Treesearch

The effects of road building and timber harvest on storm flow were evaluated at the North and South Forks of Caspar Creek in north coastal California. From 1963 though 1975, a total of 174 storms that produced peak discharges larger than 0.016 Ls-1ha-1 in the untreated North Fork were studied. Storms producing flows this size and larger occur about 14 times each year and about 10 percent of the time. They are responsible for 83 percent of the annual water discharge and transport 99 percent of the suspended sediment.

The Caspar Creek watershed study provides resource professionals with information regarding the impacts of timber operations conducted under varying forest practices on sensitive aquatic habitats. In the South Fork watershed, roads were constructed near watercourse channels in the 1960's, and the watershed was selectively logged using tractors during the early 1970's. Subwatersheds in the North Fork were clearcut from 1985 to 1991 using predominantly cable yarding and roads located high on ridges. Numerous landslides were documented after road construction and logging in the South Fork...

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 degree 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.

The results of every watershed experiment are a unique combination of the site, the weather, the questions asked, the quality of the data produced, and the quality of the analysis made of those data. These results narrow the scope of the environmental debate, but they will not alter the value systems of the debaters. By availing themselves of the available scientific information, both sides can make their cases more persuasive to the courts, to the regulators, and perhaps to the public.

Storm-induced streamflow in forested upland watersheds is linked to rainfall by transient, variably saturated flow through several different flow paths. In the absence of exposed bedrock, shallow flow-restrictive layers, or compacted soil surfaces, virtually all of the infiltrated rainfall reaches the stream as subsurface flow. Subsurface runoff can occur within micropores (voids between soil grains), various types of macropores (structural voids between aggregates, plant and animal-induced biopores), and through fractures in weathered and consolidated bedrock. In addition to generating...

Continuous measurement of streamflow at the Caspar Creek watersheds has led to several analyses of the effects of two harvest methods (selection and clearcut) on summer flows and annual yield. Although all Caspar Creek analyses have indicated an increase in runoff after timber removal, the magnitude and duration of the response depend on the nature and extent of the logging and site preparation, climatic conditions, as well as the definition of the hydrologic parameter at issue. Regression analysis using a calibration period of 1963 to 1971 was used to compare annual yield, summer flow...

Regulations increasingly require monitoring to detect changes caused by land management activities. Successful monitoring requires that objectives be clearly stated. Once objectives are clearly identified, it is important to map out all of the components and links that might affect the issues of concern. For each issue and each component that affects that issue, there are appropriate spatial and temporal scales to consider. These scales are not consistent between and amongst one another. For many issues, unusual events are more important than average conditions. Any short-term monitoring...

Riparian buffer strips are a widely accepted tool for helping to sustain aquatic ecosystems and to protect downstream resources and values in forested areas, but controversy persists over how wide a buffer strip is necessary. The physical integrity of stream channels is expected to be sustained if the characteristics and rates of tree fall along buffered reaches are similar to those in undisturbed forests. Although most tree-fall-related sediment and woody debris inputs to Caspar Creek are generated by trees falling from within a tree's height of the channel, about 30 percent of those tree...

Abstract - These proceedings report on 36 years of research at the Caspar Creek Experimental Watershed, Jackson Demonstration State Forest in northwestern California. The 16 papers include discussions of streamflow, sediment production and routing, stream channel condition, soil moisture and subsurface water, nutrient cycling, aquatic and riparian habitat, streamside buffers, cumulative effects, monitoring. A detailed annotated bibliography of 107 papers from Caspar Creek is included

The response of the mainstem channel of North Fork Caspar Creek to recent logging is examined by time trends in bed load yield, scour and fill at resurveyed cross sections, and the volume and fine-sediment content of pools. Companion papers report that recent logging has increased streamflow during the summer and moderate winter rainfall events, and blowdowns from buffer strips have contributed more large woody debris. Changes in bed load yield were not detected despite a strong correlation between total scour and fill and annual effective discharge, perhaps because changes in stormflows...