Methodology and Interpretation

RWETL30 - Percent wetland within 30 meters of streams
The percentage of wetland cover within 30 meters of a stream is calculated by summing the number of wetland land cover cells underneath stream segments in the 3 km grid cell reporting unit and within a one cell buffer (30 meters) and dividing by the stream corridor's total land area (all cells 30 meters adjacent to streams minus those classified as water). Cells inside the buffer zone but outside of the grid cell boundary are ignored. Forests and wetlands act as filters, removing pollutants from runoff before it enters streams. Forests and wetlands also provide habitat for a wide variety of valuable plant and wildlife species.

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.

Natural Breaks: Classes are based on natural groupings of data values. Natural break points are identified by looking for groupings and patterns inherent in the data. The features are divided into classes whose boundaries are set where there are relatively large jumps in the distribution of data values.

* EMAP-West Landscape Metrics Metadata (FGDC)