Urban marsh island protection

August 2012 » Features » PROJECT CASE STUDY
Restoration that provides flood protection and shoreline erosioncontrol has wildlife's 'seal' of approval
JoAnne Castagna, Ed.D.

As construction workers maneuver bulldozers and spread sand to restore the degrading marsh island – Yellow Bar Hassock in Jamaica Bay, N.Y. – their work is being observed closely by an area resident. The resident is a harbor seal, who has been seen lying on the dredge pipeline and sunning himself as the U.S. Army Corps of Engineers performs its work.

"For the past few months we've seen him on the site. He just keeps doing his thing," said Melissa Alvarez, a senior project biologist with the U.S. Army Corps of Engineers, New York District. "I find it so amazing every time we construct one of these island projects how quickly wildlife will use this area."

This has been the case with the prior marsh islands the Army Corps has restored in Jamaica Bay and is showing to be the case with Yellow Bar Hassock, which was completed this summer. Yellow Bar Hassock is part of a marsh island complex located within the 26-square-mile Jamaica Bay Park and Wildlife Refuge that was the country's first national urban park and one of the Gateway National Recreation Areas.

The refuge is located in an urban area that includes portions of Brooklyn, Queens, and Nassau Counties, N.Y. The area's shorelines are bordered by heavily developed lands including John F. Kennedy International Airport, the Belt Parkway, and several landfills.

The Jamaica Bay marsh islands have been disappearing at a rapid rate during the last century. Since 1924, nearly 80 percent of the islands have disappeared. They are disappearing at a rate of approximately 44 acres per year and more in the last decade. It's believed that a great deal of this degradation is due to regional urbanization.

Restoration of Yellow Bar Hassock marsh island in Jamaica Bay is expected to help protect urban shorelines, such as Manhattan (background), from flooding and erosion. Photo: U.S. Army Corps of Engineers

The Jamaica Bay marsh islands have been disappearing at a rapid rate during the last century. Since 1924, nearly 80 percent of the islands have disappeared. They are disappearing at a rate of approximately 44 acres per year and more in the last decade. It's believed that a great deal of this degradation is due to regional urbanization.

If something is not done to stop this loss, it is estimated that the marsh islands could vanish by 2025, leaving wildlife homeless and threatening the bay's shoreline. According to Alvarez, a certified Professional Wetlands Scientist, maintaining the health of these marsh islands is critical to the well being of wildlife and the 20 million people that live and work in this urban region.

Project
Yellow Bar Hassock restoration, Jamaica Bay, N.Y.

Participants
U.S. Army Corps of Engineers,
    New York District
Port Authority of New York
    and New Jersey
National Park Service (Gateway)
New York City Department of Environmental     Protection
New York State Department of              Environmental Conservation
National Resources Conservation Service
New York/New Jersey Harbor Estuary    Program

Plan
Place and grade dredged sand to restore proper elevations of a marsh island and plant appropriate vegetation to anchor sediments to provide flood protection and erosion control to adjacent urban shoreline areas.

"The marsh islands are home for a variety of wildlife, including fish and shellfish which are an important food source for birds and help improve water quality by removing things like nitrogen and phosphates," Alvarez said. "These islands also serve as flood protection and shoreline erosion control for the bay's surrounding homes and businesses. They dissipate wave energy, minimize storm surge, and provide flood risk reduction benefits."

For the public, this means less erosion to personal property, more species available for recreational fisheries, better water quality, and preservation of the Gateway National Recreation Area that is visited by millions of people each year.

For the last decade, the Army Corps in partnership with other agencies has restored 180 acres of marsh in Jamaica Bay, including Elders East and Elders West marsh islands and Gerritsen Creek. The Army Corps is working with The Port Authority of New York and New Jersey, National Park Service (Gateway), New York City Department of Environmental Protection, New York State Department of Environmental Conservation, National Resources Conservation Service, and the New York/New Jersey Harbor Estuary Program.

To restore Yellow Bar Hassock marsh island, 375,000 cubic yards of dredged sand was pumped on the island and shaped to simulate the proper elevations of a marsh island. This work added an additional 42 acres to the degraded island, restoring it to a 156-acre habitat.

The sand placed on the island was dredged and beneficially used from the Ambrose Channel, part of the Army Corps' New York/New Jersey Harbor Deepening Project. In the past, this sand would have been dumped into the ocean, so this program benefits the environment and taxpayers.

Workers then planted seed on nearly 30 acres of marsh. The team collected the seed from within Jamaica Bay. The low marsh areas were seeded with smooth cordgrass. This plant is a natural anchor for the marsh sediment and can tolerate salt and low tides. In the high elevations of the marsh they planted more than 100,000 two-inch plugs of saltmarsh meadow grass and spikegrass. These plants are less tolerant of salt, but endure the salt water during the moon high tides. These plants also were collected within Jamaica Bay.

Before the sand was placed, the team removed 11,000 hummocks from the marsh island's low-lying areas. Hummocks are mounds of terrain and vegetation above ground that often are made from decaying plants. In this case, they're made up of native smooth cordgrass.

A harbor seal rests on the dredging pipeline, observing restoration work on Yellow Bar Hassock marsh island. Photo: Melissa Alvarez/U.S. Army Corps of Engineers, New York District

The team stored the hummocks in fenced-off areas on the project site and after the sand was placed on the island they transplanted them onto the new areas of higher elevation. Hummocks are a natural anchor for the marsh sediment because they are part of the historic marsh which are already matured and will fill in to stabilize the island.

"The other marsh islands we restored look incredibly vibrant and healthy," said Lisa Baron, project manager, U.S. Army Corps of Engineers, New York District. "One could only hope that's the way the other marsh islands will end up, including Black Wall and Rulers Bar Hassock marsh islands that the Army Corps [planned] to begin working on in August."

A bulldozer levels and pushes out sand to expand the island. The bulldozer is outfitted with GPS to grade the sand to the proper planting height. Photo: Melissa Alvarez/U.S. Army Corps of Engineers, New York District

Yellow Bar Hassock is already beginning to look good. Alvarez said that she spotted Horseshoe crabs laying eggs on the island. Horseshoe crabs haven't been seen in the area; just a year ago this island wasn't suitable for them because it was a barren mudflat. According to Alvarez, "The old adage of 'Build it and they will come' suits Jamaica Bay's islands and specifically Yellow Bar Hassock very well."

JoAnne Castagna, Ed.D., is a public affairs specialist/writer for the U.S. Army Corps of Engineers, New York District. She can be contacted at joanne.castagna@usace.army.mil.


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