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Author: Robert Dennis Harr
Publisher:
ISBN:
Category : Hydrology
Languages : en
Pages : 20
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Book Description
The hydrology of small forest streams in western Oregon varies by time and space in terms of both streamflow and channel hydraulics. Overland flow rarely occurs on undisturbed soils. Instead, water is transmitted rapidly through soils to stream channels by displacement of stored soil water. Drainage networks expand and contract according to the interaction between precipitation characteristics and soil's capability to store and transmit water. Drainage networks are more extensive in winter than in summer. Streamflow may he 1,000 to 5,000 times greater during winter storms than during summer low flow. A stream's kinetic energy varies along with streamflow. Channel width and depth, heterogeneity of bed materials, and the accumulation of large, organic debris affects the dissipation of kinetic energy. Clearcutting can increase relatively small peak flows, but forest roads and extensive areas of soil compacted by other means may increase larger peak flows. Both roadbuilding and clearcutting can cause soil mass movements, which can drastically alter a stream's channel hydraulics by adding debris or scouring the charnel to bedrock. Removal of naturally occurring organic debris that has become part of a stable channel can accelerate bed and bank erosion.
Author: Robert Dennis Harr
Publisher:
ISBN:
Category : Hydrology
Languages : en
Pages : 20
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Book Description
The hydrology of small forest streams in western Oregon varies by time and space in terms of both streamflow and channel hydraulics. Overland flow rarely occurs on undisturbed soils. Instead, water is transmitted rapidly through soils to stream channels by displacement of stored soil water. Drainage networks expand and contract according to the interaction between precipitation characteristics and soil's capability to store and transmit water. Drainage networks are more extensive in winter than in summer. Streamflow may he 1,000 to 5,000 times greater during winter storms than during summer low flow. A stream's kinetic energy varies along with streamflow. Channel width and depth, heterogeneity of bed materials, and the accumulation of large, organic debris affects the dissipation of kinetic energy. Clearcutting can increase relatively small peak flows, but forest roads and extensive areas of soil compacted by other means may increase larger peak flows. Both roadbuilding and clearcutting can cause soil mass movements, which can drastically alter a stream's channel hydraulics by adding debris or scouring the charnel to bedrock. Removal of naturally occurring organic debris that has become part of a stable channel can accelerate bed and bank erosion.
Author: R. Dennis Harr
Publisher:
ISBN:
Category : Hydrology
Languages : en
Pages : 15
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Book Description
Author: Robert Dennis Harr
Publisher:
ISBN:
Category : Forest roads
Languages : en
Pages : 24
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Book Description
Forest management activities, including roadbuilding, clearcut logging, and broadcast burning, can change certain portions of the forest hydrologic cycle. Watershed studies and other hydrologic research in the Coast and western Cascade Ranges of Oregon have shown that these changes may increase annual water yield up to 62 centimeters, double minimum flows in summer, and increase fall peak flows up to 200 percent and small winter peak flows up to 45 percent in small watersheds. Changes in streamflow resulting from clearcut logging had little effect on either onsite damage to stream channels and hydraulic structures or downstream flooding when yarding caused only light disturbance of soil. By increasing the size of larger peak flows, roadbuilding and soil compaction may cause onsite damage in small, headwater basins. Increases in annual yield and minimum flows may be substantial on small watersheds that are clearcut; under sustained yield forest management, such increases are masked in large, parent watersheds by unaltered streamflow from unlogged watersheds.
