General Technical Report
Overview of the Caspar Creek Watershed Study1
1An abbreviated version of this paper was presented at the Conference on
Coastal Watersheds: The Caspar Creek Story, May 6, 1998, Ukiah, California.
2 Forester II, Research and Demonstration Program, Jackson Demonstration
State Forest, Mendocino Ranger Unit, California Department of Forestry and
Fire Protection, 802 N. Main St., Fort Bragg, CA 95437. (firstname.lastname@example.org).
Abstract: The California Department of Forestry and Fire Protection
(CDF) and the Pacific Southwest Research Station, Redwood Sciences
Laboratory (PSW) have been conducting watershed research within the Caspar
Creek watershed on the Jackson Demonstration State Forest, in northern
California, since 1962. A concrete broad-crested weir with a
120 low-flow V-notch was constructed in both the 473-ha North Fork and 424-ha South Fork of
Caspar Creek by the late fall of 1962. Both watersheds supported predominantly
second-growth stands of coast redwood (Sequoia
sempervirens (D. Don) Endl.) and Douglas-fir (Pseudotsuga
menziesii (Mirb.) Franco) averaging 700
m3 ha-1 of stem wood. The study has been conducted in two phases. The South Fork
phase was designed as a traditional paired-watershed study and involved
monitoring the impacts of road construction and selection harvesting by tractor
on streamflow, suspended sediment, and bedload. Approximately one-third of
the watershed was logged in each year from 1971 to 1973, starting with the
most downstream area. Several publications have documented the results from (1)
the calibration and roading activities (1962-1971) and (2) the logging activity
and subsequent monitoring through 1976. Planning for the North Fork phase
started in the early 1980's. This study phase was initiated in response to new
federal legislation requiring the evaluation of cumulative watershed effects as a part
of management activities. The principal objective was to test for
cumulative watershed effects (CWE) resulting from timber harvesting and related activities.
The North Fork became the treatment watershed and was divided into
13 sub-basins including three control watersheds to be left untreated. Ten
Parshall flumes and three rated sections were installed in the watershed one at
the outflow of each of these sub-basins. A new sampling system called SALT
was developed along with the necessary sampling software and hardware
Total timber volume removal in North Fork was slightly less than in
the South Fork (about 50 percent); however, harvesting activities were limited
to eight discrete clearcut harvest blocks ranging from 9 to 60 ha, occupying
35-100 percent of individual subwatersheds in the CWE study area. These
harvest units were logged using primarily skyline cable yarding techniques. Road
and landing construction and tractor logging were limited to ridgetop and
upper slope locations. Auxiliary studies examining summer low flow, soil pipe
flow, bedload movement, geochemical response, and biological aquatic effects
were also monitored during this period. Monitoring began in 1985 and
harvesting was done over a 3-year period (1989-1992). Harvesting began in the
upper third of the North Fork watershed to aid in detecting the existence of
possible CWE's. Monitoring was maintained at all gaging stations through
hydrologic year 1995. After 1995, a long-term monitoring plan was instituted. This
plan uses a subset of the gaging stations (SF, NF, A, C, D, E, H, I) to monitor
the possible long-term effects of timber harvesting on stream discharge,
suspended sediment, and bedload.
overview of the history, site characteristics, major events,
equipment, and sampling systems used during the life of
the Caspar Watershed Study will provide background for the
following papers in these proceedings.
Historical Land Use in the Study Area
Considerable disturbance of the inner gorge and channel
areas occurred in the Caspar drainage before management by the State
of California and the implementation of this study. The
2,167-ha Caspar watershed, like most north coast watersheds, was subject
to intensive land-use practices spanning decades during the early
old-growth logging era.
The first European settlement in the area was before the
1860's. The watershed and neighboring village were named after a
local trapper, Siegfried Caspar. In 1860, the Caspar Logging
Company was founded, the owners having purchased most of the
Caspar Creek watershed. A sawmill was built at the mouth of Caspar
Creek, ultimately producing up to 25,000 board feet of lumber per
day. Jacob Green Jackson, after whom Jackson State Forest is
named, bought the mill in 1864 and soon after had three log crib dams
built on Caspar Creek. They were constructed of log cribbing with a
rock and soil core with a flume and spillway through the center.
A triggering mechanism enabled the operator to open the
spillway gate when the natural stream flow was judged high enough.
