Harbor - Little Mussachuck
Little Mussachuck Creek Marsh Restoration,
Site History | Planning |
Construction | Monitoring |
Benefits | Lessons Learned
In a true show of community-based restoration, Save The Bay and
the Barrington Conservation Land Trust set out to restore a tidally
restricted marsh in Narragansett Bay. With all permits and technical
expertsí recommendations in hand, in April of 1998, Save The Bay
directed a corps of over 70 volunteers to restore tidal flow to
Little Mussachuck Creek, a salt and brackish wetland located in
upper Narragansett Bay.
The Barrington Conservation Land
Trust, the owner and steward of the marsh, had been monitoring the
expansion of common
reed (Phragmites australis) since the mid 1990s and had
seen a significant increase in its spread at the expense of other
plant species, many of which were species of statewide concern.
The Land Trust believed that rare native brackish marsh plants were
in danger of extirpation at the site due to the continued expansion
of the invasive Phragmites in the northern portion of the
marsh. The Land Trust sought the expertise of Save The Bay to coordinate
the restoration of Little Mussachuck Creek in 1997. The objectives
of the restoration project were to evaluate a range of restoration
alternatives and carry out a restoration action that would conserve
rare wetland plants: creeping spikerush (Eleocharis rostellata),
maritime sea blite (Suaeda maritima), salt marsh bulrush
(Scirpus maritimus), and leafy bulrush (Scirpus robustus).
|Aerial photo of Little Mussachuck Creek marsh
Courtesy: Save The Bay
Like most back barrier marshes, Little Mussachuck Creek marsh formed
in response to changes in sea level and localized effects of barrier
beach migration, storm overwash events, shifts in tidal inlet positions,
and changes in biogeochemical processes. The marsh consists of approximately
25 acres of estuarine salt and brackish wetlands and approximately
10 acres of open water and mudflat habitats. The western edge of
the marsh is bounded by a narrow barrier beach, Annawamscutt Beach,
which separates the wetland from Narragansett Bay. Little Mussachuck
Creek empties into Narragansett Bay at its southern end where it
forms an ebb/flood-tide delta. A tidal inlet historically connected
the northern portion of the marsh to Narragansett Bay. The closure
of this tidal inlet has been the focus of this restoration.
The build up of beach sands in the northern part of the barrier
beach had begun restricting the northern inlet to Little Mussachuck
Creek by 1990. By 1998, this tidal inlet was completely cut off
from daily tidal influence. At Little Mussachuck Creek, the mean
long shore deposition is in a northerly direction. This is evident
by observed deposition patterns in the beach. Longshore deposition
processes are a coastal geologic phenomena that influence the structure
of barrier beaches, resulting in the distribution and movement of
sediment along the shoreline. Longshore processes are caused by
the interaction of tidal currents, prevailing wind patterns, and
beach geomorphology. Longshore currents are believed to be impacted
by the severity of shoreline hardening by sea walls and bulkheads
owned by property owners adjacent to Little Mussachuck Creek. One
particular sea wall extends perpendicular to the barrier beach and
acts as a trap for sediment carried in longshore currents.
The Bay and members of the RI Habitat Restoration Team visited Little
Mussachuck Creek in 1997 to evaluate restoration options. The group
agreed that disruption of longshore sedimentation had altered the
barrier beach of Little Mussachuck Creek. Closure of the northern
inlet was believed to be the likely impetus for Phragmites
invasion and consequent changes in the marsh plant community. The
inlet closure had resulted in the impoundment of fresh water in
the northern portion of the marsh, flooding salt marsh species,
and allowing Phragmites to gain a foothold. The closure of
the northern tidal inlet changed the upper marsh from a characteristic
high salinity emergent wetland to a fresh and brackish pond with
infrequent tidal inputs. Concurrent changes in water chemistry and
a reduction in tidal signal have been followed by the colonization
of the marsh by monotypic stands of Phragmites. Additionally,
continued inundation by fresh water had deteriorated the high salt
marsh peat adjacent to the flooded pond. This had the potential
to lead to marsh subsidence.
Save The Bay and the Land Trust were fortunate to work with the
R.I. Habitat Restoration Team, composed of technical experts from
U.S. Fish and Wildlife Service (USFWS), the Rhode Island Department
of Environmental Management (DEM) and the University of Rhode Island
(URI). The team assisted in the evaluation of the restoration options
for restoring Little Mussachuck Creek marsh. The decision to restore
tidal hydrology to northern portions of Little Mussachuck Creek
was based on careful deliberation and recommendations by state and
regional salt marsh restoration technical expertise. The Barrington
Land Conservation Trustís preferred restoration alternative was
determined by acquiring technical resources from the following groups.
