The new 10-Yr El figure eliminates the wavy lines in Figure 2.9, AH703. The new smoothed curves in the figure below are consistent with the accuracy of RUSLE1.06c and 10 yr 24 hr precipitation lines. The new curves also represent how RUSLE1.06c captures main effects associated with how intense erosive storm vary with geographical location and how they affect P factor values.
Estimating R-Values and El Distributions Using RUSLE2 Erosivity Density Curves:
The erosivity density approach was developed to estimate R-values and their monthly distribution for RUSLE2. The erosivity density procedure improves accuracy and consistency, especially in the western US where precipitation data are limited. Erosivity density values are not greatly affected by mountainous terrain and can be estimated with less data than directly computing erosivity values, from detailed rainfall intensity data. Precipitation amount data, which is much readily available than intensity data, is used in conjunction with the erosivity density values to estimate erosivity. A value for monthly precipitation at a location is multiplied by the corresponding monthly erosivity density value given in the figures below to obtain an estimate of monthly erosivity.
(note: This figure should be in the section above related to 10 yr El)
The figures below are maps of erosivity density for the US. A monthly R-value can be obtained by multiplying a monthly erosivity density value by the precipitation amount for that month. The erosivity density value in the figures are in SI units. Monthly precipitation values must be in millimeters (mm) rather than inches to use these erosivity density values. To convert a precipitation value in inches to millimeters (mm), multiply by 25.4. To convert an R-value in SI units to US customary units, divide by 17.02. See AH703 for information on converting between SI and US customary units.
The erosivity density curves apply to all elevations for the summer months and up to an elevation of about 8,000 to 10,000 ft during the winter months. Monthly erosivity values will need to be reduced or even set to zero during the winter where the ground is continuously covered with snow or the soil is continuous frozen so that no erosion occurs.
(note the erosivity density figures below need to go here)
Cover-Management and Ridge Height Codes
RUSLE1.06 uses cover-management, ridge height, and row grade codes. These values much be selected according to RUSLE 1.06c definitions and guidelines so that RUSLE1.06s will give expected results. The document Recommended Option Codes for COVER MANAGEMENT CONDITION (should be in green with a link to the document) provides information to guide the selection of these codes.
New Version of RUSLE1.06c (June 1, 2003)
RUSLE1.06c is a new version that has been placed on the RUSLE1.06 Internet site. RUSLE1.06c contains significant changes so that it will give soil loss values comparable to those given by RUSLE2.