The dams were built to provide additional stream discharge for river
log drives, permitting logging operations to be expanded into the
upper reaches of Caspar Creek. Thirty thousand logs or more were
often tiered in the channel, waiting to be floated down to the mill
during high winter flows. Log drives required a full reservoir and a
storm capable of raising the water level of the stream by about 2
feet. Francis Jackson, a local historian who found remnants of many
crib dam sites on the local streams, estimated from historical
archives that an average of two log drives per winter took place in each of
the North and South Fork drainages (Napolitano 1996).
Clearcut logging was used exclusively during this era. The
felled areas were broadcast burned to remove obstructions before
yarding the old-growth logs by oxen teams over skid trails to "roll
away" landing type areas near the stream channels. Logs were then
jack screwed into the creek to form log tiers that would be
floated downstream during the winter high flows. These activities
involved extensive excavation into inner-gorge slope areas. Years
later, railroads were expanded into upper reaches of some
watersheds, and semi-mechanized yarding of remote canyon tributaries
was made possible using railway inclines (also called
tramways) powered by steam donkeys. For example, one incline was built
to yard logs from the Dollard-Eagle subwatershed over the ridge to
the railway in Hare Creek. Most of the watershed had been logged
the late 1890's, and by 1906, a quiescent period followed as
Caspar Lumber Company moved eastward in search of new timbered
areas to harvest. Harvest activities did not begin again until the
early 1960's, after the State took over management of the area.
Caspar Watershed Study Genesis
As the State started harvesting many of the second-growth stands
in the historically logged areas, more information was needed on
the effects of logging and road-building on sedimentation and
aquatic habitat. The impetus for beginning a joint study with federal
and state agency cooperators in 1960 was to answer such questions as:
(1) What are the water and sediment production of north
coast watersheds that have been undisturbed for many years?, (2) How
are water yield, water quality, flood peaks, and stream
sedimentation affected by current road-building and logging practices?, and
(3) What changes take place in the channel after logging, and how
do these changes affect fish and their habitat? (Anonymous 1963).
Early participants besides the California Department of Forestry and
Fire Protection (CDF), Jackson Demonstration State Forest, and the
Pacific Southwest Forest and Range Experiment Station (PSW),
Redwood Sciences Laboratory, included Humboldt State University,
California Department of Fish and Game, and the University of California.
Staff from the California Department of Water Resources, and
U.S. Geological Survey also participated in an advisory capacity at
the initial design stage of the study.
The study is located in the Caspar Creek Experimental Watershed
on the Jackson Demonstration State Forest (Preface, fig. 1,
these proceedings). The watershed study encompasses 897 ha of the
North and South Forks of Caspar Creek in northwestern California.
The basins are located about 7 km from the Pacific Ocean at
approximately 39°21'N, 123°44'W and have a general west-southwest
orientation. The North and South Fork weirs are approximately 14 and 15
km, respectfully, southeast of Fort Bragg, California.
Topography and Soils
Topographic development consists of uplifted marine terraces
that are deeply incised by coastal streams. About 35 percent of
the basin's slopes are less than 17° and 7 percent are steeper than
35°. The hillslopes are steepest near the stream channel with
inner-gorge slope gradients of 50 percent or more. A slope
change typically occurs 100 m to 350 m upslope, becoming more
gentle near the broad and rounded ridgetops. The elevation of
the watershed ranges from 37 to 320 m.
The soils in the Caspar Creek study basins are
well-drained clay-loams 1 to 2 m in depth, and are derived from
Franciscan sandstone and weathered coarse-grained shale of the
Cretaceous Age. They have high hydraulic conductivity, and
subsurface stormflow is rapid, producing saturated areas of only limited
extent and duration (Wosika 1981). Three soil complexes are dominant
in the study area. The Vandamme, Irmulco-Tramway, and
Dehaven-Hotel series occupy the upper, mid, and inner-gorge
areas, respectively. The first two complexes account for approximately
90 percent of the area.
A Mediterranean climate is typical of low-elevation watersheds
on the central North American Pacific coast. The fall and
winter seasons are characterized by a westerly flow of moist air
that typically results in low-intensity rainfall and prolonged
cloudy periods with snow occurring rarely. In the spring, this
weather pattern migrates northward, and rainfall becomes much
less frequent. Summers are relatively dry, with cool coastal fog
that typically can extend 16 km or more inland during the
summer, often burning off to the coast by midday.