- Tom Steinke. Fairfield, Connecticut Conservation Department.
Summer 1995 site visit.
Recommendation: Create a connector ditch from the existing
creek to the northern pond.
- Rhode Island Habitat Restoration Advisory Committee, Salt
Marsh Work Group. The group included leading wetland scientists
from URI including Dr. Frank Golet as well as Brown University,
U.S. Environmental Protection Agency (EPA), USFWS, DEM, and RI
Coastal Resources Management Council (CRMC). They visited the
site during the summer of 1997.
Recommendation: Excavate a new channel from Little Mussachuck
creek to the salt panne and create a sill ditch from the salt
panne to the northern pond.
- Barrington Conservation Commission Salt Marsh Working Group.
In winter 1997, Little Mussachuck Creek was identified as one
of the highest ranked marshes for restoration, as evaluated through
quantitative prioritization and assessment of potential restoration
projects in Barrington.
Recommendation: Evaluate restoration alternatives and decisively
implement restoration actions to conserve rare and sensitive plant
Three alternatives were developed for U.S. Army Corps of Engineers
Section 404 permit requirements:
the barrier beach
- restoring tidal connection between the creek and pond
The preferred alternative selected by the restoration team was
to restore tidal hydrology to the northern marsh and pond complex
by excavating connector channels to the existing tidal channel draining
to the southern inlet. The new channel was engineered to maintain
surface water in upper brackish pond, allow fresh surface water
to drain out of the pond, and to convey tidal inputs into the pond
during spring high tides. This approach represented the best long
term sustainable option for restoring tidal hydrology to the northern
pond of the marsh, stemming the invasion of Phragmites by
increasing salinity levels, and protecting threatened populations
of creeping spikerush (Eleocharis rostellata), salt marsh
bulrush (Scirpus maritimus), leafy bulrush (S. robustus),
and maritime sea blight (Suaeda maritima).
|Volunteers digging a 300-foot channel in Little
Mussachuck Creek marsh
The shovels hit the peat in April 1998
Permits were received from DEM, CRMC and the U.S. Army Corps of
Engineers. The Barrington Conservation Land Trust received a Partners
in Wildlife grant from USFWS to create a restoration tool bank of
shovels, scythes, boots and other equipment for this and future
community-based restoration projects. Armed with shovels, milk crates,
and buckets, close to 100 volunteers, ranging from local high school
students to retired engineers dug a 300-foot creek connecting the
restricted section of the marsh to the unrestricted section of marsh
leading to Narragansett Bay. Even the Governor of Rhode Island,
Lincoln Almond, donned boots to visit the work site.
While the volunteers dug the creek, Save The Bay staff used a laser
level to check the depth and width of the creek to ensure the proper
creek geometry. The volunteers who participated in this project
were forewarned that this would be hard, wet, and dirty work, and
not a soul complained as they dug and hauled hundreds of pounds
of saturated peat and Phragmites rhizomes for the entire
project. Phragmites was composted in a covered and secured
location on a farm field adjacent to the marsh.
Four transects were set up in the upper northern portion of the
marsh to best characterize expected changes in plant community structure
following restoration actions. The four transects were randomly
located across this area of the marsh using a random numbers table.
Transects were all positioned along a perpendicular gradient from
upland soil to tidal creek or open water (Figure
Vegetation. Save The Bay's Andy Lipsky and Wenley Ferguson
collected Mussachuck creek vegetation data in September 1998.
Total plant species (grasses, forbs, shrubs, trees) were identified
and relative cover determined using a line intercept method. Every
0.25-meter section per 1-meter or 2-meter interval was sampled.
Relative cover along the 0.25-meter linear was allowed to exceed
100 percent due to overlapping species cover. Click
to open the data in an Excel spreadsheet.
Biogeochemistry and Hydrology. Distance of plot to open
water was determined with meter tape. Shallow wells (55 cm depth),
constructed from 3-inch diameter PVC with 1/8-inch pores and open
on the bottom, were constructed and deployed during spring 1998
to measure porewater salinity within the active plant root system.
