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Section 319
SOURHF PROGRAM SUCCESS STORY
Project Improves Water Quality and Saves Eroding Farmland
WatPrbndv Imnrnvpd 'Dastremova' of woody riparian shrubs made the banks of Bog
'} * '' " ' Brook susceptible to erosion. As erosion continued overtime,
the stream channel became wider and more unstable. This made the erosion problem worse,
sending tons of sediment into the stream. Project partners returned the stream channel to a
more natural state and planted vegetation at the site. As a result, the channel stabilized and
erosion subsided. In 2006, New Hampshire will upgrade the stream from Impaired by other
flow regime alterations to Fully Supporting in its 305(b) surface water quality report.
Problem
Bog Brook is in the Connecticut River Basin,
near the town of Stratford in northern New
Hampshire. Much of the area is in agricultural
use. Decades ago, riparian vegetation was
removed along the streambank, presumably
to increase the amount of arable land. The
absence of deep-rooted shrubs made the bank
vulnerable to erosion. The once meandering
stream channel became marked by a sharper
bend as the bank eroded. This change in
stream channel geometry caused erosion to
accelerate even further. The eroding stream
channel eventually threatened a barn and
septic system on private property, prompting a
need for action.
Analysis of aerial photographs showed that
the stream channel had eroded laterally up
to 35 feet between 1999 and 2003, consum-
ing 4,000-square feet of land. This translated
to 120 tons of sediment—approximately the
amount needed to fill 9 dump trucks—entering
the stream each year to worsen water qual-
ity and smother fish habitat. Had this been
allowed to continue, the stream likely would
have cut a new channel into valuable farmland,
sending several thousand tons of additional
sediment downstream.
In 2004, New Hampshire listed Bog Brook as
Impaired by other flow regime alterations in its
305(b) report with a probable source of stream-
bank modifications/destabilization.
Bog Brook before restoration. Removing riparian
vegetation facilitated channel erosion, which ultimately
threatened the barn.
Project Highlights
The landowner adjacent to the eroding channel
worked with the town of Stratford and a con-
sultant to secure a section 319 grant from the
New Hampshire Department of Environmental
Services (NH DBS). The project called for a
comprehensive stream morphology assessment,
design plan, and reconstruction of a 275-foot
stretch of the stream to a more natural condition.
The partners developed the project using
natural stream channel design methods. In
the past, landowners and engineers typically
turned to hard bank armoring for streambank
erosion problems. Because armoring treats
only a symptom rather than the cause of bank
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Results
Bog Brook after restoration. The project saved the barn
and stopped several thousand tons of sediment from
smothering fish habitat.
erosion, it is often ineffective over the long
term. Natural stream channel design uses
a stable reference stream to determine the
proper slope, width, depth, and geometry
needed to restore the impaired stream. To
restore channel stability in Bog Brook, project
leaders determined it necessary to
• Increase the meander radius, or curva-
ture of the bend in the stream, to reduce
stress on the eroding bank
• Increase the channel slope to improve the
stream's ability to transport sediment
• Plant a vegetated buffer of deep-rooted
shrubs along the streambank to help hold
sediments in place
Construction occurred in May 2004. Using an
excavator, a small bulldozer, and several dump
trucks, project leaders realigned the stream
channel, filled in the former channel, and plant-
ed riparian vegetation along the streambank.
Post-construction monitoring the following
year confirmed that the work had stabilized
the stream system. The table below compares
the reference stream with Bog Brook, before
and after construction, using the three major
factors determining Bog Brook channel stabil-
ity. The table shows that Bog Brook, after
construction, more closely matched the stable
reference stream conditions.
One year after construction, the relocated
stream reach had become more narrow and
deeper—a positive trend indicative of channel
stability. The vegetation along the bank was
found to be well-established and firmly rooted.
On the basis of these post-construction find-
ings, the state concluded that severe bank
erosion had been arrested, and the sediment
load to the stream had been significantly
reduced. These conclusions allowed the state
to upgrade Bog Brook to Fully Supporting in its
2006305(b) report.
Partners and Funding
The Bog Brook restoration effort involved
several partners who provided financial and
in-kind contributions. The NH DBS Watershed
Assistance Section awarded the town of
Stratford a $14,912 section 319 grant to par-
tially fund survey, design, permitting, and
construction. The property owner contributed
$8,748 in additional funds. In-kind professional
services for construction supervision com-
prised the remainder of the required nonfed-
eral match. The total project cost $24,460.
Factor in Bog Brook channel
stability
meander radius
channel slope
vegetation
Reference stream
80-120 ft.
—
deep-rooted
riparian shrubs
Bog Brook
Pre-construction
40ft.
.081%
shallow-rooted (6-in.) grasses
(e.g., timothy, reed-canary
grass, Kentucky bluegrass,
orchard grass)
Post-construction
92ft.
1.00%
deep-rooted riparian
shrubs (e.g., alder,
willow)
'. U.S. Environmental Protection Agency
\ Off ice of Water
a Washington, DC
EPA841-F-06-003E
June 2006
For additional information contact:
Eric Williams
New Hampshire Department of Environmental Services
603-271-2358
ewilliams@des. state, nh. us
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