Site History

Historically, Allins Cove had several islands of salt marsh and a healthy fringe of typical southern New England high and low marsh plants. It was a wide, well flushed embayment until 1959 when the Army Corps of Engineers (ACOE) placed material (fill) from the dredging of Bullock’s Cove on the southeast portion of Allins Cove filling in about 11 acres of the open water, tidal flats, and salt marsh.  Before restoration, the elevations of the marsh in the filled area placed it above the normal tide range, and it converted to upland and a Phragmites australis marsh. Where the elevations of the fill were not as high, a fringing low marsh of Spartina alterniflora survived.  The presence of the Spartina marsh indicated that a successsful wetland restoration project was possible in the Cove. 

When the fill was disposed of in Allins Cove, it not only changed the salt marsh habitat, but also the configuration of the tidal outlet. Erosion of the western shore of Allins Cove over the five years before restoration was dramatic.  More than three feet of shoreline disappeared in that short time.  Adjacent to Byway Road beach, large chunks of salt marsh peat had eroded away.  The placement of the fill narrowed the inlet due to the westward movement of the sandbar associated with the fill area.  The tidal inlet subsequently narrowed, deepened, and moved toward the western shore.  The restoration plan included re-aligning and widening the tidal inlet, and restortion of the shoreline with material from the fill area. 

Restoration

In the fall of 2005, the ACOE removed over 7,000 cubic feet of fill (see picture) and P. australis from three and a half acres of the disturbed area and regraded the marsh to target high and low marsh elevations.  Historic ditches were reestablished. The outflowing channel of Allins Cove was relocated and a sand spit was created to protect upland and salt marsh on northern side and roadway. In May of 2006, Save The Bay coordinated over a hundred volunteers from the local community to plant the high marsh plants Spartina patens and Distichlis spicata.  High school students from around the state planted Spartina alterniflora they had raised in school greenhouses.  Save The Bay, the RI DEM Mosquito Abatement Coordinator, and the project partners conducted additional creek excavation this spring to improve tidal exchange and decrease mosquito habitat.  Save The Bay and the project partners will create a Management Plan for the site, once restoration is complete.  

Monitoring

Monitoring transects were established to assess the condition of the marsh before and after restoration. A survey of vegetation before restoration showed that Phragmites covered the largest percentage of the marsh followed by much smaller coverages of Spartina alterniflora, the dominant low marsh plant, and Spartina patens, and  Distichlis spicata, the two dominant high marsh plants.  Post restoration monitoring has shown that the area of Phragmites has decreased substantially with the fill removal.  Native low and high marsh species coverage has also decreased due to fill removal, but the increase in restored unvegetated mud flats provides a place for the low and high marsh plants to expand.