Westchester County

23) Harbor Island Park

23) Harbor Island Park Salt Marsh, Mamaroneck

Harbor Island ParkHarbor Island Park lies next to Mamaroneck Harbor, part of Long Island Sound, and is used for active and passive recreation. A peninsula flanked by the harbor’s East and West basins forms the middle of the park, where much of the active recreation takes place. Most of the park sits atop soil, rock and other materials used to fill in environmentally valuable tidal wetlands in the early 20th Century.

Along the West Basin, tidal wetlands still cling to the water’s edge next to a concrete and stone retaining wall encircling much of the basin. The basin is used as a boat mooring. Along the west side of the basin next to a lawn used for active and passive recreation, fill had created a steep embankment along the water’s edge. The embankment and part of the areas above it were largely covered with invasive plants, including Japanese knotweed, common reed and garlic mustard. A thin band of smooth cordgrass (Spartina alterniflora), an  intertidal wetland plant, clung to the toe of the embankment.

The project, begun in earnest in March 2007 and completed in June 2007, involved cutting back the embankment created by the fill to increase the intertidal zone's width and create a gentler slope. The fill excavated from the embankment was used to create a raised landscaped bed or "berm". The disturbed areas created by the excavation and filling were temporarily stabilized using mesh "blankets" made from coconut fibers. Log-shaped rolls of coconut fiber were also staked into the ground at the water's edge to curb the erosive force of incoming waves. Eventually, all of the coconut fiber products will decompose but, by then, the newly installed plants will be providing long-term stabilization. The created intertidal area (low marsh), embankment, and top of the embankment were planted with appropriate native vegetation, e.g., smooth cordgrass has been planted in the intertidal area, salt marsh hay and marsh elder has been planted in the high marsh, and a variety of coastal grasses, shrubs and trees have been planted on the embankment, along the top of the embankment, and berm.photo23secondary

In addition to these features, a public walkway has been constructed along the top of the berm and embankment and an observation platform has been constructed from the walkway. This allows the public to get a closer look at the salt marsh and other coastal plantings and harbor. Three educational signs were installed along the walkway describing the coastal ecosystem.

During the construction phase of the project, all excavation took place in upland, or non-wetland, areas. The total area of restored salt marsh was  approximately 0.3 acres (13,000 square feet). In addition, the restored upland area was approximately 0.4 acres (17,000 square feet). The site is now being monitored to ensure the project’s success.

After restoration, smooth cordgrass  growing at the water's edge became lush and salt-tolerant plants on the embankment took root.

To View The Site: The site is at Harbor Island Park near Rushmore Avenue in the Village of Mamaroneck. Specifically, it is along the west side of the West Basin, from the end of the existing retaining wall to the edge of village-owned parkland terminating at a privately owned marina.