation (EI)
values in a normal year's rain. The erosion-index is a measure of the
erosion force of specific rainfall. When other factors are constant, storm
losses from rainfall are directly proportional to the product of the total
kinetic energy of the storm (E) times its maximum 30-minute intensity (I).
Storms less than 0.5 inches are not included in the erosivity computations
because these storms generally add little to the total R value. R factors
represent the average storm EI values over a 22-year record. R is an
indication of the two most important characteristics of a storm
determining its erosivity: amount of rainfall and peak intensity sustained
over and extended period.
R Factor Map for Michigan
From Technical Guide to RUSLE use in Michigan, NRCS-USDA State Office of Michigan.
|Copyright ©2002 Institute of Water Research, Michigan State University|