Transcript North Yamhill River Watershed – Yamhill & Washington County, Oregon Prepared by: Courtney A.

North Yamhill River Watershed – Yamhill & Washington County, Oregon
Prepared by:
Courtney A. Stowell
ES 492
INTRODUCTION
Physiography
The North Yamhill River watershed consists of 445 miles of waterways and covers
113,441 acres (177 square miles), almost entirely in Yamhill County, Oregon.
There is a small part of the watershed that is located in Washington County. (See
figure 2)
Most of the land in the Yamhill Watershed is privately owned (approximately
87%), with the majority of land uses in agriculture (60%) and industrial forestry
(37%). Although the predominant land uses in the North Yamhill River Watershed
are agriculture and forestry, urban areas are growing rapidly. The elevation ranges
from approximately 50 feet to 1050 feet. (See figures below)
Maximum Elevation – 1043 feet
Minimum Elevation – 20 feet
Maximum Slope – 66.21
Minimum Slope – 0
Watershed Location
Hydrologic Summary
The North Yamhill River consists of the following major tributaries: Panther Creek,
Baker Creek, Haskins Creek, Fairchild Creek, Yamhill Creek, and Turner Creek.
(See figure 10) Stream flow in the North Yamhill watershed varies throughout the
year, largely depending on the amount of rainfall. (See figure 11) The high and low
flows have different impacts on the landscape and resources. The total drainage
area is 457,275 sq. km. The length of the watershed is 29 km and the width is
18.5 km. Some other facts include: total number of streams – 2162, first order
streams – 1096, and second order streams – 510.
The North Yamhill River starts in the eastern side of the Coast Range, flowing
south and east to its convergence with the Yamhill River, just southeast of
McMinnville. (See figure 1) The Yamhill River then drains into the Willamette River
near Dayton.
Figure 6 - DOQs
Figure 5 - DEMs
Figure 10 - Streams
Figure 1 – Map of Oregon & North
Yamhill River watershed
Figure 7 - DRGs
Physiography Continued
Figure 2 – Counties watershed
encompasses
General Geology
Figure 6 displays vegetation and the most abundant kind is Douglas Fir and
Oak-Douglas Fir. The Annual Rainfall for this particular watershed ranges from
40-120 inches inches per year. The figures below consists of: Vegetation Map
and Annual Rainfall Map. (See figures 8 & 9)
Figure 11 – Streams on
Precipitation
The General Geology (Bedrock) of the North Yamhill River Watershed consists of
mainly is Quaternary Sediment (Qs), Siletz River Volcanics (Tsr), and the Yamhill
formation consisting of marine sedimentary rocks (Ty). The main soils of this
watershed correspond with the bedrock. So Qs has silty valley soil whereas Tsr
and Ty are more rocky soils (cobbly and stoney) found on hillslopes. (See figures
3 & 4).
Figure 8 – Vegetation
Notice in the figure above
that most of the vegetation
consists of Douglas Fir.
Figure 3 – Geology
(Bedrock)
Conclusions
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Figure 9 – Precipitation
Figure 4 – Soil Map
There are many different types
of soils in the North Yamhill
River Watershed
Annual Rainfall - Climate Map
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The North Yamhill River watershed is unusual, as it encompasses two
counties: Yamhill and Washington.
The watershed is sub-divided into 24 sub-basins with an average area 19053
sq. km.
The Geology consists of 3 major bedrocks: Qs, Tsr, and Ty with certain soil
characteristics associated with each.
There are two major vegetation groups: Douglas Fir and Oak-Douglas Fir.
Stream discharge is highly precipitation controlled in the North Yamhill
watershed. Stream flow parallels precipitation throughout the year.
References Cited
Schmit, L. Denise. "2005 Interim Report - North Yamhill River subwatershed."
Yamhill Basin Council 2005 8-9. 21 Mar 2007
<http://www.co.yamhill.or.us/ybc/Monitoring/Interim2005WQMPreportFINAL.pdf>.