Methodology and Interpretation

Percent urban within 120 meters of wetlands
The affect of runoff from areas adjacent to wetlands may be strongly influenced by land cover type that occupies a zone (i.e., a buffer zone), up to approximately 120 meters from the edge of a wetland. Thus, the percentage of urban land cover within 120 meters of wetlands is calculated by summing the total number of urban land cover cells within a four cell buffer (120 meters) zone on the perimeter of wetland patches in the reporting unit and dividing by the area of the buffer plus the area of the buffered wetland. Cells outside buffer zones for wetlands within each reporting unit are ignored. Other buffer distances may be more appropriate, depending on the runoff chemical constituent(s), flow dynamics, soil conditions, position of wetland in the landscape, and other landscape characteristics.

Standard Deviation: Classes show the amount a feature's attribute value varies from the mean value of the distribution. Class breaks are generated by successively adding or subtracting the standard deviation from the mean. A two-color ramp is best used to emphasize values above or below the mean. It is particularly useful in viewing spatial variability of a parameter.

Metric input GIS data:

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

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