Understory

Forest harvesting has been shown to cause various changes in water quantity and water quality parameters, highlighting the need for comprehensive forest practice rules. Studies show a myriad of impacts to ecosystems as a result of watershed level changes, such as forest harvesting. Being able to better understand the impact that forest harvesting can have on stream temperature is especially critical in locations where federally threatened or endangered fish species are located. The overall goal of this research project is to assess responses in stream temperature to various riparian and forest...

We explored discharge-suspended sediment relationships in 71 watersheds within nine larger basins in the North Coast of California. These watersheds are highly influenced by their tectonic setting and have a long history of timber harvest activity. We summarized these relationships by generated sediment rating curves (SRC) taking the form of a power function in log-log space: SSC = aQb. Where SSC represents suspended sediment concentration and Q represents normalized discharge. The rating parameters a and b define the vertical offset and slope of the relationship, respectively. We investigated...

We analyzed data sets from the Caspar Creek Watershed study, with a 55-year comprehensive record of hydrologic regime in two sub-watersheds with different logging treatments, and three separate instream biologic studies conducted since 1990. Long-term data sets of instream biota are rare, and we used them to investigate sediment regime response to forest harvest and extremes in flow regime. Increases in sediment transport after logging were observed in the North Fork during second experiment at Caspar Creek in the 1990’s. Our analysis found turbidities were higher after logging across the rang...

In 2016, the Emerald Fire burned 70 ha (173 acres) near the southwest corner of Lake Tahoe on the ridge between Cascade Lake and Tallac Creek. The occurrence of this fire in an area with two roads and a LIDAR elevation data set provided an opportunity to evaluate the impacts of roads on post wildfire erosion, and to test other postfire erosion modeling tools. This study evaluated road effects on soil erosion in a fire-disturbed forest with GIS technology and a soil erosion model, and the likelihood of mass failure by debris flow, translational failure and dry ravel. Results showed that roads c...

The Caspar Creek Experimental Watershed, located in the Jackson Demonstration State Forest, has been continuously studied since its establishment in 1962 as a collaboration between the California Department of Forestry and Fire Protection (CAL FIRE) and the U.S. Forest Service Pacific Southwest Research Station (PSW). The Caspar Creek Experimental Watershed has conducted thus far, two long-term research experiments. The primary goal of the first two experiments (1962-85, 1985-present) was to understand the effect of timber harvest on streamflow and suspended sediment concentrations in coastal-...

Since their establishment in 1962, the Caspar Creek Experimental Watersheds have provided foresters, land managers, researchers, and citizens with information that has influenced forest management in northwestern California. The primary goal in establishing Caspar Creek was to understand how harvesting timber could affect streamflow and suspended sediment concentrations (SSC). The first experiment (1962-1985) was a classic paired-watershed study undertaken before the implementation of the modern California Forest Practice Rules (FPRs): roads were constructed in the South Fork and 60-70% of the...

Watercourse crossings associated with timber harvesting can produce substantial amounts of stream sediment. To reduce the potential for crossing failures and resulting impacts, the California Forest Practice Rules specify that all constructed or reconstructed permanent watercourse crossings must accommodate the estimated 100- year flow, including debris and sediment.Three methods for making office-based estimates of 100-year recurrence-interval streamflows for ungaged basins are presented: (1) an analytical relationship between storm precipitation, watershed characteristics, and runoff, (2) re...

Fire is an inevitable and ecologically important process that maintains the health of forest ecosystems in the Western United States. A century of fire suppression has increased fuel loads to the point that inevitable wildfires often burn too fast and too hot to be contained, thus overwhelming suppression efforts. In response, national forests in the West are increasingly using large prescribed fires, as well as allowing the moderate spread of unplanned wildfires under favorable conditions, to make forests more resilient to drought, bark beetle outbreaks, and wildfires under extreme conditions...

This report represents the contributions of over 200 researchers, students, and technical experts from academia, private sector organizations, and federal, state, and local agencies who conducted scientific studies for nearly 10 years on projects supported by the SNPLMA Science Program. Their hard work provided the scientific basis to preserve, protect and restore the unique aquatic and terrestrial ecosystems in the Lake Tahoe Basin. Environmental managers from federal, state, and local agencies worked closely with the research community as part of the SNPLMA Science Program. Their leadership ...

Natural and managed rivers throughout the world display a wide range of hydrographs that vary in shape from steep and flashy to gradual and consistent, thus influencing the volume and timing of water available for aquatic ecosystems. Although hydrograph shape is an inherent feature of river systems, relatively few investigations have focused on the influence of flow variability on channel grain sizes and bedload transport, and many uncertainties remain with regard to accurately predicting sediment movement during high-flow events. We explored the effects of hydrograph shape on sediment transpo...