Introduction and Background - Catherine Creek is critical habitat for ESA listed Snake River summer steelhead, spring Chinook and bull trout as well as resident rainbow and other native fish.  This reach of Catherine Creek is a migration corridor and provides juvenile winter rearing habitat.  Lower Catherine Creek historically meandered a great deal in the reaches above what is now the confluence with the Grande Ronde River.  This channel actually used to be the Grande Ronde River before the construction of the State Ditch in the late 1800’s. Over the years some channel reaches were naturally cutoff, creating oxbows.  Many reaches were intentionally cutoff throughout the early and mid-1900’s with the same result.  Levee construction to protect agricultural lands was also a common practice.  Most often levees were constructed immediately adjacent to the stream channels disconnecting riparian habitats and the stream channel.  The project proposes to create seasonal wetland habitat and salmonid rearing habitat adjacent to lower Catherine Creek by relocating a dike and opening up an oxbow.

Existing Condition - Historically the Grande Ronde River flowed through this reach of Catherine Creek.  In the 1870’s the State Ditch was constructed to cut off a large segment of the Grande Ronde River with the intent of developing agricultural lands and reducing flooding.  Since that time Catherine Creek has flowed through this channel.  Approximately 50 years ago a two hundred foot channel was dug to short-cut about 2000 feet of Catherine Creek.  The old channel was plugged at the upper end but left open at the lower end. Over the years the lower end of the oxbow has silted in, cutting off the oxbow from the main channel during low-flow periods.  At about the same time a levee was constructed along the east side of the oxbow and the live channel. Water backs up into the oxbow during periods of high flow.

The project proposes to improve habitat for ESA-listed species by increasing habitat quantity and improving habitat diversity.

Specific Objectives are:
• Increase quality and quantity of off-channel salmonid rearing habitat by reactivating about 2000 feet old stream channel
• Increase water storage for late season release (potential late-season flow increase and temperature decrease)
• Restore connectivity between stream channel and adjacent landscape
• Improve habitat for wetland and riparian-dependent species

Proposed Actions:
• Remove approximately 2000 feet of the existing dike adjacent to the Catherine Creek channel and the oxbow
• Construct approximately 2500 feet of a new dike 50-250 feet back from the stream channel  
• Excavate material within the new flood zone to create more permanent wetlands (ingress and egress provided back to the channel) as per designs
• Remove existing water control structures in the old dike (concrete and headgates)
• Open bottom end of oxbow by removing sediment buildup in the lower approximate 500 feet of the oxbow channel
• Install a 48”culvert through the channel plug at the upper end of the oxbow (free flowing, no headgate)
• Erosion seed disturbed ground with native shrubs, forbs and grasses

Benefits - Juvenile steelhead and Chinook will have access to an additional 2000 feet of the oxbow for winter rearing habitat and off-channel refuge during high flows.  Habitat diversity in the channel will be maintained by providing only minimal flow through the oxbow and not converting it to the main channel.   The additional approximate 6 acres of seasonally flooded ground will promote the establishment of riparian vegetation, increase water storage in the soil profile and improve the connectivity between the stream channel and adjacent landscape.  The additional 6 acres of non-cropped land will provide habitat for many riparian as well as upland species.  This habitat is limited in the intensive agricultural lands along lower Catherine Creek.

Project Maintenance - The project should require very limited maintenance once vegetation becomes established. During vegetation establishment, and periodically thereafter, the landowners will monitor and control noxious weeds.