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 Metrics > Riparian Characteristics > Metric Map (ragt30), Natural Breaks, Methodology and Interpretation
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Methodology and Interpretation

RAGT30 - Percent total agricultural within 30 meters of streams
The percentage of all agricultural land cover 30 meters 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 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. 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.

Metric Map (ragt30), Quantile Metric Map (ragt30), Natural Breaks

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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