Demonstration of Applied Exercises in Geographic Information Systems
Lower Siletz River, Oregon
ES 341: Fundamentals of GIS
Richard Fletcher, Patrick Stephenson, Earth Science Majors, Western Oregon University,
Monmouth, OR, 97361
Watershed, Sub-basin, & USGS Quads
INTRODUCTION
During the 20th century, thematic maps have been an ever
useful tool for correlating data sets and representing
relevant information. Recent technological advances in
computing, observational data collection, and spacial
referencing, have lead to the advent of Geographic
Information Systems (GIS), which is becoming an ever
powerful and applicable tool for today’s professionals. ES
341 is an entry level GIS class intended to familiarize
students with the concepts and usage of geographic
information systems in real world applications to
watershed analysis. The watershed under discussion
here is the lower portion of the Siletz River, located
primarily in Lincoln County, Oregon. Draining just over
300 square kilometers of area, covering a multitude of
terrain, bedrock, and morphological features, it is an
excellent representation of coastal watersheds.
Specifically for our project we were tasked with creating
maps presenting; watershed coverage, area soils, road
ways, bedrock geologic features, vegetation,
physiographic elevation models, and annual precipitation.
Description: This map depicts the Lower Siletz Water Shed and the eleven 7.5
minute quadrangles that are related.
Table 1: Lower Siletz River Watershed Measurements
Total Drainage Area (sq. meters)
309,762,258.83 Square m
Total Drainage Area (sq. kilometers)
309.76 Square km
Total Length of Watershed (km)
30,000 m, 30 km
Total Width of Watershed
13,500 m, 13.5 km
Length to width ratio
2.222
Total No. of Sub-basins in watershed
18
Average area of sub-basins in watershed
17,209,014 m2, 17.209 km2
Total No. of Steam Segments
2330
Total No. of 1st Order Streams
1,172
Total No. of Second Order Streams
504
First Order Stream Frequency
4.14 (1st order / km2)
Streams & Vegetation
Description: There are three primary vegetative covers . Dominantly covered by
Stika spruce and western hemlock, the Lower Siletz Watershed is also covered by
Douglas Fir, Grand Fir, and Mixed Conifer trees. This variety in vegetative covers
may be due to the relative change in elevation as well as temporal coverage from
North to South.
USGS 7.5 Min DRG Topographic Maps
Description: The watershed is included in seven USGS 7.5 minute topographic
maps. From East to West the watersheds gradient changes drastically from steep
and dissected in the east to a far more gentle meandering system on the west.
Digital Elevation Models
USDA Soil Survey
Table 2: Elevation Analysis
Statistic
Value
Minimum Watershed Elevation
8.5 ft
Maximum Watershed Elevation
2828 ft
Minimum Slope
0۫
Maximum Slope
62 ۫
SUMMARY
This poster presentation is intended to be a final
product showcase of the practical application of
geographic information systems as it pertains
towards earth science. GIS will become an ever
increasingly useful tool by increasing understanding
through graphical representation and comparisons of
statistical and tabular data sets.
Description: There are forty-five unique soil types in the Lower Siletz Watershed.
These soil types are unique to the slope gradients and the flow type of the water.
Many of the soils within this watershed are unconsolidated and are unstable due to
steep gradients and high annual precipitation.
Contour Lines, Roads & Bedrock Geology
Lower Siletz River
Annual Precipitation & Elevation
Description: Digital Elevation Models are extremely useful in analyzing watershed
gradient. These models can show relief in different color schemes for different
uses. This model, for instance, could be used in hazard assessment of land slides
and flooding within the Lower Siletz Watershed.
Digital Ortophohoto Quads
REFERENCES
Source
Data
http://gis.oregon.gov/DAS/EISPD/GEO/sdlibrary.shtml
Vegetation, DOQ
http://libremap.org/data/state/oregon/drg/
DRG
http://jollyroger.science.oregonstate.edu/dem/
DEM
http://www.or.nrcs.usda.gov/pnw_soil/or_data.html
Soil
http://www.wou.edu/las/physci/taylor/es341/es341_w11.htm
Precipitation
http://tin.er.usgs.gov/geology/state/state.php?state=OR
Geology
http://www.wou.edu/las/physci/taylor/es341/es341_w11.htm
Roads, Streams, Watershed
*rfletcher08@wou.edu, *pstephe@wou.edu
Description: Above is a map depicting the bed rock geology with reference to
roads and topography within the Lower Siltez Watershed. The geology observed
at the surface is primarily visible due to the erosive properties the steams and
rivers have worked into the land over long periods of time.
Description: Annual precipitation rates fluctuate within the Lower Siletz
Watershed. The map made above is a vector based model expressing the
igher and lower accumulation amounts annually.
Description: These Digital Orthophoto Quads (DOQs) are georectified 7.5 minute,
10 meter resolution aerial photos with a spatially referenced outline of the Lower
Siletz Watershed.