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PROJECTS > Mountain Creek

Mountain Creek Habitat – Irrigation

Location

mitchell-or

Mitchell, OR

Total Cost

$1,700,000

Project Partners

  • Landowners (2)
  • Oregon Watershed Enhancement Board
  • U. S. Fish and Wildlife Service
  • Oregon Department of Fish and Wildlife
  • Wheeler Soil and Water Conservation District
  • Confederated Tribes of the Warm Springs
  • Natural Resource Conservation Service
  • Bonneville Power Administration

Project Elements

  • Flood Control
  • Historic Channel Reactivation
  • Large Wood Placement
  • Floodplain Reactivation
  • Bridge Installation
  • Riparian Fencing
  • Riparian Planting
  • Bank Stabilization

RSI Involvement

  • Funding Acquisition
  • Hydraulic and Hydrologic Modeling
  • In-stream and Bridge Survey and Design
  • Permitting
  • Riparian Planting Implementation
  • Partners Coordination

Panoramic view of a side-channel reaction with large woody debris placement.

Aerial view of stream reach constructed in 2013 and first year after flow reintroduction.

Riffle constructed in 2010 to raise the stream elevation for better floodplain connectivity. RSI staff can be seen performing flow monitoring work (2016) as part of the project’s long term effectiveness monitoring.

Bank pull-back and floodplain work.

One of the five bridges installed as part of this project.

The finished structure. The “saw toothed” full round weir controls flow down the bypass channel which acts as an emergency high flow release and allows for a quick increase in stream flow once flood stage has been reached. The fish ladder is to ensure that fish entrapment will not occur once the channel is activated. The sill on the river right side of the structure is the entrance to the historic channel.

Sill being placed by a boom-truck.

RSI staff assisting the John Day ODFW Screenshop in the pouring of the 50 cubic yard footer for the structure.

Project Description

This project was a multi-year multi-phase endeavor with the end goal of re-engaging 3.5 miles of historic channel of Mountain Creek and improving the landowner’s ability to irrigate 300 acres of meadow fields. The stream had been diverted into a bypass channel to avoid flooding issues in the low meadow areas but over time had created an incised channel that de-watered during the summer months with the sub-surface flow migrating back into the historic channel effectively creating a passage barrier to all aquatic species. Hydraulic and hydrologic modeling was used to develop inundation levels and determine maximum allowable flow through the historic channel. The irrigation system incorporated 36,000 ft of PVC irrigation pipeline with multiple control valves and spurlines to allow for efficient flood irrigation of the meadow fields. All phases of this project were completed within budget.

All four phases of the project included stream restoration and habitat creation which include; large wood placement, bank pullbacks, side-channel activation, and bridge installation. The landowner did the bulk of the work as his in-kind. RSI coordinated closely with the landowner on the construction and the resulting work has been toured and filmed by multiple agencies including USFWS.

The reactivation of the 3.5 miles of historic channel was accomplished in the summer of 2015. To alleviate the landowner’s concern that the re-engaged channel would create flooding issues, a structure was placed at the diversion point to divert water from the bypass channel into the historic channel. This structure allowed excess flow to be directed down the bypass channel during high flow events, but during normal operation the entirety of the flow will be directed down the historic channel. RSI was responsible for the design and modeling of the structure. Given the site constraints and the landowner concerns, RSI was required to design a complex structure that would allow a disproportionate amount of the high flow event to use the bypass channel and as such limit the amount of flow the landowner’s infrastructure would experience at higher events. This resulted in a complex dual weir design with a fish passage ladder incorporated into the structure.

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