Temperatures are mild with muted annual extremes
and narrow diurnal fluctuations due to the moderating effect of
the Pacific Ocean. Average monthly air temperatures between
1990 and 1995 in December were 6.7 °C, with an average minimum of 4.7
°C. Average July temperature was 15.6 °C, with an average maximum
of 22.3 °C (Ziemer 1996). The frost-free season ranges from 290 to
365 days. Mean annual precipitation from 1962 through 1997 was
1,190 mm, with a range from 305 to 2,007 mm. Ninety percent of the
total annual precipitation falls between October and April. The
frequent occurrence of summer coastal fog makes a small, but
unknown, contribution to the total precipitation in the form of fog
drip. Snowfall is rare at these low elevations in this region.
The forest vegetation of this coastal region is the product
of favorable climatic and soil conditions. The area supports
dense stands of second-growth Douglas-fir (Pseudotsuga
menzieii (Mirb.) Franco), coast redwood (Sequoia
sempervirens (D. Don) Endl.), western hemlock
(Tsuga heterophylla (Raf.) Sarg.), and grand
fir (Abies grandis (Dougl. ex D. Don) Lindl.). There are also
minor components of hardwoods, including tanoak
(Lithocarpus densiflorus (Fook. and Arn.) Rohn) and red alder
(Alnus rubrus Bong.), and scattered Bishop pine
(Pinus muricata D. Don). A few old-growth redwoods remain within the Caspar Creek
watershed. The timber stands average 700 m3
ha-1 of stem wood.
Understory vegetation includes evergreen
huckleberry (Vaccinum ovatum Pursh), Pacific rhododendron
(Rhododendron macrophyllum D. Don), and sword fern
(Polystichum munitum (Kaulf.) Presl.).
The South Fork Phase
The initial South Fork study was designed as paired
watersheds. Both watersheds are initially untreated until sufficient data
have been accumulated to allow the variable(s) of interest to
be predicted from the control watershed (Thomas 1980).
One watershed was then logged and the other remained unlogged
as a control. The South Fork was chosen to be the treated
watershed because it had older and larger second-growth timber
stands while the North Fork was designated to serve as the
control (Preface, fig. 1, these proceedings).
Precipitation Monitoring System
Five standard manually-read rain gages were installed in
both watersheds in 1961 (Tilley and Rice 1977). One
weighing-type recording gage was placed near the confluence of the North
and South Forks in fall 1962. A second recording gage was located
near the North Fork weir in August 1964. These 8-inch recording
gages could chart 7 days of rainfall data and were the primary system
until 1989. The network was measured on a weekly basis through most
of the South Fork study phase. Some gage locations were
changed when the study transitioned into the North Fork Phase.
Streamflow, Suspended Sediment and Fisheries Monitoring System
Concrete broad-crested weirs with an inset 120 low-flow
V-notch were constructed in both the North and South forks of
Caspar Creek by November 1962 (Krammes and Burns 1973).
Stream discharge data were collected throughout the South Fork
phase (1962-1976) using A-35 stream
recorders3 mounted on stilling wells. Suspended sediment data were collected with
fixed-stage samplers mounted on the weirs. The watersheds were
calibrated from 1963 through 1967. From 1978 through 1982,
sediment sampling instrumentation was upgraded to a PS-69
automatic pumping sampler installed at each weir.
Flow-proportional frequency controllers were added later to increase the efficiency
of the sampling and to reduce the processing workload. All of
the automatic sampling was supplemented and calibrated using
DH-48 manual grab-samplers to perform depth-integrated hand
samples. Several different sampling algorithms were used through 1984
to trigger the sampler, including sediment proportional, flow and
time modes. Since 1983, ISCO pumping samplers have been the
primary sediment sampling instrument.
3The use of trade or firm names in this publication is for reader information
and does not imply endorsement by the U.S. Department of Agriculture of
any product or service.
In cooperation with the California Department of Fish
and Game (DFG), a fish ladder and control dams for fisheries
research (Kabel and German 1967) were completed in November 1962
on the South Fork, but not finished on the North Fork until
August 1963. A counting weir was also installed 2.5 km upstream from
the ocean in November 1964, but it was severely damaged during
the December 1964 storm and was never used for any extended
fish monitoring. DFG monitored the fisheries until 1964 and
then discontinued its participation. PSW contracted with University
of California at Davis to study fish habitat by monitoring
stream bottom fauna before and after road building and logging in
the South Fork (Anonymous 1963).
