USDA Forest Service

Pacific Southwest Research Station

Pacific Southwest
Research Station

800 Buchanan Street
Albany, CA 94710-0011
(510) 883-8830
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Caspar Creek Experimental Watershed

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Water: Caspar Creek Watershed Study


Caspar Creek Experimental Watershed serves as an important research site for evaluating the effects of timber management on streamflow, sedimentation, and erosion in the rainfall-dominated forested watersheds of the northern coast of California. Caspar Creek includes two watersheds with nested sub-basins: the North Fork (NFC, 484 ha) and South Fork (SFC, 424 ha). Begun in 1962 as a cooperative effort between the California Department of Forestry and Fire Protection and the USDA Forest Service's Pacific Southwest Research Station, the project has evolved from a simple paired watershed study into one of the most comprehensive and detailed investigations of its kind. Hydrologic data collected here include streamflow, subsurface pipeflow, piezometric pressure, soil moisture tension, suspended sediment, turbidity, bedload transport, air and water temperature, precipitation, and solar radiation. Channel data include channel cross sections, stream habitat typing, woody debris recruitment and riparian canopy evaluations, sediment storage, and pool condition. Hillslope data include landslide inventories, road evaluations, and vegetative condition. Cooperators have undertaken benthic investigations, aquatic vertebrate and macroinvertebrate sampling, and water chemistry monitoring.


Winters are mild and wet, and summers are moderately cool and dry. About 90 percent of the average annual precipitation of 1,200 mm falls during October through April. Summer coastal fog is common. Snow is rare and rainfall intensities are low.


The soils of the basins are well-drained clay-loams, 1 to 2 m in depth, and are derived from Franciscan graywacke sandstone and weathered, coarse-grained shale of Cretaceous Age. They have high hydraulic conductivities, and subsurface stormflow is rapid, producing saturated areas of only limited extent and duration.


Forest types at Caspar Creek include second-growth mixed conifer, mostly coast redwood, Douglas-fir, western hemlock, and grand fir.

Long-Term Data Bases

There are long-term data bases on stream discharge, precipitation, suspended sediment concentration, turbidity, and solar radiation.

Research, Past and Present

Research at Caspar Creek is designed to study the effects of forest practices on watershed and ecological processes. From 1963 to 1967, both the NFC and SFC watersheds were calibrated prior to treatment. At that time, these watersheds supported a 90-year-old, second-growth, mixed conifer forest dominated by coast redwood and Douglas-fir. From 1967 to 1972, roads were constructed and about two-thirds of the stand volume was selectively harvested and tractor yarded from SFC. From 1985 to 1986, 67 percent of an 87-ha ungauged tributary was clearcut and cable yarded immediately upstream of the North Fork gauging station. Logging began in the main study portion of the NFC in 1989 and ended in 1991. Three tributaries in the NFC were left in an untreated control condition. Postlogging measurements continue in the NFC and SFC watersheds.

Major Research Accomplishments and Effects on Management

The South Fork Caspar Creek selection harvest with tractor yarding (phase 1) showed that:

  • Sediment increased by 335 percent from road building in 1968.
  • Sediment increased by 212 percent from tractor logging following the 1970-73 harvest.
  • Major landslides accounted for most of the sediment production in the SFC after logging; more sediment was made available for transport.
  • SFC road system persisted as the major source of sediment, annual streamflow increased by 15 percent, but larger relative increases occurred during summer low flows; during the late 1960's, the salmonid abundance declined but appeared to return to predisturbance levels after only 2 years.

In the Caspar Creek/North Fork studies of clearcutting and skyline cable logging, annual suspended sediment loads increased by 73 percent in the partially clearcut NFC but by more than 100 percent in the clearcut tributary watersheds. An increase in landslides was not observed post-harvest; rather, increases in sediment loads were correlated to the flow increase, length of intermittent channels logged or burned, and new road construction. In clearcut units, storm peaks increased by as much as 300 percent, but the mean increase was 35 percent. As basin wetness increased, peak flow increases lessened. Return to pretreatment flow conditions appears to be occurring 12 years post-harvest. Debris loading (large-wood) increased along the NFC stream channel in the first few years after logging due to increased windthrow. Channel morphology has become more complex with more debris jams, sediment storage "steps," and greater pool volumes. However, no dramatic changes in the abundance of steelhead, coho, and Pacific giant salamander were attributed to logging.


Researchers from the following organizations have worked on Caspar Creek: California Departments of Forestry and Fire Protection and Fish and Game, National Marine Fisheries Service, California Water Quality Control Board, Stanford University, University of California at Davis, University of California at Berkeley, Chico State University, Humboldt State University, California Polytechnic University, and Oregon State University.

Research Opportunities

Caspar Creek provides long-term, records of basic hydrologic and geomorphic processes spanning the downslope sequence of processes from the tree canopy to third-order channels in two watersheds with 26 nested sub-basins. Large-scale experimentation is planned for timber harvest and watershed restoration. New collaborators from a multitude of disciplines, including hydrology, geomorphology, forestry, meteorology, and aquatic and riparian ecology, are welcomed.


Expanded lodging and laboratory facilities are under construction for the Jackson Learning Center nearby. Caspar Creek offices are located at the Jackson Demonstration State Forest office, 802 N. Main Street, Fort Bragg, CA.

Lat. 39° 22´ 30" N, long. 123° 40´ W

Contact Information

Caspar Creek Experimental Watershed
USDA Forest Service
Pacific Southwest Research Station
Redwood Sciences Laboratory
1700 Bayview Drive
Arcata, CA 95521
Tel: (707) 825-2930

Adams, Mary Beth; Loughry, Linda; Plaugher, Linda, comps. 2004. Experimental Forests and Ranges of the USDA Forest Service. Gen. Tech. Rep. NE-321. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northeastern Research Station. 178 p.

1Information has been updated since original publication.