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Allen Harbor - Little Mussachuck - Sachuest

Sachuest Salt Marsh Restoration, Middletown

History | Planning | Construction | Monitoring | Lessons Learned

Site Description and History
The Sachuest Salt Marsh is located within the Sachuest National Wildlife Refuge in Middletown, Rhode Island. The marsh is now about 45 acres in extent, although it was originally part of a much larger salt marsh complex in the southeastern part of Aquidneck Island.

View of creek in Sachuest marsh
View of creek in Sachuest marsh
Courtesy: National Marine Fisheries Service

Beginning in the late 19th century and continuing through the mid-20th century, the area was subject to a number of significant alterations that destroyed most of the marsh complex and led to the severe degradation of the wetlands that remained. A large reservoir, Gardiner Pond, was built on the marshes, probably in the early 1900s. During the World War II era and later, Sachuest Point was used as a military installation. A municipal dump was operated on the Point, using the surface of the marsh itself as a dumping area, and later closed. Parking lots were developed for two municipal beaches adjacent to the marsh, Second and Third Beach. In the late 20th century, Sachuest Point, including the salt marsh, was designated a National Wildlife Refuge. Like all such refuges, the area is now managed by the U.S. Fish and Wildlife Service.

Salt marshes require frequent tidal flushing in order to maintain their unique biological characteristics. The Sachuest Salt Marsh is connected to the Sakonnet River, the eastern arm of Narragansett Bay, by way of tidal creek that crosses Third Beach. About 50 years ago, a road was built through the marsh, perpendicular to the tidal creek. A concrete pipe beneath the road was intended to allow the tide to continue to enter the marsh; but the pipe was badly undersized, and the tide was unable to flood the western half of the marsh. Salinity was reduced and, over a period of years, the invasive reed Phragmites came to dominate the restricted part of the marsh.

Restoration Planning
In 1989, the oil tanker World Prodigy ran aground on Brenton Reef, off Newport, Rhode Island - not far from the Sachuest Salt Marsh. The ship spilled nearly 300,000 gallons of home heating oil, killing fish, lobsters and shellfish in Narragansett Bay and Rhode Island Sound. Under federal law, the state and federal governments have the right to sue shipowners and other parties responsible for oil spills, and to use the proceeds to restore natural resources. With funding from the World Prodigy settlement, the National Oceanic and Atmospheric Administration (NOAA) identified the Sachuest Salt Marsh as a restoration opportunity, and funded planning and construction of the project. A number of partner organizations provided essential support and expertise to make the project a reality, including the Town of Middletown, the R.I. Department of Environmental Management, U.S. Fish and Wildlife Service, U.S. Geological Survey (USGS), University of Rhode Island (URI), and U.S. Army Corps of Engineers.

Planning for the project consisted of three major components:

  1. A site investigation by the Corps and others that produced a technical report which recommended an approach to restoration of the site (Corps undated).
  2. An environmental assessment (NOAA 1996), required of federal projects, that evaluated the project overall to establish that it would be practicable and beneficial, and to serve as the basis for environmental permitting.
  3. A baseline ecological study by USGS and URI, which surveyed existing conditions in both restricted and unrestricted areas of the marsh, recording the flora and fauna present (Roman et al. 1997) and serving as the basis for subsequent monitoring efforts.

Construction

Replacing culverts beneath the road through Sachuest marsh
Replacing culverts beneath the road through Sachuest marsh
Courtesy: NMFS

After all the planning work that went into the Sachuest Salt Marsh restoration, construction was almost anticlimactic. Over the course of just a few days in March, 1998, a construction crew from the Middletown Department of Public Works replaced the concrete pipe beneath the road with a set of larger culverts to allow the tide to flood the marsh again. Special wide-tread excavators, designed to work on wetlands, were used to re-open channels that had filled with silt and Phragmites. The Rhode Island Mosquito Abatement Coordination Program designed and constructed an "open marsh water management" project which reduced breeding opportunities for mosquitos by increasing tidal flushing of depressions on the marsh surface and improving habitat for fish that prey on mosquito larvae, like mummichogs and killifish.

Monitoring
The USGS and URI group that undertook the baseline ecological study of the marsh was also responsible for monitoring the restoration. In 1998 and 1999, the group again sampled plants, fish, and shellfish in the part of the marsh that had been tidally restricted as well as the unimpacted area, using a variety of statistical methods to compare the plant and animal communities in both parts of the marsh. The design of the monitoring effort, comparing the restricted and unrestricted areas of the marsh before and after the restoration, provided the opportunity for rigorous scientific assessment of the success of the project.

Researches from URI found that the western side of the marsh had responded well to restoration. Phragmites and cattail, another brackish-water plant, decreased significantly following the restoration, while typical salt marsh species such as salt hay grass (Spartina patens) and smooth cordgrass (Spartina alterniflora) increased. After two years, the vegetation in the formerly restricted area was still quite different from that in the unimpacted area, but seemed to be on a trajectory toward a typical salt marsh plant community.

As would be expected, fauna were found to respond more quickly to the restoration. Just one year after the restoration, fish and crustaceans were as abundant and diverse in the formerly restricted part of the marsh as in the unimpacted area. The most common species was the mummichog, but nearly twenty species were observed, including several other species of marsh minnows, blue crab, black sea bass, American eel, and two species of shrimp (Roman et al. in press).

Lessons Learned

New culverts allowing tidal flow into the restored section of marsh
New culverts allowing tidal flow into the restored section of marsh
Courtesy: NMFS

The experience of the Sachuest Salt Marsh restoration was consistent with results from similar projects throughout the coastal United States, adding to a growing body of data about tidal marsh response to restoration. Marsh flora and fauna both responded strongly to the restoration by becoming more like the biological communities present in unimpacted marshes. Fish and crustaceans responded quickly to the restoration, as their mobility allows them to take immediate advantage of newly created habitats. Plants responded more slowly, but seem to be moving toward the type of vegetative community that would be present in an unrestricted marsh. Several recent studies of restored New England marshes have shown that it may take several decades for salt marsh vegetation to become fully established in the formerly restricted part of the Sachuest Salt Marsh.

References

NOAA, 1996. Final M/V World Prodigy Oil Spill Restoration Plan and Environmental Assessment Narragansett Bay, Rhode Island. (http://www.darp.noaa.gov/neregion/wpea.htm).

Roman, C.T., K.B. Raposa, S.C. Adamowicz, M.J. James-Pirri, and J.G. Catena. In press. Quantifying vegetation and nekton response to tidal restoration of a New England salt marsh. Restoration Ecology.

Roman, C.T., C.L. LaBash, K. Raposa and G. MacPhee. 1997. Restoration of the Sachuest Salt Marsh (Middletown, R.I.): Pre-Restoration Ecological Baseline Information. Unpublished Report. National Marine Fisheries Service, Gloucester, Massachusetts.

U.S. Army Corps of Engineers. Undated. Biological and hydrological evaluation of the Sachuest Point Salt Marsh, Middletown, R.I. Unpublished report. U.S. Army Corps of Engineers, Waltham, Massachusetts.

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