Methodology and Interpretation

Rainfall-derived erosivity [R factor] (unitless)
This metric is a RUSLE weighted-average rainfall-derived erosivity metric, which is derived from a PRISM 2-km grid, and is computed on a cell-by-cell area basis. An increase in soil erosivity may indicate an increase in the amount of runoff of sediment and chemical constituents associated with sediment (e.g., phosphorus) to streams and lakes. Because soil erosion is correlated with phosphorus runoff and the amount of sediment in the water column of streams or lakes, the modeled erosion of soil in a watershed may be an indicator of eutrophication or the diminution of water clarity in surface water. These models are responsive to soil characterization precision, thus computed and actual erosion values may vary.

Quantile: Each class contains an approximately equal number (count) of features. A quantile classification is well-suited to linearly distributed data. Because features are grouped by the number within each class, the resulting map can be misleading, in that similar features can be separated into adjacent classes, or features with widely different values can be lumped into the same class. This distortion can be minimized by increasing the number of classes. For continuity of the browser content, and consistency among maps, legend gradients are from higher values (red) to lower values (green).

Metric input GIS data:

• 244 Subwatersheds - Metadata

• National Elevation Dataset (NED) - Metadata

• National Land-Cover Dataset (NLCD) - Metadata

• Stream Network - Metadata

• STATSGO - Metadata