Millicoma River Drainage Basin

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Millicoma River Drainage Basin Coos and Douglas
Counties Oregon
Prepared by Earth Science 341Students W.
Vreeland, D. Fulks, R. Rios
Introduction The Millicoma River watershed lies
on the Western part of central Oregon. It lies
mainly in Coos County with portions in Douglas
County. There are few true roads in this remote
area. There is one highway (OR 241) in the
southwest corner. Most roads are dirt roads with
a few concrete, aggregate, and other hard
surfaced roads. The total drainage area for the
Millicoma River watershed is 390,363,098 sq
meters. The total length East to West is 30.07
kilometers and the North to South is 27.96,
giving length to width ratio of 11.075. The
total number of sub basins in the watershed is
13. The average area of the sub basins is 30.07
square kilometers. Physiography Elevation The
highest elevation of this watershed is 734
meters while the lowest point is just 3 meters
above sea level. The maximum slope is 65
percent. The average slope is 24 percent. Some
areas are completely flat.
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Physiography continued Stream Order There are
3337 stream segments flowing through the
watershed. 1679 are first order stream segments
and 775 are second order stream segments. There
is one main river (West Fork Millicoma River)
running through the west side from the north to
the south. The first order stream frequency is
4.29 streams per square kilometer.
Geology There are five different geologic units,
Qal (Alluvial deposits), Tsr (Siletz River
Volcanic and related rocks), Tss (Tuffaceous
siltstone and sandstone), Tt (Tyee Formation),
and Ty (Yamhill Formation and related rocks).
Precipitation The annual precipitation ranges
from 65 to 87 inches of rainfall per year, with
the higher rainfall levels being at the higher
elevations. Soils The soils are primarily
silty loam at higher elevations with mixed
amounts of silty loam, clay, and sand at lower
elevations. Land Ownership The land in this
watershed is owned primarily by the Weyerhaeuser
Corporation or is state forest land. The
majority of the land remaining is privately
owned, Lone Rock/ Sun Studs owned, or owned by
the Menasha Corporation. Vegetation The majority
of the vegetation is dominated by Douglas
Fir-Western Hemlock and Mixed Conifer and
Broadleaf Forest. Sitka Spruce-Western Hemlock
forests cover a relatively small section at the
south west. Only a small portion of the south
east has recently harvested areas. The vast
majority of the area has Merchantable Timber and
most of the northern part has been burned are
restocked. The cut over areas restocked and
cutover areas not re-stocked make-up a small
section. The furthest south west area is
non-timber. 1914 Fire Areas burned in the 1914
fire have regenerated forest canopy regardless of
whether they were replanted. The Weyerhaeuser
corporation holds land that were not
significantly effected by the fire. The state
forest lands consist primarily of areas that were
replanted after the 1914 fire.