“Soft infrastructure” as storm surge defense alternatives
water or we give the shoreline a more irregular shape there will be more room to accommodate water.”
Among the techniques it proposed were restoring and enlarging wetlands, creating reefs and archipelagoes of artificial islands and seeding oyster beds. Spoils from harbor dredging and deepening, which is regularly performed by the U.S. Army Corps of Engineers, could be used for these beneficial purposes.
Reefs and wetlands would mitigate destruction by absorbing water and dissipating wave energy. Archipelagoes of small, artificial islands would weaken wave energy in the water column. Oysters and other mollusks would biologically filter and help cleanse the water in the bay.
Improved resiliency
“Through our research we found that improving water quality and wetlands ecology would improve the area’s resiliency to storm,” she notes. “If you can absorb water in wetland areas, it has a place to go. It can percolate into the earth instead of rebounding from a seawall or overtopping a wall. We can engineer solutions to absorb water and slow its velocity. There may still be flooding, but there will be less damage.”
Additionally, the report called for using — and extending — old abandoned piers and extracting slips into the city to allow water to enter flood zones in a more controlled way, thus minimizing damage. Calm water areas could be established behind piers, which would serve as storm surge buffers. Water would still enter some streets, but these could be engineered as bioswales, incorporating a simple gravity flow system that would enable the waters to be absorbed, and safely and readily recede.
Even if soft infrastructure strategies were implemented, some critical infrastructure would still need to be hardened, i.e. made waterproof, Seavitt notes. Specifically, she recommends protecting subway entrances and sidewalk grates to prevent flooding of the public transit system, relocating or hardening waterfront power plants and moving critical communications and power infrastructure out of the basements of commercial and residential buildings.
Soft infrastructure techniques can be applied, as well, to protect populated areas in the outlying coastal regions that suffered extensive storm damage such as Long Island, Staten Island, and the Jersey Shore. Offshore reefs and barrier islands could be created to protect shorelines and inhabited barrier islands. Many of these areas are shallower than the Upper Bay so it may be easier to work in them, she says.
One technology that could play a role in this process is a recent Dutch invention known as a sand motor, in which enormous quantities of sand are deposited offshore. Waves, currents and tides distribute it in a natural way, creating a protective barrier island.
Currently, Seavitt is working with Guy Nordenson & Associates and the Port Authority of New York and New Jersey on a pilot project to create an artificial island at the Gowanus Flats, a shallow section of Upper Bay off Brooklyn’s Sunset Harbor waterfront. She also notes that efforts are underway to create new oyster reefs around Governors Island as well as wetland restoration through the reuse of dredged sediment in Jamaica Bay.
