In August of this year Ecotone Inc., a
Maryland-based environmental consulting
firm that specializes in stream and
wetland restoration, completed a unique spring
creek restoration project to improve
fisheries habitat. The “Quarry Meadow
Project” of the Falling Spring Branch in
Chambersburg Pennsylvania was designed
to restore more than 3,000 linear feet
of stream, nearly doubling the high
quality trout habitat of the already
nationally significant natural trout
fishery waters.
The Falling Spring Greenway, Inc. (FSG),
a non-profit corporation dedicated to
the restoration and conservation of the
Falling Spring Branch, realized that due
to cattle grazing, damming, and
channelization, the Valley Quarry
section of the stream had, over many
years, degraded to the point that the
shallow waters could not maintain an
adequate flow, depth or temperature to
maintain the trout population. Rod
Cross, president of the local Trout
Unlimited chapter and board member of
the FSG said, “Streams sometimes widen
by themselves, and in doing so become
shallower. The flow is diminished and
silt covers up the good breeding gravel
that trout need. Basically the stream
hasn’t changed its character on its
own.” After previous attempts to improve
the stream through the creation of
deflectors and revetment areas had
failed to achieve the desired results,
it was clear that a much larger effort
was required.
Goals
The FSG set out on the project in
1998 in search of funding with the goal
of restoring 3,000 feet of Falling
Spring from an over-wide pond-like
stream devoid of fisheries habitat to a
faster, narrower and deeper channel with
plenty of deep holes, bank cover, and
woody debris for fish habitat. The
specific objectives of the project were
as follows:
• Narrow the spring channel 50 to 75% in
over-wide reaches;
• Provide a more defined riffle-run-pool
profile to diversify habitat
• Increase low flow velocities
• Increase pool depths
• Increase bank-side and in-stream
overhead cover
• Restore and enhance adjacent riparian
wetland habitat.
Design
In developing the design, a
geomorphic assessment and survey of the
project reach and reference reach was
conducted to determine the appropriate
dimension for the restored channel.
Falling Spring Meadow, a reach of stream
upstream of the project with excellent
fisheries habitat and a healthy wild
rainbow and brown trout population, was
used as the reference reach. Various
geomorphic parameters were measured on
the reference reach such as cross
sections of pools and riffles, channel
profile, pool, riffle , and run slopes,
pool lengths, and discharge.
Dimensionless geomorphic ratios were
calculated based on the reference
measurements such as width/depth ratio,
pool depth/average depth ratio, radius
of curvature/channel width, and riffle
slope to average slope. Discharge was
also measured at both the reference and
project reach.
The hydrology of Falling Spring is
dominated by a series of perennial
springs and the flow of the stream is
not affected by stormwater runoff. As a
result, morphological relations based
upon bankfull discharge were not
applicable, nor was using drainage area
to extrapolate the morphological data
from the reference reach to the project
reach. Discharge measurements were made
at both reaches and the relative
differences in discharge at each reach
were used to develop a conversion factor
to convert the dimensionless ratios from
the reference reach into the range of
acceptable morphological parameters for
the project reach. The discharge at the
reference averaged 10 cfs while the
project reach, one half mile downstream,
averaged 16.5 cfs.
Rather than design with one
engineered channel width and depth, the
minimum, maximum, and average dimensions
of the reference reach were used to
allow for a range of channel dimensions
on the design reach to provide aditonal
diversity and improved aesthetics of the
finished channel shape. The channel
width of the existing channel ranged
from 20 feet to 65 feet, with an average
width of 34.2 feet. The proposed channel
dimensions called for a width of 20 feet
with constrictions as narrow as 5 feet
in several areas to promote velocity
acceleration and to maintain scour
pools. Table 1 summarizes the channel
characteristics and dimensions of the
existing, proposed, and reference
reaches.
