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Great Kills Harbor Breakwater Study

The DEC Hudson River Estuary Program and the New York City Mayor's Office of Recovery and Resiliency and Department of City Planning have released a study evaluating the use of offshore breakwaters to mitigate wave action and erosion at Great Kills Harbor, on the eastern shore of Staten Island. The study was funded through a partnership with the New England Interstate Water Pollution Control Commission.

Image of marina in Great Kills Harbor
Marina in Great Kills Harbor-Photo credit: Biohabitats

Staten Island is highly exposed to the Atlantic Ocean and was significantly damaged by Hurricane Sandy. The study models and analyzes the economic, ecological, and hazard mitigation reduction potential of two design options for offshore breakwaters near the mouth of Great Kills Harbor. The study was based on initiative # 13 of the New York City report: A Stronger, More Resilient New York (SIRR) which specifically calls for the study of an offshore breakwater system in this location. The study was jointly conducted by Ocean and Coastal Consultants/COWI, SCAPE/Landscape Architecture, Parsons Brinkerhoff, ARCADIS, and Biohabitats. To read the Great Kills Harbor Breakwater Study, please visit the New York State Water Resources Institute website (leaves DEC website).

What are offshore breakwaters?

Offshore breakwaters are rocky structures in the water column that help to reduce wave height and energy, resulting in less damage and erosion on land. Breakwaters can serve as an example of ecologically-enhanced shoreline protection because they can provide additional aquatic habitat benefits. The height, layout, and extent of offshore breakwaters determine their ability to provide protection. Offshore breakwaters are best used in a multilayer resilience strategy and not as a singular solution for risk reduction.

What does the study examine?

image showing design option one
Design Option One: Breakwaters at mouth
of Great Kills Harbor and off Crooke's Point.

The study examines the technical feasibility and marine habitat benefits and consequences of an offshore breakwater-system outside of Great Kills Harbor by examining two design options, developed with stakeholder input, under four storm and sea-level rise scenarios. Modeling results were analyzed for economic, ecological, social, implementation, and adaptation/maintenance considerations.

What is in the final report?

The final report details the evaluation of the two offshore breakwater-system design options. It includes the results of the hydrodynamic modeling, the ecological survey and assessment, and an analysis of the potential damage-reduction benefits and regulatory considerations. The report also covers lessons learned from the project, further research and modeling needs, and applicability of the results beyond Staten Island.

Design Alternatives

image showing design option two
Design Option Two: Segmented near-shore breakwater
and dune enhancement on Crooke's Point.

The graphics at right depict the two design alternatives modeled in the study. The brown lines in the water represent breakwaters. The brown lines on land represent dune enhancements. The blue solid and hashed line represents the current USACE navigation channel. Graphics: Scape Landscape Architecture

What are the key findings?

The study found that off-shore breakwaters can be effective in reducing wave action and erosion along high-energy shoreline areas outside the mouth of Great Kills Harbor. However, additional modeling would be needed to optimize the height, spacing, and length of the breakwaters if they were selected as part of a larger strategy for risk-reduction at this site. The study also found that in-water structures may not be cost-effective solutions for reducing coastal hazards within the Harbor itself, due to the natural protection already provided by a nearby peninsula, Crooke's Point.
The evaluation also suggests that offshore breakwaters can provide ecological benefits by lowering wave energy on the lee side of breakwaters and providing in-water structural diversity. However, more modeling is necessary to determine potential effects of breakwaters on water-quality and sediment movement.

How will the plan be used?

This study clarified modeling and research needs that are critical to improving our understanding of how to:
1) optimize the use of breakwater systems in high-energy environments
2) reduce vulnerability to coastal hazards in and around Great Kills Harbor.
The project results are also informing the design and evaluation of the Governor's Office of Storm Recovery's Living Breakwaters project near Tottenville, Staten Island, funded by the federal Department of Housing and Urban Development. Moving forward, the Hudson River Estuary Program, New York City Department of City Planning, and the New York-New Jersey Harbor & Estuary Program are jointly organizing efforts to collaborate with stakeholders on priority research topics related to coastal green infrastructure in the New York-New Jersey Harbor Estuary.