History of the Salt Marsh

 In 1915, Gerard T. Hanley Sr. built a dirt road across the marsh in order to access his seaplane docked on the banks of the WarrenRiver.  Today the road, now a footpath bordered by woody vegetation, continues to allow users access to the WarrenRiver and other portions of the marsh, but has caused degradation of the adjacent marsh. The footpath restricts tidal flow into the southern portion of the marsh even at spring tides. The severity of this restriction is due to the footpath itself and the recent collapse of several stone culverts. Both open and clogged mosquito ditches run through the marsh as well. Members of the Land Trust have observed and noted the increase of the Phragmites australis along the bike path since its completion in 1992. 

 

Restoration Planning and Assessment

In 1996, volunteers identified Jacob’s Point salt marsh as a potential site for restoration through Save The Bay’s evaluation of the ecological integrity of Narragansett Bay’s salt marshes. In 1997, the RIDEM Mosquito Abatement staff created a GIS map of the salt marsh vegetation zones. Since that map was created, the amount of Phragmites australis has increased dramatically. Save The Bay also mapped the edge of the Phragmites australis during a 2 year period from 1997 to 1999. The average rate movement of Phragmites australis from the upland into the marsh was 1.3 meters.  In July of 1999, Save The Bay conducted a tidal survey to determine the severity of these restrictions. Tidal flow lagged more than five hours behind the WarrenRiver, and the level of high tide was over four feet lower than the WarrenRiver, meaning that the water from an incoming tide did not begin to enter the marsh until an hour before high tide.

The Warren Land Conservation Trust has entered into a partnership with the Natural Resources Conservation Service through their Wetlands Reserve Program to restore the tidal hydrology of the marsh.   NRCS’s hydraulic engineer will conduct a hydrologic model to determine the size of the openings in the dirt footpath, the size and extent of new tidal creeks and the amount of fill removal. To develop the hydrologic model, NRCS set out tide data loggers during a month’s tidal cycle in 2006.  In addition, elevation data has been collected through aerial photography and photogrammetry by the Rhode Island based consultant Aerotech, Inc. Photography and photogrammetry are funded by the partnership between NOAA’s Community-based Restoration program and Restore America’s Estuaries. In order to more accurately establish elevations within the large area of Phragmites, Al Gettman of RI DEM’s Mosquito Abatement Program, cut transects through the thickest stands, using a low pressure machine. NRCS staff established control points used by the consultant. NRCS staff will also map the coverage of Phragmites australis. 

Based upon the results of the NRCS model, the restoration plan includes replacement of the collapsed stone crossings with wide culverts to allow for flow of tidal waters across the marsh. The plan also includes maintaining existing creeks and creating new creeks in the marsh and along the marsh perimeter to improve tidal flushing to the restricted side of the marsh and to facilitate mosquito abatement.  The restoration project will include a plan to reduce the mosquito population. DEM’s mosquito control coordinator created a plan to dig new creeks to improve tidal flushing of stagnant pools of water in the upper marsh and to dig ditches along the perimeter of the marsh to reduce freshwater flow from the upland to reduce mosquito breeding habitat. 

Save The Bay in conjunction with the Warren Land Conservation Trust and NRCS has presented the restoration project to the Audubon Society of Rhode Island who owns property along the southern section of the marsh. The project partners will work in collaboration with the Audubon Society of Rhode Island in the development of the restoration plan. The majority of the Audubon wetland property is fresh and brackish marsh dominated by Phragmites australis and a stand of cattails.   Restoring the tidal flow into this section of the salt marsh may result in reduced height and vigor of the stand of Phragmites on the Audubon property.


Monitoring

Save The Bay finished its second year of pre-restoration monitoring in 2006 including soil salinity, vegetation, and fish monitoring, funded by the partnership between NOAA’s Community-based Restoration program and Restore America’s Estuaries. Monitoring results showed that Phragmites does cover a significant portion of the marsh (nearly 60%). The tidal restrictions have indeed impounded freshwater in the restricted portion of the marsh, and water logged the soils. The salinity of the marsh soil averaged 15 parts per thousand, and the depth of the water table averaged only 2 centimeters below the surface of the marsh. The collapsed culverts and the extent of Phragmites have also limited use of the marsh by fish and crabs in the fall.  Save The Bay is collaborating with the Audubon Society of Rhode Island on monitoring the bird use of the salt marsh. Save The Bay expanded our monitoring transects into the unrestricted portion of the marsh to act as a healthy reference for all of our upper Bay restoration sites.