This project demonstrates the many components of working with ArcView GIS software. Compiled is a complete set of GIS vector map themes, Digital Elevation Models (DEMS), Digital Raster Graphics (DRGs) and other GIS data for Gale Creek Watershed.

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Gale Creek Watershed in Washington County, Oregon
Prepared by Pamela Monnette ES 492 GIS
Applications in Earth Science
Hydrologic Summary The watershed has 10
subbasins and contains 17 tributaries. Streams
are fed primarily by precipitation. Most streams
in the low lying parts of the watershed have
been channelized and wetland areas have been
drained for agriculture use.
Introduction This project demonstrates the
many components of working with ArcView GIS
software. Compiled is a complete set of GIS
vector map themes, Digital Elevation Models
(DEMS), Digital Raster Graphics (DRGs) and other
GIS data for Gale Creek Watershed.
General Geology The oldest geologic materials
in the Gales Creek Watershed and volcanic and
sedimentary rocks formed during the Eocene and
Oligocene ages of the Tertiary period. The
volcanic rocks and mostly basaltic lavas and
tufts, overlain by sedimentary rocks made up of
shale, claystone, sandstone, and siltstone. There
are 11 soil associations listed in the Natural
Resources Concervation Service (NRCS) Soil Survey
of Washington County. Soils in the Coast Range
are well-drained silt loam and cobbly loam. The
nearly level flood plains consists of young
alluvium, silt, and clay deposits approximately
20 to 30 feet thick. The historic wetland areas
have eight hydric soil types which are generally
very deep, poorly drained, and have slow surface
runoff. The entire watershed is underlain by
sandstone 400 feet thick (Breuner).
Watershed Location Gale Creek Watershed is
located in the northwestern corner of Oregon and
is contained almost completely in Washington
County. It is one of many large watersheds in the
Tualatin River Basin. It is situated on the
eastern side of the Coast Range Mountains.
This figure was achieved By clipping a larger
stream network to the area of the Quadrangles
that Gales Creek Watershed resides in.
The figure on the right represents the types of
Timber in Gales Creek Watershed with the streams
in the area overlain on top of it.
The watershed is entirely within the Northwestern
edge of Washington County, except for 2 small
portions extending into Tillamook County.
Above is a figure showing the distribution of
bedrock Geology within Gales Creek Watershed. The
colors Are represented by codes that correspond
to different Types of rock. Overlain onto this
theme, is a map of Major highways.
Physiography The watershed ranges in
elevation from a low of 159 ft. above sea level,
at the confluence with the Tualatin River, to its
highest point of 3,154 ft. The mainstem of Gales
Creek is 23.5 miles long and flows in a
southeasterly direction. Land designations
promote the rural character of the watershed by
limiting land uses to forestry, agriculture,
scattered rural residences, and rural services.
Almost two-thirds of the watershed is privately
owned (Breuner).
Timber and Vegetation The watershed contains a
mosaic of native and exotic plant species. The
original forested uplands, most of which was
logged 40 to 80 years ago or burned in two
stand-replacing fires in 1933 and 1945, known as
the Tillamook Burn, have been replaced with
Douglas-fir forests which are intensively
managed. Furthermore, black cottonwood, bigleaf
maple, Oregon ash, vine maple and elderberry are
the dominant plant species in the riparian zone
of Gales Creek (Breuner).
Gales Creek Pictures
On the left is a Digital Elevation Model of all
of the Quads that make up Gales Creek Watershed.
The darker areas represent higher elevations,
while the lighter areas represent
lower elevations.
DEMs
Climate The climate with the watershed is
marine-influence with an extended winter rainy
season. Summers tend to be hot and dry with
little rainfall. The Coast Range Mountains form
the upper north and Western boundaries of the
watershed, separating it from the Pacific Ocean
to the west. The mountain slopes tend to be steep
with high gradient streams.
Digital Orthophotos of Gales Creek Watershed
Quadrangels
DOQs
Conclusions This project focused on finding and
displaying various GIS data for Gales Creek
Watershed. It included assembling DRG, DEM, DOQ,
bedrock geology, precipitation, soils, vegetation
(timber), streams and road themes in the form of
our particular watershed.
This is a figure displaying the precipitation in
inches annually received in Gales Creek
Watershed.
Here we see an image of digital raster graphics
with an outline of the Gales Creek Watershed
boundary overlain on top of the quads.
References Cited Breuner, Nancy. (1998). Gales
Creek Watershed Assessment Project. Tualatin
River Watershed Council.
and DRGs!