Beneficial Uses of Dredged Sediment

US Army Corps of Engineers

Jamaica Bay Marsh Islands

It is estimated that approximately 1,400 acres of tidal salt marsh have been lost from the marsh islands in Jamaica Bay, New York since 1924, with the system wide rate of loss rapidly increasing in recent years. Source: USACE New York District.
  • Title: Jamaica Bay Marsh Islands
  • State: New York
  • Project type: USACE
  • Greater Beneficial Use Area: Jamaica Bay
  • Focus Area approximate center coordinates: 40.6177, -73.8248
  • Nearest Federal Navigation Project: Jamaica Bay Navigation Channel
  • Owner: USACE New York District
  • Beneficial Use Categories: Wetland Habitats
  • Dredge type: Hydraulic
  • Status: Completed
  • Keywords: island restoration, saltmarsh, Spartina alterniflora, erosion control, habitat creation

Description:

Jamaica Bay, situated between Brooklyn and Queens, in southeastern New York City, spans approximately 26 square miles and connects to the Atlantic Ocean via the Rockaway Inlet. Recognized for its ecological significance by the US Fish and Wildlife Service, the bay is a vital ecosystem, home to a diverse range of fish, birds, and other wildlife. Central to this ecosystem are the Jamaica Bay Marsh Islands, comprising around 15 islands of varying sizes that are integral to the bay’s urban ecosystem health and a focal point for restoration efforts. These islands are named "marsh islands" due to their predominant composition of tidal salt marshes, which feature vegetation uniquely adapted to the saline conditions of the coastal environment.

Over the past century, Jamaica Bay's delicate ecosystem has faced degradation due to human encroachment, subsidence, sea level rise, erosion, pollution, and plant mortality. Since 1924, the bay’s Marsh Islands have experienced substantial tidal salt marsh loss, with a recorded rate of over 40-acres per year between 1994 and 1999. If this trend had continued unaddressed, the islands could have eroded or become complete inundated by 2025, jeopardizing wildlife habitats and threatening the stability of Jamaica Bay’s urban shorelines.

In response to the chronic loss of marshland, the US Army Corps of Engineers - New York District (NAN) partnered with the New York City Department of Environmental Protection, New York State Department of Environmental Conservation, and Port Authority of New York and New Jersey. The collaborative team sought to elevate the island surfaces to a suitable level for smooth cordgrass (Spartina alterniflora) growth by strategically placing sediment dredged from nearby navigation channel. Additionally, native saltmarsh vegetation was transferred and planted to enhance marsh creation. NAN identified five islands for restoration: Elders Point East (40 acres), Elders Point West (40 acres), Yellow Bar Hassock (45 acres), Black Wall (20 acres), and Rulers Bar (10 acres).

The restoration effort at Elders Point East restored 40 acres of marsh in 2006-2007, followed by an additional 40 acres at Elders Point West in 2009-2010. The restoration efforts involved the placing hydraulically dredged sediment from the New York & New Jersey Harbor Deepening Project, transplanting existing saltwater cordgrass, and constructing hummocks – elevated mounds typical in marsh or wetland environments, composed of organic material, sediments, or plant debris. This collaboration not only addressed sediment disposal challenges but also offered a cost-effective and sustainable solution, merging navigation projects with ecological restoration.

In 2012, a significant restoration project was undertaken at Yellow Bar Hassock, utilizing sediment dredged from the Harbor Deepening Project to create a new marsh island of 67 acres and approximately 45 acres of wetlands. This included placing 375,000 cubic yards of sand, planting over 20,966 high marsh transition plants, and relocating 13 acres of hummocks.

The restoration of Black Wall and Rulers Bar marsh islands in 2012 further extended the scope of the Jamaica Bay restoration project. Sand dredged from the Ambrose federal navigation channel harbor deepening project was beneficially used to create an additional 30 acres of marsh island habitat for these islands.

The project team’s continuous monitoring gathers crucial data that aids in adaptive management and informs future restoration initiatives. Preliminary outcomes suggest that the restoration of the Jamaica Bay Marsh Islands has been successful. For example, by 2017, Elders Point East showed significant ecological progress. The area's plant life and marsh ecosystem were developing in a way that mirrored the reference conditions of a naturally thriving salt marsh. This was evident in the increased density, growth, and vigor of marsh plants and their ecosystem interactions, all of which were aligned with the conditions of a vibrant, undisturbed salt marsh. The utilization of dredged sediment has proven effective in restoring a significant habitat area, thereby substantially restoring the ecological functions within the Jamaica Bay ecosystem.

The Jamaica Bay Marsh Islands Restoration Project stands as a testament to the collaborative efforts of federal, state, and local agencies in preserving and restoring the ecological balance of Jamaica Bay. Combining innovative restoration techniques, community involvement, and continuous monitoring, this project not only addresses immediate environmental challenges but also lays the groundwork for sustained environmental health and resilience in this critical urban estuary.

Further readings:

Website links:

Videos:

Marsh Islands of Jamaica Bay. YouTube, Uploaded by Jamaica Bay-Rockaway Parks Conservancy, 3 July 2021.


News releases:

Gallery:

Google Earth image of Pool 8 area.
Yellow Bar Hassock marsh island, New York. Photo source: JoAnne Castagna, US Army Corps of Engineers.