Storm Surge Defense Alternatives Needed To Protect Coastal New York
November 20, 2012

Storm Surge Barriers Needed To Protect Coastal New York

Lee Rannals for — Your Universe Online

New storm surge barriers are being proposed to help protect Lower Manhattan in New York City from storms such as those like the recent Superstorm Sandy.

Catherine Seavitt Nordenson, associate professor of landscape architecture in CCNY's Spitzer School of Architecture, is calling for the deployment of a storm surge strategy that combines elements of soft infrastructure with the hardening of existing infrastructure like the subway system, highways and power plants.

Governor Andrew Cuomo and other officials had initially proposed building storm surge barriers to help protect from future catastrophes, but Nordenson argues her strategy would be better.

“If you mitigate to protect Lower Manhattan, you increase the impact in other areas,” Nordenson said in a statement. “Everyone outside of the surge protection zone would be in jeopardy because the water doesn´t get reduced, it just goes somewhere else. It´s an environmental justice issue. You can´t just save Wall Street.”

She said that the idea of soft infrastructure is to use techniques from nature and ecology to improve resiliency from these storms.

“Environments that are more resilient bounce back faster after storms, and greater resiliency reduces the velocity of and damage caused by the water´s surge," Nordenson added.

She points out that it would be much less expensive than building storm surge barriers, with costs running up in the hundreds of millions rather than the billions.

Nordenson presented a paper published in 2010 in collaboration with structural engineer Guy Nordenson and architect Adam Yarinsky. During this paper, the team focused on New York's Upper Bay, including Manhattan, Brooklyn, Staten Island and New Jersey.

The paper's proposal consisted of strategies for adapting to and mitigating the effects of rising sea levels caused by climate change, including increased potential storm surges from hurricanes.

“We wanted to show how soft infrastructure could be used to transform the coastal edge in order to create a healthier ecology and reduce the extent of storm damage,” she said. “There are things we can do besides building higher and higher seawalls everywhere. For example, if we replace a wall with a gradient edge that slopes into the water or we give the shoreline a more irregular shape there will be more room to accommodate water.”

The original paper proposed restoring and enlarging wetlands, creating reefs and archipelagos of artificial islands and seeding oyster beds.

Reefs and wetlands under this scenario would mitigate destruction by absorbing water and dissipating wave energy, while the artificial islands would weaken wave energy in the water column. The oysters and other mollusks would biologically filter and help cleanse the water in the bay.

“Through our research we found that improving water quality and wetlands ecology would improve the area´s resiliency to storm,” Nordenson explained. “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.”

The report called for using abandoned piers and extracting slips into the city to allow water to enter flood zones in a more controlled way.

Engineers could establish calm water areas behind piers, which would be able to help serve as storm surge buffer. Water may still enter the streets, but these could be engineered as bioswales, enabling the waters to be absorbed.

Nordenson says that even if soft infrastructure strategies were implemented, some critical infrastructure would still need to be hardened, making them waterproof.

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.

Professor Seavitt is working with Guy Nordenson & Associates and the Port Authority of New York and New Jersey on a project to help create an artificial island at the Gowanus Flats. She also said efforts are currently underway to create new oyster reefs around Governors Island as well as wetland restoration through the reuse of dredged sediment in Jamaica Bay.