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Lower Cottonwood Creek Points of Diversion Modification Projects

PostConstruction web

Client: Monument Soil and Water Conservation District

Cottonwood Creek is a major tributary to the North Fork John Day River and has been identified as critical habitat for Middle Columbia River steelhead. The lower four miles of the creek enters a broad valley, providing opportunities for agriculture that relies on the water of Cottonwood Creek for production. There are currently 12 diversion sites along lower Cottonwood Creek, referred to as points of diversion (POD’s). Many of these diversions result in fish passage barriers during the low flow season. The Monument Soil and Water Conservation district requested Waterways assistance in the assessment of channel stability and fish passage for all 12 PODs and designs for three of the known fish passage barriers.

 

In response, Waterways conducted a comprehensive evaluation of geomorphic conditions within the lower Cottonwood Creek and prepared an assessment report that identified potential actions to improve fish passage for nine of the PODs and developed engineering drawings for the three barriers. The goals of the proposed modifications were to create a stable section of channel at the POD that provided fish passage while requiring minimal maintenance from irrigators. The design for each of the three fish passage barriers consisted of building roughened channels downstream of the existing diversion infrastructure (sheet pile grade control structures) to create backwatered pools, add log jams at two of the three PODs for habitat complexity, and structural modification of the sheet pile structures to constrict low flows. A total of four POD sites were constructed during the summers of 2014 and 2015.