Debris Basin Measurements and Maintenance
Debris settling basins behind the weirs have been surveyed
annually since 1962 to account for deposited suspended sediment
and bedload. During the summer low-flow period, permanently
placed pins are used for a sag tape measurement of about two
dozen transects in each weir pond. Measurements from the current
year are compared to the previous year to obtain the volume of
Periodically these basins are drained and the
sediment excavated so that the gaging accuracy of the weir is not
diminished. The basins are surveyed before and after excavation. During
the fifth clean-out, in 1988, core samples were taken to determine
the grain-size of the deposited debris. Debris removal was
initially accomplished by building a truck ramp over the weir so that
heavy equipment could excavate and remove the debris. Eventually,
an access road was built to the back of each debris basin to
provide better access for sediment removal.
In summer 1967, about 6.8 km of logging roads were
constructed near the canyon bottom in the South Fork. Of these, about 6
km were within 61 m of the stream, of which 2.3 km directly
impinged on the stream channel. About 5 percent of the watershed
was occupied by main line and spur roads (Wright 1985). Fill
slopes, landings, and major areas of soil exposed by road-building
were fertilized and seeded with annual ryegrass in September
1967, immediately after completion of the road. The following 3
years were used to evaluate the effects of road construction on
streamflow and sedimentation (Krammes and Burns 1973).
After the road evaluation phase, harvesting began in the South
Fork in March 1971 and ended in September 1973 (Preface, fig. 1,
these proceedings). Single-tree and small-group-selection silviculture
was used with ground-lead tractor log yarding. Most of the
landings were located near the canyon bottom. The watershed was
divided into three sale units of approximately equal size. Starting in
the most downstream unit, harvesting progressed upstream, one
unit each year. In the first sale (Watershed #1), 60 percent of the
timber volume was harvested over 101 ha. The Watershed #2 timber
sale removed about 70 percent, covering another 128 ha. The final
sale, Watershed #3, harvested about 65 percent of the timber from
176 ha. In total, about 153,000 m3 of timber were removed from
the South Fork watershed (Tilley and Rice 1977). More than 15
percent of the watershed was compacted from skid trail, landing, and
road construction. Skid trail construction accounted for more than
half of that compaction, and road construction accounted for more
than one-third (Wright 1985).
Landslide/Soil Erosion Surveys
CDF conducted a landslide survey in the South Fork during
summer 1976. Soil displacements larger than about
50 m3 ha-1 were measured. These data were compiled to estimate the soil displacement of
mass movements occurring in the watershed in a post-logging state.
Similarly, PSW installed seven plots as part of a larger study
to assess soil movement associated with various logging systems.
The plot locations centered on existing landings, with
additional transects to measure the cross-sectional area of rills, gullies,
ruts, and cuts made for skid trails or roads.
The North Fork Phase
Conception and Planning
Planning for this phase of the study started in the late 1970's.
Impetus for this study was to respond to new regulatory requirements, both
at the federal and state levels, that significantly affected
resource management activities. The National Environmental Policy Act
(NEPA) and Public Law 92-500 mandated the consideration of
"cumulative effects" as part of Environmental Impact Statements. The North
Phase of the study was designed to quantitatively test the magnitude
of cumulative watershed effects (CWE's) associated with
suspended sediment, storm runoff volume, and streamflow peaks (Rice 1983).
A system of 13 nested subwatersheds (Preface, fig. 2,
these proceedings) was selected to quantitatively evaluate
whether synergistic cumulative effects were occurring
(table 1). These subwatersheds were selected on the basis of size and location
to assist in tracing sediment through many sizes of watersheds.
They ranged in size from 10 ha (BAN) to 384 ha (ARF). Eight
are tributary non-nested subwatersheds. The DOL station gages
a tributary containing one nested subwatershed (EAG).
The remaining four are progressively larger nested mainstem
gaged subwatersheds. The subwatersheds were named after people
who lived and worked in the local area during the early logging
era (with the exception of watershed Munn). The North Fork
phase was designed to address the question: For any given intensity
of storm and management impact, does watershed response
increase with watershed area? Cumulative effects are discussed in a
broader context by Reid (these proceedings).
Table 1-Subwatershed names, areas, and treatment chronology.
Precipitation, Solar Radiation, Air, and Water Temperature
Six rainfall monitoring sites were operated during this phase.
Five of the sites had been monitored since 1962. An additional site
was installed in 1987 on the northerly ridge of the North
Fork watershed. Tipping-bucket rain gages replaced the
recording weighing type gages in 1989 and provided greater resolution
by electronically recording a measurement every 5 minutes. In
1990, the rain gages were improved again to allow instantaneous
rainfall readings that is, a data point is recorded at each tip of the
bucket (0.01 inch of precipitation).
