USDA Agricultural Handbook #703 - Predicting Soil Erosion by Water: A Guide to Conservation Planning with the Revised Universal Soil Loss Equation (RUSLE) - R factor on page 48, LS Factor on page 124

Web Soil Survey (K - Soil Erodability Factor)

ITD Roadside Revegetation Manual

NOAA Precipitation Data

USGS Streamstats interactive mapping tool

Rainfall Erosivity Factor Calculator