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Project Design: Buck
Engineering
Primary Contractor: Byers
Construction
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HYATT
(March 2002)
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Project
Background
This site is along
2,700 feet of Brasstown Creek on the Bass Hyatt farm approximately 3.5
miles west of the community of Warne, NC. Like Bell, this project was
completed in spring 2002.
Prior to
restoration, there was active bank erosion along most of this reach, and
pasture grazing had resulted in little or no riparian buffer along the
upper portion of the reach. The downstream section of the project had
more established buffer than the upstream section and there was also
less bank erosion. Some areas of the stream had become overly wide
because of the excessive bank erosion and this resulted in the formation
of several mid-channel bars. The total estimated soil loss from this
reach of Brasstown Creek was 830 tons per year with an average rate of
erosion of 876 lb/ft/yr.
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Before |
After |
The
goals of this project were to improve water quality and aquatic habitat
by reducing sedimentation, to improve stream stability, riparian and
floodplain functionality, and the natural aesthetics of the stream
corridor. Meeting these objectives along the 2,700 feet of stream
involved removing mid-channel bars and a log debris jam, narrowing the
channel, stabilizing eroding stream banks, and reestablishing an
adequate riparian buffer.
The design included
installing cross vanes to stabilize eroding banks and to center the
thalweg in the channel. A double wing deflector was also used in one
section to center the thalweg and narrow the channel. J-hook vanes and
root wads were installed throughout the reach to stabilize eroding
stream banks. Area disturbed by the removal of the debris was properly
stabilized. A riparian buffer zone was reestablished along both banks.
Fencing and alternative watering for livestock was also provided.
2008 Status
A 1,717-foot reach
of the Hyatt project was monitored in 2005, 2006 and 2007. It is very
stable. Nine structures provide bank protection and grade control
within the monitored reach. With the exception of the uppermost j-hook
vane, which appears to be undersized, all structures associated with
this 6-year old project have very good to excellent function.
Generally, structures did not change between 2005 and 2007. The
restored stream reach is currently classified as a C4 channel. The
streambed slope is 0.002 feet/foot, with a sinuosity of 1.26. Between
2005 and 2007, the median streambed material remained the same, at very
coarse gravel.
The restored reach
contains several riffles and pools, though riffles and runs compose the
majority of the project length. Riffles are typically associated with
the j-hook vanes, while pools are present downstream of the two cross
vanes and in the one meander bend. The 2007 channel pattern is very
similar to that of previous years. Stream bank erosion is not occurring
on a significant scale within the channel.
Vegetation in the buffer is well developed, and there are
many remnant trees. Because restoration disturbance was limited in
scope, planted vegetation is absent from the unrestored side and
localized on the restored side of the stream. Survival of planted
vegetation is good, and there is moderate natural regeneration in the
sampling plots. Herbaceous growth in 2007 was less dense than in
previous years due to drought, but the buffer was still well vegetated.
Maximum air
temperatures were significantly lower in the buffer zone at Hyatt than
in the adjacent field. This project had the highest measured shade
cover (85%) of all the monitored sites. Peak water temperatures were
also consistently lower downstream of the restored reach on the Hyatt
project.
In 2007, the macroinvertebrate assessment downstream of the
Hyatt project yielded a bioclassification of Good, compared to Good in
2006 and Excellent in 2005. As was observed upstream at Bell, EPT taxa
richness and abundance decreased between 2005 and 2007.
3-Year Study
Recommendations
In
addition to continuing to monitor this reach in subsequent years,
recommended actions include:
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Remove
fescue and stiltgrass and re-seed with temporary seed and a native
perennial seed mix, or plant river cane (Arundinaria gigantea),
to increase diversity at the site
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Routinely
monitor the
currently stable areas with high shear stress; specifically at two
locations between stations 8+76 and 9+45, and between stations 13+33
and 14+60
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