One solar radiometer, located on a regenerated
south-facing clearcut unit in the middle fork of Caspar Creek near the
Eagle subwatershed unit, has been operational for 10 years.
Solar radiation was also monitored along the main stem of the
North Fork in conjunction with the stream biology study (Bottorff
and Knight 1996) to help assess the effects of logging on the
stream community related to increased light. Eight solar radiometers
were installed along a 100-m reach during a study of aquatic insects.
At other sites, photographs of the effective canopy cover have
been taken using a fisheye lens.
Air and water temperatures have been recorded at 0.5-hr or
1-hr intervals at 11 sites beginning in 1988.
Streamflow and Suspended Sediment Measurements
Parshall flumes were chosen as the primary gaging design
to measure streamflow and sediment in the tributary watersheds.
This design has the advantage of allowing sediment to pass through
the gaging station unobstructed and is engineered so that
little calibration is required to calculate streamflow from stage
readings. The design of the floor and side-wall keeps most of the sediment
in suspension so that it can be sampled using pumping samplers.
The flumes were custom-sized to handle the expected range of
discharge in each subwatershed. They were constructed from
old-growth redwood lumber that was milled at the CDF/CDC Parlin
Fork Conservation Camp and pre-fabricated at the
CDF/CDC Chamberlain Creek Conservation Camp cabinet shop. The
flume components were hand-carried to each designated gaging
location, reassembled, and installed on site.
For those subwatersheds that were too large to
feasibly construct and install an appropriately-sized Parshall flume,
natural channel-bottom rated sections were installed. These consisted
of parallel plywood sidewalls erected on each side of the channel
and sized for the expected range of stream discharge.
Discharge measurements were required at these stations to establish
and periodically update the relationship between water height
(stage) and discharge.
Four stream gages (ARF, FLY, IVE, and LAN) were
operational by November 1983. Four more stations (DOL, EAG, GIB, and
HEN) were fully operational by the following November. The
four remaining stations (BAN, CAR, JOH, and KJE) were not
operational until January 1985, because of delays in acquiring the
necessary equipment. An additional control station (MUN) was completed
in September 1985. Because of the scattered start-up times and
the time required to install and troubleshoot new sampling
technology, most of the analyses begin with hydrologic year 1986.
Sampling Development and Design
Critical to the success of obtaining unbiased estimates of
suspended sediment loads at these remote sites were the development
and implementation of a new sampling technology. In these
small forested watersheds, high-discharge flows occur
relatively infrequently, but carry a disproportionate part of the
sediment. Traditional methods of sampling suspended sediment give
biased estimates of total sediment yield and do not allow valid
estimation of error (Thomas 1980). SALT (Selection At List Time) and
related methods had been in use in forest sampling (e.g., 3P cruising)
for many years, but research statistician Robert Thomas
successfully modified the method for use in sampling suspended sediment
loads (Thomas 1985).
SALT Sampling Hardware and Process
The initial station equipment (fig. 1) consisted of a 12-volt
battery-powered system that included portable computer, interface
circuit board, pressure transducer, ISCO pumping sampler, and a
backup stage chart-recorder with an event marker (Eads 1987).
Figure 1- Station equipment setup.
RSL (PSW Redwood Sciences Laboratory) also designed
an interface circuit board that could convert input data from a
stage-sensing device the pressure transducer (fig.
2) and also produce an output signal to the pumping sampler to collect
a pumped sample. The electronic data storage and transfer
functions eventually used a more powerful portable computer the
HP-71B that the field crews carried with them. The data were archived
on other media and sent via modem to the mainframe computer at
the Redwood Sciences Laboratory.
Figure 2- Stage sensing device.
Staffing requirements were high for equipment
maintenance and data retrieval even with the sophisticated sampling
schemes. During the full-scale monitoring period, up to 16 people might
be involved in alternating 12-hour shifts during storm periods.
The watershed was divided into sections and 3 to 4 two-person
crews would cover their assigned stations, retrieving data from
the computers and replacing the full sample bottles.
Troubleshooting was an important function to ensure that the system was
working properly. Corrosion of terminals, low voltages, and clogged
intakes were some of the common problems that had to be dealt
with immediately to minimize the loss of data during these
important storm flow periods.
