Methodology and Interpretation
RAGT0 - Percent total agricultural adjacent to streams
The percentage of all agricultural land cover adjacent to streams is calculated
by summing the total number of pasture, crop and orchard 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. Animals grazing in pasture
land may decrease vegetation cover possibly leading to increased runoff. Livestock
may also impair stream banks by trampling riparian vegetation, which may cause increased
sedimentation in the stream.
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
* EMAP-West Landscape Metrics Metadata (FGDC)