Methodology and Interpretation

Percent urban
The percentage of urban land cover is calculated by dividing the number of urban land cover cells in the reporting unit by the total number of land cover cells in the reporting unit minus those cells classified as water (i.e., total land area). High amounts of urban land indicate substantial modification of natural vegetation cover and may have profound effects on wildlife habitat, soil erosion, and water quality.

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 Census 2000 (c2k) - Metadata

• United States Roads (Wessex / GDT) - Metadata