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.
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.
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.
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.
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.
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.
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.
Above: After the tops of the plants were cut, the cut material was bagged and removed from the site.
Above: Ground protection mats were laid on the meadow to reduce compaction and prevent damage to the desirable native plant
Above: Plant salvage was an important component of the construction. Here sedge is being harvested.
Above: Excavator was also used to harvest several willow clumps.
Above: Salvaged sedge was placed on tarps, where it was kept covered and moist until construction was complete.
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.
Above: A mix of clay and structural rock was placed into the keyway, then spread and compacted with a dozer (below).
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.
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.
Above: Small "persuasion" connector channels were excavated to help move the flow around the diversion plug (Ditch
Plug 1), into the historic channel.
Above: Latah Soil and Water Conservation District Crew processing and laying salvaged sod onto the face of a newly-constructed
Above: Latah SWCD Crew laying purchased wetland sod mats on face of the diversion ditch plug (Ditch Plug 1).
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.
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).
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.
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.
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.
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.
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.
Above: Photo of the degraded channel of Corral Creek in Racetrack Reach taken before construction, in early September 2013.
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.