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ARS Home » Pacific West Area » Boise, Idaho » Northwest Watershed Research Center » Research » Publications at this Location » Publication #100390
Title: SEDIMENT YIELD AND HYDROLOGY IN NORTHWESTERN RANGELANDS

Author
item Slaughter, Charles
item Pierson Jr, Frederick

Submitted to: International Journal of Sediment Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/14/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Mountainous rangelands of the Pacific Northwest are highly diverse in geology, topography, local climate, and vegetation. Consequently, runoff and sediment yield from high-relief rangeland watersheds exhibit high spatial and temporal variability. It is not possible to characterize the sediment regime of such watersheds by simple indices or short-term localized measurements. Research is needed to identify and quantify the pathways of sediment from initial detachment to temporary storage (deposition) on slope, floodplain or in channel, and subsequent remobilization and transport through the stream system. The role of extreme hydrologic events in accelerated landscape erosion ,deposition and transport of stored sediment, and interaction with dynamic channel-forming processes in rangeland streams remains inadequately defined. Such information is required to address emerging issues of riparian zone and water quality management in northwestern rangelands, including the regulation of stream quality through Total Maximum Daily Load (TMDL) criteria. It is necessary to better determine landscapes and channels susceptible to treatment to reduce stream sedimentation, and to improve and validate simulation models for management of rangeland catchment/stream systems.

Technical Abstract: Rangeland erosion and sediment production are major concerns in northwestern natural resource management. Seasonal variability in precipitation, streamflow and energy available for sediment mobilization and transport is pronounced in northwestern rangeland catchments; runoff and sediment yield exhibit high spatial and temporal variability. The sediment regime of such watersheds cannot be characterized by simple indices or short-term local measurements. A long-term rangeland experimental watershed demonstrates the need for sustained measurement programs over a range of catchment scale and topographic position, to determine actual patterns and rates of runoff and sediment yield. More research is needed to identify and quantify the pathways of sediment from initial detachment to temporary storage and subsequent remobilization and transport through the stream system. The role of extreme hydrologic events in accelerated landscape erosion, remobilization of stored sediment, and interaction with dynamic channel-forming processes in rangeland streams remains inadequately defined.