Three wells were installed along each transect, placed randomly
within three distinct zones: upland, high marsh, and low marsh
Porewater salinity was recorded with a hand refractometer during
spring and neap tides with an effort to sample at the time of
low tide. Sampling occurred randomly throughout the1998 growing
season. Data was collected by Save the Bay (STB) staff, interns,
and trained volunteers. Water levels were noted only when water
elevations dropped below the measurable length of well or when
tide-water levels rose above the well top. Wells were not installed
in Transect 4. A surface water collection station located in the
upper pond in the vicinity of Transect 4 served as a proxy for
porewater salinity for Transect 4. Because this upper marsh never
exceeded oligohaline (0.5 to 10 practical salinity units) levels,
porewater salinity in subsurface soils of Transect 4 was believed
to follow surface water variation. Click
to open the data in an Excel spreadsheet.
Phragmites Height and Distribution. Permanent quadrats
were located within Transects 2 and 3 in an established Phragmites
community. In each quadrat (0.5-meter square rectangular), live
and dead Phragmites shoots were counted and measured for
12 randomly selected shoots. Permanent photo stations were set
up at Transects 2 and 3 to monitor Phragmites height over
time. To measure lateral growth of Phragmites along the
leading edge of the stand, oak markers were set in 1998 at approximately
10-meter intervals. Each year, the distance of the leading edge
of the most forward above ground Phragmites shoot is measured
from the 1998 oak stake (Figure
3). Photo-stations are established at key locations to document
the height and spread of Phragmites.
Benefits of the Restoration
Today the meandering creek carries the fresh water out to Narragansett
Bay and carries the Bayís salty waters into the marsh during spring
high tides. Phragmites remains a dominant member of the plant
community at Little Mussachuck Creek and future actions will be
based upon upcoming monitoring. Erosion at the southern end of the
marsh has increased in the past four years and will be addressed
in future management decisions.
|Little Mussachuck Creek marsh, June 2001
The marsh, once flooded with fresh water, now reveals mud flats
which creeping spikerush and salt marsh bulrush began to colonize
during the first growing season. These same mud flats have provided
feeding habitat for shorebirds including greater and lesser yellowlegs,
semipalmated plovers, glossy
egrets, and snowy
herring, and American
eels have all been observed using the new channel to access
upstream marsh and open water habitats.
Lessons Learned - Community Involvement and Monitoring
Many, if not most, marsh restoration projects are too large a scale
for an on-the-ground volunteer project. Yet this project proved
that volunteer involvement can occur at every stage of restoration,
from conducting restoration monitoring and attending planning meetings,
to channel digging, hauling out buckets of muck, transplanting salt
marsh sod, and conducting post-restoration monitoring.
Community members and volunteer monitors played an integral role
in the restoration project.
At the early stages of the project, community involvement was solicited
to ensure that local residents were both educated and aware of the
benefits, potential costs, and the value of restoration. Local citizens
provided valuable information about the history of the marsh. Local
knowledge was key to identifying what, how, and when disturbances
occurred to the marsh and what plants and animals used to be found
in the marsh. Volunteer monitors have gathered important data that
is now being used to determine adaptive management actions at Little
Mussachuck Creek. As proven by the Little Mussachuck Creek restoration,
a group of dedicated and hard-working volunteers with the proper
guidance and expertise can make a marsh restoration project a reality.
It is has been important to establish a realistic monitoring plan
and schedule that can be easily conducted with available expertise
and resources. Permanent photo stations have been a simple yet effective
way to monitor long-term changes in the marsh, specifically the
coverage, height, and density of Phragmites. STB staff, interns,
and experienced community volunteers conducted intensive vegetation
sampling. This intensive sampling was conducted in 1998 and 1999
with the next scheduled monitoring to occur in 2002. Unfortunately,
at the time of the restoration, monitoring guidelines had not been
developed for Rhode Island salt marsh restoration projects. Since
the development of the monitoring methods, efforts have been underway
to develop consistent monitoring guidelines for restoration projects
throughout the state.
The restoration approach taken thus far has been to act, monitor,
and evaluate. The underlying issue of sedimentation, erosion, and
human alteration of the shoreline continues to remain an outstanding
issue at the site. In 2002, Save The Bay and the Barrington Conservation
Land Trust will evaluate the performance of our actions so far.
In order to do this we will review vegetative and hydrologic data,
reconvene a technical advisory team, and pursue any recommended
adaptive management actions. Future phases of the restoration effort
may incorporate the need to maintain or enhance the existing tidal
inlet, control Phragmites abundance with other control methods,
and obtain coastal geologic expertise to develop a long-term management
plan for the site and adjacent shoreline properties.
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