Tucannon River Off-Set Dike Construction

Columbia Conservation District (CCD) increased floodplain connectivity and riparian function on approximately 130 acres by setting back existing levees along 3.2 miles of the Tucannon River. Partial funds were available in 2009 to initiate preliminary construction tasks, including modifying an existing irrigation pivot, removing a grain silo, installing a new pivot, and site prep. A cost increase in 2010 completed those and all remaining tasks, including breaching/removing the existing levee, constructing sections of setback levee where needed, and riparian restoration. The project also provided support for auxiliary stream protection projects, including 5 off-site watering facilities that allowed removal of livestock from the riparian area where they had direct access to the river. Improved floodplain connectivity and riparian function provided by the project is intended to increase the quantity and quality of spawning, resting and rearing habitat for three Endangered Species Act-listed fish in this reach (spring Chinook, steelhead and bull trout). It also provides opportunity for the river channel to meander, dissipate high river flow and velocity, increase water storage, and moderate substrate transport.

The project represents the culmination of the CCD’s long-term program to work with landowners to restore functioning river habitats, while allowing for productive agricultural use of adjoining lands. The CCD worked with 5 landowners to finalize the dike setback assessment and design (SRFB #09-1742). Final designs were provided for review and approval by the RCO prior to construction. Project implementation funds included in-kind donations by landowners and additional grant funds from the Bonneville Power Administration (BPA), Washington State Conservation Commission (WSCC), Washington Department of Ecology (WDOE) and Water Resource Inventory Area 35 (WRIA 35).

Off-set dike modification and installation began with cultural resource surveys, obtaining permits, environmental concurrences, removal of a silo, fence removal, installation of one pivot system and the modification of another pivot. These preliminary activities allowed for 3.2 miles of off-set dike construction to occur during the winter of 2011/2012. Following construction, 30 acres of grass re-seeding and planting of 6,500 trees and shrubs occurred. Spring 2012 also saw the start of fence rebuilding and construction of new fence to limit livestock access to the riparian and river. Fencing continued through winter 2013/2014 with total footage of 11,597 ft. (2.20 miles). Fall 2012 required some point-bar shaping and re-seeding to modify an eroding condition resulting from the previous year’s dike building. Five (5) off-site water systems were built to facilitate livestock removal from the newly reconnected floodplain and riparian and instream habitat. Three (3) of the systems are solar powered. Final work in fall and winter 2013/2014 included completing fence installation, planting 3,000 additional trees and shrubs, and repairing access roads.

The total $842,221.60 project cost was provided by RCO ($464,028.87), Landowners ($95,107.25), Bonneville Power Adminstration ($206,636.01), Washington State Conservation Commission ($12,640.75), Dept of Ecology ($31,808.72), and WRIA 35 ($32,000.00).

The goal of the project was to restore floodplain connectivity and improve riparian function to create a place for spawning, resting and rearing for three Endangered Species Act-listed fish in this reach (spring Chinook, steelhead and bull trout). Work also created a place for the river channel to meander, dissipate the rivers flow and velocity, increase water storage and moderate substrate transport.