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Methodology and Interpretation
RAGC0 - Percent cropland adjacent to streams
The percentage of cropland cover adjacent to streams is calculated by
dividing the number of cropland land cover cells underneath stream segments in
the 3 km grid cell reporting unit and dividing by the stream corridor's total
land area (total number cells underneath stream segments minus those classified
as water). Agricultural practices typically employ fertilizers, pesticides and
other chemicals that may be transported to streams in water runoff. The closer
agriculture is to a stream the more likely related pollutants will enter the
stream. Concentrations of pollutants transported into streams are also more
likely to be higher when agriculture is closer to streams.
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)
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