Marsh Restoration Underway at Sachuest Point Refuge

By ecoRI News staff

MIDDLETOWN, R.I. — U.S. Fish & Wildlife Service and The Nature Conservancy are working to restore and strengthen salt-marsh habitat at Sachuest Point National Wildlife Refuge to better withstand impacts of sea-level rise and coastal storm surge.

The project focuses on the Maidford River marshlands, adjacent to Third Beach. The work is part of a $1.98 million cooperative agreement between The Nature Conservancy and the Fish & Wildlife Service (FWS), supported by federal funding for Hurricane Sandy recovery. It’s also part of a larger $4.1 million Sandy-funded effort to restore coastal areas from Rhode Island to southern Maine.

Jennifer White, FWS wildlife biologist and coordinator for the restoration project, said work will begin next year to address similar marsh-restoration issues involving the Narrow River at the John H. Chafee National Wildlife Refuge in Narragansett.

White said storm surge and wave erosion, combined with the lack of replenishment from estuaries whose rivers have been dammed or choked off by centuries of development, have left once-hardy tidal-marsh ecosystems at a point where salt-marsh elevations can’t keep up with sea-level rise.

Sachuest Point, the section of the marsh behind Third Beach, is too low to drain properly at low tide, leaving it particularly vulnerable to heavy flooding during storm surges. These prolonged periods of inundation impede the growth of high-marsh vegetation and impact healthy fish and wildlife habitats.

Healthy salt marsh is sometimes able to retreat slowly over time, colonizing adjacent areas as sea level rises. At Sachuest Point, however, the marsh is constrained by Third Beach to the north and upland areas to the east and south.

With little opportunity for migration, the best solution to protect Sachuest Point wetlands is to raise the elevation of the marsh itself, according to White. To do that, FWS and The Nature Conservancy are applying a technique called “thin-layer deposition” — sand is strategically spread onto areas of the marsh that are too low. This technique, combined with high-pressure spray dredging, has been successfully used in coastal areas in Delaware, Maryland and New York to restore marshes adversely affected by accelerated sea-level rise, according to White.

She said elevation enhancement will improve growth of salt-marsh plants and reduce overall deterioration of the marsh, benefiting species such as the federally listed saltmarsh sparrow, which relies on high marsh as nesting habitat. White said marshes also play a key role in cleaning and filtering water, and act as a buffer to absorb wind, waves and flood water — key factor in storm protection.

“The completion of this project will yield a higher marsh than we had before, and we hope to improve tidal flow through the marsh as we have cleared ditches and have added shallow runnels to help drain water,” she said. “Ultimately, the project allows the marsh to last into the future and keep pace with sea-level rise.”

White said the project will raise the elevation of 11 acres of marsh at a cost of $644,000. Through a cooperative agreement, the funds were awarded to The Nature Conservancy, which is working along Rhode Island’s south coast to promote shoreline resiliency efforts, including salt-marsh restoration and oyster-reef construction.

In a bit of good news for coastal ecosystems, however, a new study contends that traditional assessment methods overestimate the vulnerability of salt marshes to sea-level rise, because they don’t fully account for processes that allow the marshes to grow vertically and migrate landward as water levels increase.