Latah Soil and Water Conservation District

Corral Creek - Racetrack Reach
Corral Creek - Racetrack Reach
Project Title

Corral Creek Stream and Meadow Restoration: Racetrack Reach

Project Location


Corral Creek, a tributary of the Potlatch River, in Latah County, Idaho

Watershed Information and Limiting Factors


Corral Creek subwatershed is 14,300 acres, approximately 4 percent of the Potlatch River Watershed, and includes predominantly forested and canyon stream types. Corral Creek supports spawning and rearing habitat for ESA-listed threatened steelhead trout (Oncorhynchus mykiss). Limiting factors include: high water temperatures, high flashy stream flows, low summer base flows, lack of complexity in stream composition, migration barriers, and sedimentation (Potlatch River Watershed Management Plan 2007).

Ownership


Private land

Project Supporters


Landowner (access and minimum 20 percent project match)
Bonneville Power Administration
Ecotrust / National Marine Fisheries Service Funding
Idaho Office of Species Conservation / Pacific Coast Salmon Recovery Fund
Idaho Department of Environmental Quality / EPA Clean Water Act Funding

Project Description


Problem: Limiting factors affecting steelhead trout habitat in this reach: high water temperatures, high flashy stream flows, low summer base flows, lack of complexity in stream composition, and sedimentation. Legacy effects of logging and associated construction of railroad spur lines and livestock grazing degraded water quality, impaired meadow recharge, and reduced pool habitat in the watershed above this project site. At the project site, the stream channel was straightened and widened in the early 1900's to accommodate construction of a horse racing track. As a result of the higher velocity of flow in the straightened channel, exit of flow from the meadow is unnaturally accelerated and bed and bank erosion is chronic, reducing downstream water quality. Floodplain connectivity and overland flow are impaired due to the deepened, widened channel and the berm constructed for the racetrack. The channel incision and lack of infiltration contribute to a lowered water table, reducing the extent and quality of the riparian buffer zone vegetation. An earlier restoration effort at this site involved planting riparian plants in 2007, 2008, and 2009. However, of over 4,3000 native riparian woody plants added to the riparian zone at Racetrack Reach, only several hundred survived, even though the same species are well-established in dense corridors along both sides of Corral Creek just upstream, where the channel remains sinuous. Nearly all of a few dozen drier site woody plants survived, providing further confirmation of an artificially depressed water table and the need to treat the channel incision in order to improve the hydrologic processes. Improvement and expansion of spawning and rearing habitat for steelhead trout is a priority in the Potlatch River watershed (Clearwater Subbasin Inventory 2004, Potlatch River Watershed Management Plan 2007). Low flow conditions during rearing, in particular, limit survival of juvenile steelhead in the Potlatch drainage (Bowersox et al 2011).
Solution: Address the limiting factors by returning flow to the sinuous, well-vegetated historic channel to reduce erosion, improve stream composition and shading, and restore meadow hydrology to attenuate flash peak flows, increase recharge, improve summer base flows, and reduce water temperature in pools through groundwater seepage. Restoration involved installation of channel plugs in the incised, straightened channel, both to divert the flow out of the ditch, into the nearby sinuous, shallow historic channel, and to create a series of wetland cells to hold water on-site longer to enhance infiltration and aid in restoration of the meadow's hydrology.

Movement of the flow back into the good-condition historic channel will immediately improve habitat for steelhead trout by reducing flow velocity and erosion, returning access to a reach with pools, overhanging vegetation, stable banks, and the potential for leaf litter and woody debris recruitment to improve channel habitat complexity. The smaller, more sinuous historic channel will increase flooding events, infiltration, and storage and can contribute to longer, cooler base flows to the stream, potentially expanding and prolonging availability of rearing habitat for juvenile steelhead. Minor excavation was done to reconnect flow to the historic channel and to create some small swales to improve hydration of the east portion of the meadow. Livestock crossings were constructed to direct cross-channel movement between the east and west side meadow pastures and to reduce bank trampling. Livestock exclusion fencing prevents access to the historic channel and the wetland cells. Immediately following completion of construction, all disturbed areas were seeded with a diverse mix of native grasses and forbs and mulched with a weed-free pelleted straw mulch. Portions of the channel plugs were covered with salvaged wetland herbaceous sod mats or commercially-sources wetland sod mats. Cuttings were taken from nearby native woody riparian plants and planted along the plugs and connector channels. Woody and herbaceous native plants, along with more cuttings, will be planted in 2014, 2015, and possibly 2016. Photo points to detect changes in height and extent of planted and naturally-recruited woody plants were established in 2013 and survival monitoring plots will be set up in 2014. Vegetation monitoring will continue for several years. Flow monitoring has been collected for several years at a monitoring station a few hundred feet downstream of the project site, and will be used to detect changes in length of flow into the summer season. Groundwater and surface elevation monitoring, to detect changes in meadow hydrologic condition, has been in place in the Racetrack Reach Meadow since November 2011, and will continue for several years. Similar water monitoring has been established and will be continued in other meadow systems throughout the Corral Creek watershed, all of which have been or will be part of stream and meadow restoration projects.

Status


Construction completed in October 2013; revegetation continuing.

References


Bowersox, B., R. Banks, and N. Davids. 2011. Potlatch River steelhead monitoring and evaluation project, Annual Report 2011. Idaho Department of Fish and Game, Lewiston, Idaho. .
https://collaboration.idfg.idaho.gov/FisheriesTechnicalReports/Forms/Allitems.aspx
Clearwater Subbasin Plan. 2004. Prepared by Ecovista for Nez Perce Tribe Watershed Division in cooperation with Clearwater Policy Advisory Committee.
www.nwcouncil.org
Potlatch River Watershed Management Plan. 2007. Prepared by Resource Planning Unlimited for the Latah Soil and Water Conservation District, Moscow, Idaho
www.latahsoil.org/id50.html

 


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Above: Racetrack Reach of Corral Creek. The channel was straightened in the early 1900's to accommodate construction of a horse racing track. Prior to removal of a 220 foot long box culvert in 2007, steelhead migration to the upper Corral Creek system was blocked. Juvenile steelhead were detected in the upper system in 2008.

