Living breakwaters will increase coastal resilience

As the frequency of extreme weather events is increasing, and the sea levels are continuing to rise, New York City has amped up efforts to hinder the potential damage that follows. Staten Island is especially at high risk of experiencing severe losses and damages during flooding. Big parts of the shoreline have been experiencing erosion for the past 35 years, increasing the vulnerability of the area. In 2012, the waves caused by Hurricane Sandy damaged the Staten Island shoreline to such an extent that businesses and homes were damaged, lives were lost, and the local economy was harmed significantly. To increase resilience, the New York State Governor’s Office of Storm Recovery (GOSR) has initiated a project called “Living Breakwaters”. Ramboll is leading the construction management team and acting on behalf of GOSR. Ramboll’s responsibilities include supervising and overseeing the planning, coordination, and implementation of the project; ensuring construction work complies with the project’s design and schedule; and ensuring that safety and quality standards are met. Ramboll is collaborating with our subcontractors Baird Associates, Entech Engineering, KS Engineers, Trophy Point, Mavec Advisers, Almas Construction, and Certified Site Safety. The design team consists of SCAPE and COWI, and the contractor is Weeks Marine. SCAPE became the design engineer by submitting a winning proposal for the Rebuild by Design competition funded by the US Department of Housing and Urban Development (HUD).

The Living Breakwaters project is carried out in Tottenville, the southernmost point of Staten Island. Losing more than 90 centimetres (3 feet) of shoreline per year in some areas, the town holds the record for highest average erosion rate on Staten Island. It was once known as The Town the Oyster Built due to the many oysters along the shoreline. However, the shoreline now lies unprotected and exposed to wave action due to overharvesting, channel dredging and pollution that has led the natural habitat of oysters and other marine life to vanish. Breakwaters are large structures of rocks fitted into marine mattresses and submerged into the water with an outer layer of armour stones and ecologically enhanced concrete armour units. “Ecologically enhanced” refers to their special design, which is also what makes these breakwaters “living”. The armour units on the outer layer are designed with a concrete mixture and surface that will enhance biological activity and help bring back local marine species. A big part of the design solution includes rebuilding the natural habitat of oysters by installing oyster reefs on the breakwaters alongside a floating oyster nursery. The oysters serve as a water filter and increase water quality, while also helping to hold the breakwaters themselves in place. The breakwaters have features similar to a natural reef – ridges, narrow spaces, protruding rocks – that will help control wave action and help to re-establish the natural environment that once was. Once finished, there will be approximately 700 metres (2,400 feet) of living breakwaters located between 250-500 metres (790-1,800 feet) from shore.

Rebuilding the oyster habitat by adding oysters to the breakwaters does not only decrease the risk of flooding. The water-purifying quality of oysters is a big benefit for the local community and will also help revive the natural habitat and bring back local species. To ensure that the revived habitats are well taken care of, the project also includes an educational programme in the local schools and engagement through the Citizens’ Advisory Committee (CAC). In addition to the installation of breakwaters, the project includes shoreline restoration from Manhattan Street to Loretto Street, an area especially prone to erosion and where public and private assets are vulnerable. The breakwater system is also designed to capture sediments along the shoreline, contributing to reverse erosion and protecting the newly replenished shoreline. With this design, the project will not only increase the physical resilience of the area, but also the social and environmental sustainability.