The long-term monitoring phase of the study began in water
year 1996 and ushered in a new sampling scheme that relies on
real-time turbidity data to drive the sampling process. Experience has
shown that the excellent relationship between suspended sediment
and turbidity can reduce the sampling effort considerably (Lewis
1996). Results have shown that the relationship between
sediment concentration and turbidity has been generally linear and has
little scatter for a given station and storm. The current
turbidity-based sampling system collects in-stream turbidity measurements
every 10 min at eight stations. This approach has reduced the number
of samples to about one-sixth of the number needed under a
SALT sampling regime.
The first harvest entry into the North Fork watershed occurred
in spring 1985 (Preface, fig. 2, these proceedings). The Caspar West
85 timber sale was located in a subwatershed just upstream from
the North Fork weir. About 64 ha, spread over two units, were
harvested in this sale. More than 90 percent of the area was clearcut with
the remaining area being selectively cut stream buffers. About 52
ha were cable logged and 12 ha were tractor logged near
ridgetops. Nearly 2 km of new haul road were constructed near the ridgetop
as part of this sale, primarily to provide cable-yarding access.
This area was logged independently of the CWE timber sales.
Initial information about this area had indicated that the soils were
not similar to the rest of the watershed. However, later
investigation indicated otherwise.
After about 4 years of pretreatment stream monitoring,
harvesting activities began in the North Fork CWE study area
(table 1). Felling began in spring 1989 on the Caspar East Timber Sale the first
of three timber sales planned as part of this study phase. The
upper three units (J, L, and K) were logged as part of this sale. A
steady progression of harvest-related activities allowed the completion
of this first sale by spring 1990 (table 1). Two units of the sale (J and
L) were broadcast burned in fall 1990 to reduce the fuel loading and
to accommodate replanting.
To investigate the effects of burning on sedimentation, units
E and G were burned in the fall/winter period after harvesting
was completed. Units C and K were designated non-burn units.
The second sale in the series was the 79-ha Rice 1990. This
sale covered the middle third of the North Fork watershed in
three separate clearcut units (E, G, and V). Felling for road
construction began in April 1990. An unexpectedly large amount of
precipitation in late May (more than 12 inches) affected some of the new
road construction in and between units E and V, although no
significant off-site impacts were detected. A small portion of unit V was
yarded downhill. This is an unusual practice and was the only place
where this occurred.
Tramway 1991 was the final and most downstream sale in
the series. The sale was named after the historic tramway
mentioned earlier in this paper. Remnants of this railway incline were
protected as a documented archeological feature and are still visible
today. Two of the clearcut subwatersheds (G and C) shared a
divide, technically producing a cut unit larger than that allowed
under Forest Practice Rules. The experiment required implementation
of this sale design, so ultimately the timber harvest was
permitted through a CEQA process and the Board of Forestry declared
the North Fork an official experimental watershed. This sale was
done very quickly, having started in September 1991 and completed
by January 1992.
Table 2 shows how the subwatersheds were affected by
the harvesting activities. The largest subwatershed, ARF, just above
the North Fork weir, for example, had just over one third of its area
affected by cable yarding and less than 10 percent affected by tractor
logging. About one percent of this watershed is in new roads, and the total
bare area created by new roads, landings, and skid trails is about 3
percent. About one quarter of the watershed area above station ARF was burned.
Other Studies or Treatments
Organic Step Mapping Study
This study was initiated to determine the mobility and dynamics
of organic steps and debris within the main-stem and tributaries
of the North Fork. Results will be used to estimate the availability
of sediment storage sites and the buffering capability of
channels following management activities.
The main-stem channel system had been mapped in 1984 at
a scale of 1:500, whereas the tributaries were mapped at 1:250.
Bank characteristics, gravel bars, rock outcroppings, and live and
dead organic material were mapped. Each organic step (debris
dam) having a minimum height of one foot and storing a sediment
volume of at least 5 cubic feet is mapped and assigned a number
and condition rating. Channels have been remeasured annually
during the summer low-flow period.
Large Event Survey
An important sediment contribution to the channel can be
large erosion features that most often occur during storms.
Erosion events exceeding 10 cubic yards were surveyed after most storms.
A sketch is made of each landslide, and its location is identified on
the detailed watershed map.
A study of subsurface drainage patterns before and after
logging was initiated in a 0.81-ha portion of a swale in the K unit in
1987. Piezometers were installed to bedrock in multiple locations
with depths varying from 1.5 to 8 m. Tensiometers were placed at 1.2
m and 1.5 m depths. The instruments were placed along five
separate hillslope segments having straight, concave, and convex
contours (Keppeler and others 1994).