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Above: Where the channel has not been altered, it remains sinuous, shallow, well-vegetated and flows regularly access the floodplain. This site is just a few hundred feet upstream of the straightened, incised reach of Corral Creek that flows through Racetrack Meadow.

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Above: Looking upstream along the ditch which carried the flow of Corral Creek since the racetrack was constructed (early 1900's). Photo was taken from the south end of Racetrack Meadow just after peak flow in spring 2009. Due to the channel incision, very little of the flow accesses the floodplain, even during high flow event.

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Above: Looking downstream; the channelized reach of Corral Creek is on the left. In high flows, some flow carries into the borrow ditch associated with the racetrack berm (arrow indicates the berm) but doesn't contribute significantly to flow in the historic channel. Note the ongoing, extensive erosion.

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Above: We approached restoration of the Racetrack Reach site in a step-wise fashion, first trying the least expensive alternative, re-planting the appropriate native riparian vegetation. However, the channel incision prevented recharge and drains the system. This lowered water table was confirmed by the low survival of the riparian species, while survival of the driest-site plants was high. Restoration of the meadow's hydrology, while a more expensive treatment, was determined to be the most appropriate, sustainable approach. After nearly 100 years in a straight, deep ditch condition, some lateral cutting (arrows) is contributing to a minor increase in sinuosity while it simultaneously prevents plants from re-establishing. Moving flow to the existing, shallow, sinuous, well-vegetated historic channel would begin major restoration of the stream and meadow in a matter of months.

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Above: Restoration plan for Racetrack Reach included installing several channel plugs, the uppermost of which would be the major diversion plug. Movement of flow into the historic channel significantly increases floodplain connectivity and provides pool habitat for juvenile steelhead. The remainder of the channel plugs trap and detain overland flow in wetland cells, increasing opportunities for infiltration and recharge. Livestock crossings limit cross-channel movement and fencing will exclude cattle from the historic channel and wetland cells.

 


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Above: Before any equipment was brought on site, the crew weed-whacked the spotted knapweed prior to seed maturity. This was done to remove seed heads of this invasive species so that weed seeds would not be transported throughout the site onto bare soils during construction.

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Above: After the tops of the plants were cut, the cut material was bagged and removed from the site.

 


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Above: Ground protection mats were laid on the meadow to reduce compaction and prevent damage to the desirable native plant community.

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Above: Plant salvage was an important component of the construction. Here sedge is being harvested.

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Above: Excavator was also used to harvest several willow clumps.

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Above: Salvaged sedge was placed on tarps, where it was kept covered and moist until construction was complete.

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Above: Keyways were excavated for each ditch plug. Plant materials were salvaged and places on tarps, then covered with burlap, for storage; sedge storage seen left and right of the excavator.

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Above: A mix of clay and structural rock was placed into the keyway, then spread and compacted with a dozer (below).

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Above: Water was available on site during construction to ensure good compaction of the clay and rock that comprises the "backbone" of each ditch plug.

 


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Above: After the clay and rock were compacted into the keyway and built up to raise the elevation of the ditch plug, the tops and sides were covered with several inches of top soil.

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Above: Small "persuasion" connector channels were excavated to help move the flow around the diversion plug (Ditch Plug 1), into the historic channel.

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Above: Latah Soil and Water Conservation District Crew processing and laying salvaged sod onto the face of a newly-constructed ditch plug.

 


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Above: Latah SWCD Crew laying purchased wetland sod mats on face of the diversion ditch plug (Ditch Plug 1).

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Above: Installing purchased wetland sod mats on Ditch Plug 1. The top and upper sides of the plug were seeded and mulched with a weed-free straw mulch.

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Above: Example of past successful revegetation of ditch plugs using sedge sod harvested during construction, laid onto newly-constructed ditch plug in the fall of 2009. Crew is processing and laying sedge (left).

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Above: Same location, the following June (2010). The face of the ditch plug is covered with salvaged sedge sod. The top was seeded and mulched.

 

 


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Above: An unusual high water event in mid-November gave us an early look at the function of the stream/meadow restoration work. Here the flow is back in the historic channel.

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Above: Flow on the floodplain on the east side of the meadow. Main flow is in the historic channel, near the treeline in the background. Arrow shows overland flow detained in wetland cells, which filled and overflowed onto the floodplain.

 


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Above: Photo shows degraded reach of Corral Creek during construction of one of the ditch plugs. Photo was taken from the bottom of the channel, on September 10, 2013.

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Above: Photo taken on November 20, 2013, from the top of bank at approximately the same location. The mid-November high flow event filled the wetland cell behind the ditch plug (arrow) and overflowed onto the floodplain.

 


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Above: Photo of the degraded channel of Corral Creek in Racetrack Reach taken before construction, in early September 2013.

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Above: Photo taken on November 20, 2013 in the Racetrack Reach of Corral Creek, showing capture and detention of flow in wetland cells and floodplain access.

Summary prepared by Trish Heekin, Resource Conservation Planner, Latah Soil and Water Conservation District, 2014

Latah Soil and Water Conservation District
Gritman Medical Park (Federal Building)
220 East 5th Street, Suite 208
Moscow, Idaho 83843
blog.latahsoil.org