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ARS Home » Pacific West Area » Pendleton, Oregon » Soil and Water Conservation Research » Research » Publications at this Location » Publication #114792

Title: NORTH-CENTRAL OREGON DRYLAND CROP RIPARIAN CONSERVATION PROJECT

Author
item Williams, John
item Loiland, James
item Camara, Kelli

Submitted to: American Water Resources Association Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 8/28/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: This paper reports on establishment and evaluation of a Conservation Riparian Enhancement Project (CREP). Riparian areas are vegetation and animal communities found near bodies of water and perennially wet areas. Native riparian areas in dryland crop regions of the intermountain Pacific Northwest have been largely eliminated during the last 140 years. Native riparian grass, shrub, and tree species found on broad flood plains have been replaced by introduced species growing in narrow, incised channels. Landowners 1.5 miles of Gerking Creek, located near Athena, Oregon, are working to reestablish a riparian community in former cropland, known as the Gerking Flat project. To aid in this effort, an evaluation of present conditions and constraints imposed by existing vegetation, channel morphology, and management were quantified. Reestablishment of a riparian community will depend upon changes in upland and channel management. Establishment of a buffer strip between cropland and channel will address excessive sediment delivery from the upland area within the project and the adjoining fields. However, Gerking Creek will continue to be a source of considerable sediment and energy associated with concentrated flow, and stabilization of the channel within the project area might require active construction of a designed channel to effectively handle high energy flows and large sediment loads.

Technical Abstract: Native riparian areas in dryland crop region of the intermountain Pacific Northwest have been largely eliminated during the last 140 years. Native riparian grass, shrub, and tree species found on broad flood plains have been replaced by introduced species growing in narrow, incised channels. Owners of 2.2 km of Gerking Creek, located near Athena, Oregon, are working to reestablish a riparian community in former cropland, known as the Gerking Flat project. This effort requires an evaluation of present conditions and constraints imposed by existing vegetation, channel morphology, and management. We quantified valley bottom landform and channel development, by establishing 22 channel cross-sections and developing a detailed contour map of the site. Reestablishment of a riparian community will depend upon changes in upland and channel management. Establishment of a buffer strip between cropland and channel will address excessive sediment delivery from the upland area within the project and the adjoining fields. However, Gerking Creek will continue to be a source of considerable sediment and energy associated with concentrated flow. Channel adjustment can be expected to continue in the form of deposition, headcut migration, channel migration, and bank sloughing. These processes can tear out newly planted material and alter soil-water relationships in the riparian area. Among the alternatives available for the Gerking Flat Project are (1) to leave the channel within the project area to develop on its own or (2) to design a channel with reduced stream slope, a raised stream bed, and increased meander frequency.