Methodology and Interpretation

Roughness coefficient (unitless)
This metric is a SEDMOD weighted-average Mannings' n surface roughness coefficient. An increase in surface roughness may indicate a decrease the amount of runoff to streams and lakes, which may contain sediment, road salts, or other compounds.

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.

Metric input GIS data:

• United States Hydrologic Units (8-digit HUCs) - Metadata

• United States Coastal Change Analysis Program (CCAP) - Metadata

• United States National Elevation Dataset (NED) - Metadata

• United States STATSGO Soils - Metadata