Transcript Leet and Cruser - Western Oregon University

Yamhill Watershed
Prepared by:
Aquilegia Leet and Jacob Cruser
Earth Science 341
345 N. Monmouth Ave.
Monmouth, OR 97631
Watershed Location
The Yamhill Watershed is located within five counties, including
Yamhill, Lincoln, Polk, Washington and a bit of Tillamook. The
Yamhill River flows East from the Coast Range and eventually
runs into the Willamette River. The Yamhill River begins in
Grande Ronde then passes through towns such as Sheridan
and McMinnville.
Physiology
The Yamhill Drainage ranges from steep tributaries coming out of the
coast range to the meandering sections of the lower portion through the
farmlands and floodplains. The upper, high gradient sections are short
lived as this is an old drainage that has long been eroding the
surrounding hills. Bedrock can be encountered in the streams, but it is
not as common as those rivers coming out of the Cascades. The
vegetation coverage is lush due to high amounts of precipitation and
abundant sources of nutrients from the surrounding hills and
floodplains. Both the extensive stream network and vegetation diversity
can be viewed in figure 1.
Figure 1: Streams over vegetation
Figure 9: DOQ (Digital Orthophoto Quad’s)
Figure 2: The Yamhill
watershed is shown here
in the northwest portion of
Oregon.
General Geology
There is a diverse amount of geology in Oregon. The majority of bedrock in the
drainage is Basalt, which creates some dynamic headwater streams. The lower
elevations of most northwest Oregon streams, including the Yamhill Drainage, are
composed of sedimentary rock in the floodplains. Detailed information about the
bedrock of Oregon can be found through USGS.
Hydrologic Summary
The large amount of streams in the drainage can be viewed in figures 1 & 5. As in
most river systems in Oregon, there is an abundance of tributaries, especially in
the headwaters, where streams quickly develop due to large amounts of
precipitation and come together to form the two major forks (North and South
Fork) to the Yamhill. The lower, meandering section has relatively few tributaries
as it winds its way to the confluence with the Willamette.
Figure 5: Yamhill streams overlaying a model of annual precipitation in the area.
Figure 3: Yamhill Drainage digital
orthographic quadrangles.
Lower Yamhill River.
.
Figure 7: Geology
This is a detailed view of the difference
between the lower elevation rocks and
higher, Coastal Range rocks. In the
basin we have lacustrian and fluvial
sedimentary rocks from the Pleistocene
and Holocene ages. The mountains are
built from volcanics of the Eocene age.
Figure 8: Roads and Highways
Roads in the area consist mostly of rural
roads leading to homes, along with a
plethora of logging roads networking the
surrounding hills. The main highways
bisecting the area are HWYS 18 & 22.
Land use
In the Yamhill drainage 89% of the land is privately owned, while the remaining 11%
is Federally owned. Much of the privately owned land is used for farming and the
forestry Industry. The top three crops produced on these lands are grass seeds,
wheat and Christmas trees. A portion of the land in the surrounding counties has
been set aside for the Grande Ronde reservation.
Figure 4: 7.5’ quadrangles the Yamhill Drainage encompasses.
Figure 6: A digital elevation model of the Yamhill Drainage
Conclusions
The Yamhill Watershed is comprised of many different ecosystems,
bedrocks, soils and vegetation types. like all great rivers the Yamhill
‘is sure to get where it is going and doesn’t want to go anywhere
else”.
~ Hal Boyle
References Cited
Figure 9: Wetlands.
The abundant rainfall in western Oregon
creates a large network of wetlands in the
drainage. The presence of wetlands
creates biodiversity, and biodiversity
increases the health of the ecosystem.
Figure 10: Soils
The soils of the Yamhill watershed vary
greatly, from young sedimentary soils
along the river bed to very well
developed soils on the mountain
slopes.
Google Images
www.google.com/images
Geology Map of Oregon
George Walder and Norman MacLeod. USGS.
Dept. of Agriculture. "Natural Resources Data Department."
Http://www.oregon.gov/DAS/EISPD/GEO/index.shtm
University of Oregon: Geographic information Systems
http://libweb.uoregon.edu/map/map_section/quad_list.htm
USGS website - www.usgs.gov
Professor Taylor’s website - www.wou.edu/taylors