Table 2-Percentage of each subwatershed affected by various treatments.
Quantitative information on bedload rates and patterns
of movement is an important addition to the overall knowledge
about sedimentation effects from harvest activities. One objective of
this study was to refine and calibrate a bedload measurement
technique for use in small to medium-sized forested catchments with
flashy hydrographs (Albright and others 1987). The
Birkbeck-type sampler consists of a cast concrete form (pit), 0.6 m on a side, with
a removable top cover that is horizontally level with the stream
bed. Removable metal boxes inside the concrete forms collect
the bedload material that passes through a 0.1-m-wide slot. Four
of these pits were installed at Station ARF. Bedload transport
rates were initially monitored by a hydraulic system using a
pressure transducer to sense pressure in a fluid-filled pillow and a data
logger to record the pressure. Each pressure pillow and transducer
were soon replaced by a load cell that produces a voltage that,
when interrogated by the data logger, is proportional to the
submerged weight of the box (Lewis 1991). Collected material was
removed after each storm. A fixed I-beam was used for winching the
full boxes from the concrete pits. A sump pump was used to empty
the boxes during a storm. Some of this bedload material was sieved
for grain-size analysis. For a measure of total annual bedload,
detailed surveys of the bedload delta at the upper end of the North
Fork debris basin were completed each year from 1989 to 1995.
Low Flow Study
Much of the summer low flow in the tributaries is
subsurface through porous gravel. To measure summer low flow,
slotted polyvinylchloride (PVC) pipes were buried in the streambed with
a pressure transducer that was interrogated periodically by an
HP-71B data logger (Keppeler 1986).
Aquatic Invertebrate Biological Studies
The objective of the North Fork Caspar Creek biological study
was to determine whether logging treatments (1989-1991) within
the drainage basin caused changes in three components of
stream structure and function: (1) the benthic
macroinvertebrate community; (2) leaf litter processing rates; and (3) the benthic
algal community (Bottorff and Knight 1996).
Water Chemistry and Quality
The primary purpose of this research was to examine the effects
of forest harvest and post-harvest management practices
on biogeochemical processes. Results provide information
to understand the complex interactions that occur in nutrient
cycling processes at the ecosystem scale (Dahlgren 1998).
Aquatic Vertebrate Biological Studies
Since the mid-1980's, fisheries research has been examining
the relationships between timber harvest, aquatic habitat,
and vertebrate populations.
Two flights have been made over the Caspar watershed to
produce large-scale (1:6000) color photographs of the study area. The
first was completed in summer 1988 to document the
watershed condition before harvest. The second flight was completed
in summer 1992 to document the condition of the logged
watershed. These aerial photos were used in timber sale planning and, later,
in geomorphic mapping both the North and South Forks.
Vegetation Management Treatments
Although not part of the initial study design, several types
of vegetation management treatments were applied to a number
of units at various times. To reduce the competition from both
native and exotic plant invaders, herbicide applications were used in
units J, G, E, and V. The chemicals have all been applied with
hand-operated backpack sprayers using either a directed-broadcast or
a directed-spot treatment. A one percent formulation of Garlon
4 herbicide was used in these two types of application.
Precommercial thinning has also been used, although, to date, only in units Y and
Z as part of the 1985 Caspar West timber sale. The other cut units
are planned to receive these treatments as needed to foster
rapid regrowth of commercially-desirable forest vegetation.
Albright, J.S.; Lisle, T.E.; Thomas R.B. 1987.
Measurement of bedload pattern and rates in a small coastal stream in northwestern
California. Unpubl. study plan. Arcata, CA: Redwood Sciences Laboratory, Pacific Southwest Forest and
Range Experiment Station, Forest Service, U.S. Department of Agriculture; 5 p.
Anonymous. 1964. Second progress report 1963-64, Cooperative
watershed management in the lower conifer zone of
California. Berkeley, CA: Pacific Southwest Forest and Range Experiment Station, Forest Service,
U.S. Department of Agriculture; 19 p.
Bottorff, R.L.; Knight, A.W. 1996. The effects of clearcut logging on stream
biology of the North Fork of Caspar Creek, Jackson Demonstration State
Forest, Fort Bragg, CA1986 to 1994. Unpubl. Final Rept. prepared for the Calif. Dept.
of Forestry and Fire Protection, Contract No. 8CA3802. Sacramento, CA. 177 p.
