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ROCK CREEK WATERSHED ANALYSIS
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Earth
Design Consultants, Inc., Green
Point Consulting, and
Oregon State University Graduate student, Anu
Gupta worked together together with the Siletz Watershed
Group (SWG) to complete a Watershed Assessment for the Rock
Creek watershed in the Siletz River basin. This fifth-field
watershed is located at the intersection of Polk, Benton and
Lincoln Counties in the Coast Range of Oregon. |
Purpose for this watershed
assessment
The
primary goals of this assessment were to inventory and characterize
watershed components and to evaluate watershed processes that influence
abundance and distribution of salmonids and other valued wildlife.
Products from this work include: a series of monitoring and management
action recommendations; summary and base map geographical information
system data layers; and identification of important data gaps and
recommendations for filling those gaps.
In
this assessment, we want to emphasize that watershed processes themselves,
such as landslides and sediment transport, cannot be characterized
as either good or bad. Instead, we need to address the likely impact
of these processes on valued resources within the watershed through
detailed study. For example, landslides are a natural component
of Pacific Northwest watersheds. The same landslides and debris
flows that choke streams with fine sediments and silts are also
an important source of gravel necessary for salmon spawning. Landslides
may be a concern wherever human actions have altered their frequency,
magnitude, and position in the watershed.
In
this assessment we address important issues within the Rock Creek
watershed that were identified by the Siletz Watershed Group in
1997 (SWG 1997). These issues include water quality and quantity;
aquatic and fish habitat; slides and erosion control; and land use.
All of these issues are key to this assessment, and are also components
of the 1997 GWEB Draft Watershed Assessment Manual (Non-Point Source
Solutions 1997).
Methodology
for this watershed assessment
In
conducting this assessment, we used methods that had the following
characteristics:
- GIS-based,
using base maps developed from Geographic Information Systems
data and terrain information derived from Digital Elevation
Models (DEMs). We elected to use ArcView and ArcView Spatial
Analyst as our principal tools in this analysis. Both
of these software packages are relatively low in cost and can
be run on most modern personal computers. We performed this
entire analysis, with the exception of the merging of the DEM
files and the reprojection of new layers, in ArcView;
- Integrative,
synthesizing the many factors influencing watersheds and the
interactions of those factors;
- Quantitative,
making use of numeric data as much as possible while still incorporating
supplementary qualitative information;
- Scientific,
using existing data in a scientifically valid way. Wherever
possible, we used quantitative and documented data sets;
- Model-driven,
using conceptual models of watershed processes to guide analyses
and interpretation of results.
Publications
Brophy, L. and R. J. Garono.
2000. GIS as a Tool for Watershed Assessment: Working Toward a Desktop
Decision Support System. Proceedings of the 17th International Conference
of The Coastal Society, Portland, OR USA. 592.
Garono, R. J. and L. Brophy.
1999. Using A Geographic Information System (GIS) To Prioritize
Monitoring And Restoration Activities In An Oregon Coastal Watershed.
Proceedings of American Water Research Association.
Rock Creek (Upper Siletz) Watershed
Analysis
The report and figures are in PDF
format and range in size from 100 to 1,600K.
You will need the Adobe Acrobat Reader to view the files.
The Acrobat Reader is free and can be downloaded from www.adobe.com.
A hard copy of this report is available from the MidCoast
Watersheds Council.
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Contact Information
Wetland & Watershed Assessment Group
Earth Design Consultants, Inc.
230 SW Third St., Suite 212
Corvallis, OR 97333
(541) 757-7896
(541 757-7991 FAX
http://www.earthdesign.com
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