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Project Design:
Mulkey Engineers & Consultants
Primary Contractor: Ownbey Bulldozing
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MASON/STALCUP
(January - February 2005)
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Project
Background
The Mason/Stalcup project site is located along an upper reach of Little
Brasstown Creek and Pinhook Branch on the properties of John Mason,
Keith Stalcup, and Mary Edith Stalcup. This project is situated
immediately upstream of the Sheppard project. Land use is primarily agriculture with livestock grazing
on one side of the stream and a hayfield on the other. The Mason/Stalcup
project is HRWC’s most recent stream restoration project in the
Brasstown Creek watershed; construction was completed in winter 2005
shortly before this monitoring effort began.
Prior to project construction, both Pinhook Branch and Little Brasstown
Creek were moderately unstable. The streams had been channelized and
dredged historically. Active scouring was evident throughout most of
the reach, though the areas were limited to the outsides of meander
bends, both upstream and downstream of debris, and near niche points
consisting of either large boulders or bedrock. Riparian vegetation was
limited to one row of mature trees with frequent breaks on the right
bank and a few scattered mature trees, along with lots of exotic
vegetation on the left bank. The objectives of restoration efforts at
Mason/Stalcup were to reduce stream bank erosion and improve aquatic and
riparian habitat.
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Before
Little
Brasstown Creek was too sinuous and actively eroding in this
location below the confluence of Pinhook Br.
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After
The bend
was restored to a more stable pattern and the banks were
sloped, matted and seeded. Also, trees were planted on
both banks within the 50-ft buffer area. |
Floodplain benches were constructed along several sections of bank, the
largest being 25 feet in length, to reduce stresses in the channel at
high flow. Cross vanes were constructed along the 1,900 linear-foot
reach to help reduce the width/depth ratio and provide bank stability,
grade control and habitat for aquatic life. Rock vanes and j-hook vanes
were constructed along the outsides of meander bends requiring
stabilization to help redirect flows away from the outside banks,
provide limited bank stabilization, and enhance habitat for aquatic
life. The j-hook vanes were installed in bends containing existing or
degraded pools to help maintain localized scour required for continuous
pool maintenance. Existing spoil piles from historical dredging
activities were removed or relocated and reduced in height to create
more floodplain area and to enhance riparian habitat. Vertical banks
were sloped and stabilized using root wads or matting and live stakes at
selected locations.
Native trees and shrubs were used to restore the 50-ft riparian buffer
area along both sides of 1,500 feet of Little Brasstown Creek (including
500 feet upstream of the confluence of Pinhook Branch where no
restoration activities were conducted), and approximately 900 feet of
Pinhook Branch.
2008 Status
The entire restored
reach at Mason/Stalcup was monitored in 2005, 2006 and 2007. It is very
stable, with very little notable bank erosion. The restored project,
which is composed of both Pinhook Branch and Little Brasstown Creek
contains 19 in-stream structures. The structures are single arm rock
vanes, rock cross vanes, and rock j-hook vanes. With the exception of
one structure that has been compromised due to adjacent road
stabilization, all structures are in very good or excellent condition.
The restored reach is currently classified as an E4 channel. The
streambed slope is 0.008 feet/foot, with a relatively low sinuosity of
1.12. Since 2005, the streambed material has become coarser. The
median particle size is currently coarse gravel.
The restored reach
has several stable riffles and deep pools. Nearly all of the pools are
associated with a structure. Riffles and runs dominate the Pinhook
Branch portion of the project, while pools are predominant in the Little
Brasstown Creek portion. The few riffles in the lower part of the
restored reach are typically found at the heads of j-hook and single arm
vanes. The locations of riffles and pools generally did not change
between 2005 and 2007. Cross-section dimensions also remained very
similar between 2005 and 2007. Despite some meander bends, shear stress
throughout the reach is typically low to moderate, largely due to the
success of the structures. Bank erosion is essentially non-existent due
to the lowered shear stress, the well-vegetated right bank, and access
to the floodplain.
The Mason/Stalcup
project had the lowest percentage of shade cover (59%) of the 10
monitored sites; however, this level is still considered moderate and is
likely due to the young age of trees and shrubs throughout most of the
buffer. Newly planted vegetation at Mason/Stalcup is generally healthy,
though the 2007 drought interacted with poor soil in some areas to
depress recovery. Throughout 2007, vegetation on the left bank was
mowed to the edge of the water. As a result, very small areas of bank
erosion are beginning to develop. If mowing continues, bank erosion
will increase and the stability of some structures may eventually be
compromised.
Storm event samples collected downstream of
the restored site were lower in Total Suspended Solids (TSS) than
samples collected upstream by an average of 36%, with only one of the
eight samples exhibiting an increase. Levels of TSS on the upper end of
the project indicate a need to reduce erosion from upstream sources.
The
macroinvertebrate assessment yielded a bioclassification of Good/Fair
for 2007, which represents a change from the Good bioclassifications in
previous years. Between 2005 and 2007, EPT taxa richness and abundance
decreased slightly.
3-Year Study
Recommendations
Recommended actions
at Mason/Stalcup include:
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Consider early
removal of
invasives to
prevent later large-scale problems
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Work
with landowners
to discontinue (or minimize) mowing on left bank
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Evaluate
the watershed
upstream for the potential to reduce sources of TSS
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