Dahlgren, R.A. 1998. Effects of forest harvest on biogeochemical processes in
the Caspar Creek Watershed. Unpubl. Draft Final Rept. prepared for the
Calif. Dept. of Forestry and Fire Protection. Contract No. 8CA17039.
Sacramento, CA. 151 p.
Eads, R.E. 1987. Instrumenting and operating SALT: A training manual, Section
1. Unpubl. manual. Arcata, CA: Redwood Sciences Laboratory, Pacific
Southwest Forest and Range Experiment Station, Forest Service, U.S. Department
of Agriculture; 33 p.
Kabel, C.S.; German, E.R. 1967. Caspar Creek study completion
report. Marine Resources Branch Administrative Report No. 67-4. Sacramento CA:
The Resources Agency, Calif. Dept. of Fish and Game; 27 p.
Keppeler, E.T. 1986. The effects of selective logging on low flows and water yield
in a coastal stream in northern California. Arcata, CA: Humboldt State
University; 137 p. M.S. thesis.
Keppeler, E.T.; Ziemer, Robert R.; Cafferata, P.H. 1994.
Changes in soil moisture and pore pressure after harvesting a forested hillslope in northern
California. In: Marston, R.A.; Hasfurther, V.R., eds. Effects of human-induced changes
on hydrologic systems; 1994 June 26-29; Jackson Hole, WY. Herndon,
VA: American Water Resources Association; 205-214.
Krammes, J.S.; Burns, D.M. 1973. Road construction on Caspar Creek
watersheds a 10-year progress report. Res. Paper PSW-93. Berkeley, CA:
Pacific Southwest Forest and Range Experiment Station, Forest Service,
U.S. Department of Agriculture; 10 p.
Lewis, J. 1991. An improved bedload
sampler. In: Fan, S.; Kuo, Y.H., eds. Fifth Federal Interagency Sedimentation Conference Proceedings; 1991 March
18-21; Las Vegas, NV. Washington, DC: Federal Energy Regulatory
Commission; 6-1 to 6-8.
Lewis, J. 1996. Turbidity-controlled suspended sediment sampling for
runoff-event load estimation. Water Resources Research 32(7): 2299-2310.
Napolitano, M.B. 1996. Sediment transport and storage in North Fork
Caspar Creek, Mendocino County, California: water years
1980-1988. Arcata, CA: Humboldt State University; 148 p. M.S. thesis.
Rice, R.M. 1983. Caspar Creek Study, Supplement 1 The effects of
combined cable/tractor logging on the sediment regime and on total water and
sediment output. Study 3.152 Caspar Creek Sediment Routing, Phase 1:
Preliminary Reconnaissance Plan. Unpubl. study plan. Arcata, CA: Redwood
Sciences Laboratory, Pacific Southwest Forest and Range Experiment Station,
Forest Service, U.S. Department of Agriculture; 13 p.
Thomas, R.B. 1980. Caspar Creek Study, Supplement 1 The Effects of
combined cable/tractor logging on the sediment regime and on total water and
sediment output. FS-PSW-1651. Unpubl. study plan. Arcata, CA: Redwood
Sciences Laboratory, Pacific Southwest Forest and Range Experiment Station,
Forest Service, U.S. Department of Agriculture; 16 p.
Thomas, R.B. 1985. Estimating total suspended sediment yield with
probability sampling. Water Resources Research 21(9): 1381-1388.
Tilley, F.B.; Rice, R.M. 1977. Caspar Creek watershed studya current
status report. State Forest Notes No. 66. Sacramento, CA: State of Calif.,
Department of Forestry; 15 p.
Wosika, Edward Pearson. 1981. Hydrologic properties of one major and two
minor soil series of the Coast Ranges of northern
California. Arcata, CA: Humboldt State University; 150 p. M.S. thesis.
Wright, Kenneth A. 1985. Changes in storm hydrographs after roadbuilding
and selective logging on a coastal watershed in northern
California. Arcata, CA: Humboldt State University; 55 p. M.S. thesis.
Ziemer, R. 1996. Caspar Creek streamflow and sediment records:
1963-1995. CD-ROM, 200 MB. 1996 July. Arcata, CA: Pacific Southwest Research
Station, Forest Service, U.S. Department of Agriculture, and Fort Bragg, CA:
California Department of Forestry and Fire Protection.