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Methodology and Interpretation
RURB30 - Percent urban within 30 meters of streams
The percentage of urban land cover within 30 meters of a stream is calculated
by summing the number of urban 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. High amounts of urban land indicate
substantial modification of natural vegetation cover and may have profound
effects on wildlife habitat, soil erosion and water quality. The closer urban
land is to a stream the more likely it will have adverse affects on the stream
habitat and water quality.
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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