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Driving east on Highway 36, Cummings Creek is
located between Wilson Creek and Fox Creek monitoring sites but
is actually much closer to Fox Creek. Cummings Creek is a direct
tributary to the main stem Van Duzen River, merging with the main
stem in the lower basin considerably downstream from where it
emerges at the river bar. Cummings Creek runs downstream parallel
to the main stem for a considerable distance before it merges
with the river. The monitoring site is located in the redwoods
with a sizable buffer zone of hardwoods like Red Alder and Oak
within the riparian zone around the stream. Above the site is
a catchment area with about 10.5 miles of stream network. Elevations
in Cummings Creek range from 118 feet at its mouth to over 2.600
feet in the upper reaches, and the monitoring site is approximately
335 feet in elevation. The watershed is completely in private
ownership with most of the timber holdings and timber harvests
by Humboldt Redwood Company (formerly PALCO). Vegetation is predominantly
Mixed and Evergreen (Redwood) Forest throughout. The catchment
area of a monitoring site is important when considering upslope
factors that affect water quality in the stream. This area represents
the true watershed that lies above the point where water from
the stream is sampled, and from which all rain and sediment are
channeled into the stream down to the point where water is withdrawn
for turbidity and suspended sediment analysis.
Stream discharge is directly proportional to the
size of the catchment area - the greater the area, the more water
is carried by the stream during storm events. The Cummings Creek
catchment area is about average in size compared with the other
areas within the project area, and the stream drains an area of
approximately 10.4 square kilometers which is equivalent to 4.0
square miles. During the first year of sampling (HY07) volunteers
recorded a maximum discharge of 239 cubic feet per second (CFS)
and an average discharge of 30 CFS, a maximum turbidity of 852
Nephlometric Units (NTU) and an average turbidity of 92 NTU. In
HY08, there was a maximum discharge of 1,115 CFS and an average
discharge of 132 CFS, a maximum turbidity of 2,380 NTU and an
average turbidity of 237 NTU over the winter sampling season.
Over the two seasons combined (HY07-HY08), the maximum discharge
was in HY08 at 1,115 CFS with an average of 62 CFS, maximum turbidity
was also in HY08 at 2,380 NTU with an average of 139 NTU. This
translates to an average of 1,306 tons of suspended sediment per
square mile per year.
Cummings Creek runs year round at the upper monitoring
site, and is therefore considered to be a perennial stream (as
opposed to an ephemeral stream, which runs dry in the summer).
Maximum weekly average temperature (MWAT) in the summer of 2007
was 15.36 C, and in 2008 it was 14.84 C. Overall, temperatures
were relatively cool compared to many of the other streams sampled
within the lower basin project area, as Upper Cummings Creek,
along with Hely Creek, typically registered the coldest temperatures
of all the streams in the lower basin. Upper Cummings Creek has
a road density of about 8.9 miles of roads per square mile of
watershed. As with all of the catchment areas within the lower
basin, this density of road networks receives a rating of extremely
high. In the 17-year period from 1991 through 2007, the proportion
of the area harvested for timber equaled 110%, with clear cutting
accounting for 10.6% of the total watershed area. Proportions
greater than 100% are possible because areas are calculated to
include re-entry over multiple years. Calculation of overlapping
THPs in forested areas helps quantify the impacts of re-entry
by logging operations over multiple years, and sheds additional
light on a process known as cumulative effects.
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