NORTH-CENTRAL OREGON DRYLAND CROP RIPARIAN CONSERVATION PROJECT

摘要

Native riparian areas in the dryland crop region of the inter-mountain Pacific Northwest have been largely eliminated during the last 140 years. Native riparian grass, shrub, and tree species found on broad floodplains have been replaced by introduced species growing in narrow, incised channels.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. 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.