Techniques and Structures
Various habitat improvement
structures were proposed in the channel,
including roller eddies, converging rock
clusters, double wing deflectors, and
coarse woody debris (root wad).
Structures were selected and designed
based on their ability to promote
velocity distribution through the
channel that provided enhanced habitat
for trout. Trout prefer holding cover
where velocities are fairly low directly
adjacent to higher velocity lanes where
food is carried through from upstream.
The trout lay in the low velocity areas
but can easily dart into the higher
velocity lane to feed. They also prefer
these areas of “velocity diversity” near
deep water and/or overhead cover.
Converging Roller Eddy: The
structure was designed to create
velocity acceleration into a vegetated
stream bank, creating diverse velocity
distribution in the channel with high
velocities directly adjacent to lower
velocity vectors for optimal feeding and
holding habitat. Between the rows of
boulders, flow is accelerated, creating
additional stream power to scour and
maintain a deeper channel, providing
additional depth. Vegetation is
incorporated in the boulder rows to
create a natural appearance and provide
additional overhead cover.
Converging Rock Clusters: This
structure also creates velocity
acceleration and is similar in design to
a more traditional double wing
deflector. A large boulder, or cluster
of smaller boulders, are placed just
upstream of the deflectors to create
flow convergence between the wing
deflectors. The increased velocities
will maintain a deeper thalweg and scour
channel. Vegetation in the form of
wetland seed, sod matting, and woody
transplants are proposed on top of these
structures to create a natural
appearance and hide the rock.
Double Wing Deflector with Willow
Transplants: Similar in design to the
Converging rock clusters with boulder
placement in the downstream scour hole
to create feeding lanes and resting
areas.
Root Wad: Root wads, normally used
as bank stabilization as part of a
revetment, were proposed for the project
as coarse woody debris. The existing
channel had very little woody debris in
channel because of a lack of upstream
supply and few on-site sources. By
emplacing root wads in the channel,
velocity distribution was enhanced, and
available habitat for benthic organisms
was increased. Vegetation, in the form
of live stakes, will be planted directly
in the root wads to promote vegetative
growth and overhead cover.
Construction
The project, completed in
approximately seven weeks, and had two
phases. Phase one, the construction
phase in which the stream was narrowed
and structures were installed took about
four weeks. Phase two, the dredging
phase, in which a “venturri-system”
suction dredge was used to remove excess
silt from the stream, took about three
weeks. The sequence of construction was
as follows:
Phase I
• Install turbidity control measures to
separate work areas from the main flow;
• Transplant willows and red twig
dogwoods to the new streambank edge;
• Fill the desired area with 4”-12”
clean stone utilizing low ground
pressure dozers
• Excavators and loaders narrowing the
stream from as wide as 65 feet to as
narrow as 5 feet;
• Capture sod from wetland areas away
from the stream and place it along the
banks.
• Backfill over the stone with 3”-12”of
topsoil;
• Seed and mulch the new banks with a
temporary seed mixed with a slower
germinating wetland seed mix.
The stone was placed as a stable
base for the soil. The sod transplants,
placed with a tracked skid steer,
provided instant native vegetation along
the bank to prevent runoff from entering
the stream. Along with narrowing the
banks a large part of the construction
was the installation of the habitat
structures and the enhancement of the
natural meander of the stream. These
features will help the stream to
maintain its improved flow and provide
cover and habitat for trout. The
transplantation of willow and dogwoods
to the new bank will also eventually
further improve the stability of the
banks and provide overhead cover and
food sources for the trout and shade to
help the stream to maintain the cool,
consistent thermal regime.