Author: R. Dennis Harr
Publisher:
ISBN:
Category :
Languages : en
Pages : 15
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Book Description
Author: Gordon Grant
Publisher:
ISBN:
Category : Forest hydrology
Languages : en
Pages : 86
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Book Description
This is a state-of-the-science synthesis of the effects of forest harvest activities on peak flows and channel morphology in the Pacific Northwest, with a specific focus on western Oregon and Washington. We develop a database of relevant studies reporting peak flow data across rain-, transient-, and snow-dominated hydrologic zones, and provide a quantitative comparison of changes in peak flow across both a range of flows and forest practices. Increases in peak flows generally diminish with decreasing intensity of percentage of watershed harvested and lengthening recurrence intervals of flow. Watersheds located in the rain-dominated zone appear to be less sensitive to peak flow changes than those in the transient snow zone; insufficient data limit interpretations for the snow zone. Where present, peak flow effects on channel morphology should be confined to stream reaches where channel gradients are less than approximately 0.02 and streambeds are composed of gravel and finer material. We provide guidance as to how managers might evaluate the potential risk of peak flow increases based on factors such as presence of roads, watershed drainage efficiency, and specific management treatments employed. The magnitude of effects of forest harvest on peak flows in the Pacific Northwest, as represented by the data reported here, are relatively minor in comparison to other anthropogenic changes to streams and watersheds.
Author: Gordon E. Grant
Publisher: DIANE Publishing
ISBN: 1437927130
Category : Nature
Languages : en
Pages : 84
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Book Description
Includes a database of relevant studies reporting peak flow data across rain-, transient-, and snow-dominated hydrologic zones. Provides a quantitative comparison of changes in peak flow across both a range of flows and forest practices. Increases in peak flows generally diminish with decreasing intensity of percentage of watershed harvested and lengthening recurrence intervals of flow. Peak flow effects on channel morphology should be confined to stream reaches where channel gradients are less than 0.02 and streambeds are composed of gravel and finer material. Managers should evaluate the potential risk of peak flow increases based on factors such as presence of roads, specific mgmt. treatments employed, and watershed drainage efficiency.
Author: Frederick John Swanson
Publisher:
ISBN:
Category : Organic water pollutants
Languages : en
Pages : 24
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Book Description
"Large organic debris has historically been an important element in small mountain streams of the Pacific Northwest. The debris serves to slow the movement of water and inorganic and fine organic matter through the channel. Debris may remain in the channel for decades or longer, and tends to stabilize some sections of a streambed and stream banks while destabilizing other areas. The combination of clear cutting and the complete removal of large debris in a channel may deprive a stream of this natural feature of streams for a century or longer. The consequences are likely to be downcutting and channelization" of the stream, accelerated transport of fine organic and inorganic sediment, and a possible decrease in biological productivity of the stream ecosystem. Therefore, stream debris management during logging operations should include leaving undisturbed the natural, stable organic debris in the channel.??The principal factors controlling the concentration, stability, and functions of stream debris are the history and condition of the surrounding timber stand, flushing history of the channel, stability and abundance of bedload material, steepness of the channel and adjacent hillslopes, and slope stability in the drainage. Because of this complexity, each stream presents a unique situation, which should be inspected in the field and considered on an individual basis before a debris management decision is made."
Author: Daniel T. Snyder
Publisher:
ISBN:
Category : Hydrogeology
Languages : en
Pages : 60
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Book Description
Author: John D. Stednick
Publisher: Springer Science & Business Media
ISBN: 0387690360
Category : Technology & Engineering
Languages : en
Pages : 321
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Book Description
The Alsea Logging and Aquatic Resources Study, commissioned by the Oregon Legislature in 1959, marked the beginning of four decades of research in the Pacific Northwest devoted to understanding the impacts of forest practices on water quality, water quantity, aquatic habitat, and aquatic organism popu- tions. While earlier watershed research examined changes in runoff and erosion from various land uses, this study was the first watershed experiment to focus so heavily on aquatic habitat and organism response to forest practices. The Alsea Watershed Study, as it came to be known, extended over 15 years with seven years of pretreatment calibration measurements, a year of treatment, and seven years of post-treatment monitoring. The research was a cooperative effort with scientists from Oregon State University, Oregon Department of Fish and Wildlife, the U.S. Geological Survey, and the U.S. Environmental Protection Agency. Cooperating landowners included the Georgia-Pacific Corporation, the U.S. Forest Service, and a local rancher. It was a remarkable 15-year partnership marked by excellent cooperation among the participants and outstanding coordination among the scientists, many of whom participated actively for the entire period.
Author:
Publisher:
ISBN:
Category : Hydrology
Languages : en
Pages : 444
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Book Description
