We followed several steps to create this summary layer.
We merged the soils GIS coverages obtained from NRCS and
OSU Soil Science Department websites to create a single
soils coverage for the entire study area. We then intersected
this soils layer with the 6th fields layer to attribute
each soils polygon with the appropriate 6th field identifier.
We joined the hydric components tables (from downloaded
Map Unit Interpretations Record Tables) for all relevant
survey areas with the merged soils layer, and queried
the joined tables for hydric components, creating a new
field ("all_hydcode"), with value "hyd" for hydric, "non"
for non-hydric. (Before joining the tables, we had to
edit the Map Unit Interpretations Record Tables and/or
GIS attribute tables to compensate for inconsistent mapping
unit names.) Finally, in the soils summary layer, we summarized
total area of NRCS mapped hydric soils in each 6th field.
In addition, we created a column showing the proportion
of each 6th field watershed occupied by NRCS mapped hydric
soils.
Hydric Soils for
Each Basin
Working either with the soils summary
database or the ArcView layer, you could change the ranges
used to color code each 6th field watershed by the proportion
occupied by hydric soils; you could also color code 6th
fields by the absolute area occupied by hydric soils.
Stream reaches with desirable characteristics, e.g.,
low gradient, can be intersected with areas of hydric soils
to screen for potential restoration projects.
The definition of hydric soils is established
by the National Technical Committee on Hydric Soils.
A list of Oregon hydric soils can be found at:
http://www.statlab.iastate.edu/soils/hydric/sslists.html
Please address questions or comments
to:
Dr. Ralph Garono
Principal Investigator
Earth Design Consultants, Inc.
rgarono@earthdesign.com
Laura Brophy
Principal Investigator
Green Point Consulting
brophyl@peak.org |
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