Phase II
The dredging portion of the project
was designed to remove as much of the
excess silt as possible from the
streambed. Rather than dredging the
entire stream with heavy machinery
during Phase I, a deeper narrower
thalweg channel was dredged and was
sized so that it will be maintained by
the stream over time and will not fill
in. The dredge was also used to clean
out sediments in and around habitat
boulders and the habitat structures. The
4” dredge, powered by a 23 horsepower
motor set on a floating barge, was
custom designed by Ecotone to move over
10 cubic yards of silt per hour. The
silt removed from the streambed was
pumped up on land and was graded into
the surrounding areas and immediately
seeded and mulched to prevent any
further erosion. Through dredging
Ecotone was able to increase the depth
of the stream from as shallow as four to
five inches to as deep as five feet in
select reaches.
As the design-build contractor,
Ecotone coordinated construction and
selected C.D. Davis Excavating, Inc.
from Pylesville, MD, a contracting firm
specializing in wetland and stream
restoration construction, to provide
grading and equipment services.
Funding
To fund this project the Greenway
was able to secure $121,000 from the
Pennsylvania Growing Greener Program and
$75,000 from the National Fish and
Wildlife Foundation while contributing
$15,000 of its own resources for the
project. “This project would not have
been possible without the national, and
state government assistance as well as
cooperation from local volunteer
organization and corporations.” said
Cross. The assessment, survey, design,
404 and state permitting totaled $51,000
while construction costs, includi8ng
planting and construction oversight,
totaled $ 160,000.
Challenges
Challenges and problems encountered
during construction included extremely
soft soils in low area adjacent to the
stream. This, combined with heavy rains
in the beginning of the project, made it
extremely difficult to transport stone
to the fill areas along the stream.
Having low ground pressure dozers and
loaders was a necessity in the soft
areas. Also, the extremely low gradient
of the stream, approximately 0.0006, or
0.06 %, did not allow for major field
changes from the design.
Results
Successes from the project seem to
be evident only days after construction
was completed. Due to the narrowing of
the stream, low flow velocities in the
stream have increased from nearly 0 feet
per second (fps) to over 3 fps in areas
where habitat structures were installed.
Already these increased velocities have
scoured out holes more than four (4)
feet in depth and rainbow and brown
trout have been spotted colonizing these
lunker holes only several days after
they were created.
Electro-fishing efforts performed
by Pennsylvania Fish and Boat Commission
in 1976 indicated biomass of rainbow
trout and brown trout totaling 18.5
pounds/acre and a total of only 40 trout
over 2,500 linear feet. A cursory
electro-fishing effort in September of
2001 found only 2 brown trout in the
reach. Falling Spring is regulated as a
Heritage Angling area and is not stocked
by the Pennsylvania Fish and Boat
Commission in the project area.
Increases in trout numbers in the
restored project reach will result from
re-colonization by the existing rainbow
and brown trout population.
The success of the project in
reaching its original objectives other
than design goals includes the
following:
Landowner support: Nothing is
possible without the landowner’s support
and permission. Valley Quarries, Inc.
was cooperative and helpful throughout
the duration of the project.
Local involvement and support: The
Greenway has worked closely with the
Falling Spring Chapter of Trout
Unlimited. The Greenway and Trout
Unlimited have a long history of
cultivating interest in the watershed
and with its landowners. The
organizations’ credibility and track
record in the community was vital to the
project’s success.
Rigorous design: The design
consultants for the project were
involved in assisting the Greenway
obtain funding for this project since
1996, much of the work in the initial
stages performed on a pro-bono basis.
The same consultants followed the
project through construction. This
brought continuity and consistency
throughout the project and assured that
the design was implemented as intended.
The Future
Ecotone and the Falling Spring
Greenway have also recently announced
the approval of a $200,000 grant from
the Pennsylvania Growing Greener Program
for the restoration of three other
sections of the Falling Spring. Design
of these three projects, which fall
under a watershed permit acquired by the
Greenway are projected to begin in the
spring of 2003.
For more information on this
project, contact Mr. Scott McGill,
Principal and Restoration Specialist,
Ecotone, Inc., at (410) 692-7500; 1204
Baldwin Mill Road, Jarrettsville, MD
21084,
www.ecotoneinc.com |
