After the flooding caused by Superstorm Sandy in 2012, a proposal was developed to build storm surge barriers to protect New York City and nearby municipalities. Given the rising sea levels and increasingly violent storms associated with climate change, many argue that this storm barriers are an absolute necessity to prevent more devastating flooding in the immediate future.

The U.S. Army Corps of Engineers is now considering six different plans involving massive in-water barriers and/or land-based floodwalls, dunes and levees intended to “manage the risk of coastal storm damage” to New York Harbor and the Hudson Valley.

On the other hand, a number of environmentalists argue that the storm surge barriers as designed would effectively threaten the very existence of the Hudson as a living river.

Storm surge is scary as hell. I vividly remember the evening of October 29th, 2012 when Superstorm Sandy hit New York harbor. At our home in downtown Jersey City, we had water coming towards us from three directions. Suddenly about 9PM, just before the power went out, the surge rolled up our block, stopping a couple hundred feet from our house. We were among the lucky one that night.

Across the river in New York City, parts of the subway system were flooding. All road tunnels into Manhattan, except the Lincoln Tunnel, were flooded and closed, as were subway tunnels under the East River and the PATH subway system. Blocks of downtown Manhattan went under water, as did neighborhoods in Brooklyn and Staten Island. Thousands of homes and an estimated 250,000 vehicles were destroyed during the storm. The economic losses in New York City alone were estimated to be roughly $19 billion with an estimated $32.8 billion required for restoration across the state.

There are relatively small storm surge gates in the United States in Stamford, CT; in Providence, RI; and in New Bedford, MA. Internationally, larger barrier systems protect more than a dozen major cities, including the Thames Barrier protecting London; the Delta Works protecting the south of the Netherlands; the MOSE Project protecting Venice; and the Saint Petersburg Dam protecting St. Petersburg, Russia.

So what are the objections to storm surges barriers to protect New York harbor?

The problem is that building the barriers to protect the city just might destroy the Hudson River. The largest barrier would be at the mouth of the harbor between Staten Island and Brooklyn. While there would be a gate to allow marine traffic, the barriers would drastically restrict tidal flows.

As noted by the Riverkeeper: From Day One, these offshore barriers would start to restrict the tidal flow, contaminant and sediment transport, and migration of fish. They would impede the tidal “respiration” of the river. We fear that a slow death would be inflicted on the river, and that in time, the barriers would slowly, but surely, strangle the life out of the river as we know it.

They would significantly restrict migrations of striped bass, Atlantic sturgeon, herring, shad, eel and other species essential to the Hudson estuary. They would prevent the ocean tide from flushing New York Harbor, causing contamination to be more concentrated there. And they could restrict rainstorm flood waters, like those we experienced during the massive rainfall of Irene and Lee in 2011, from leaving the Hudson.

Unrestricted tidal exchange is essential to move sediment and flush contaminants. If tidal exchange is restricted, the harbor would require much more dredging to maintain shipping channels. Sewage and other contaminants would flush to the ocean more slowly, resulting in more pollution for our already contaminated harbor and river. Higher nutrient levels would lead to more frequent algae blooms and lower dissolved oxygen essential for aquatic life.

New York City listed its own reservations in the New York City Economic Development Corporation (NYCEDC) 2013 report “A Stronger, More Resilient New York,” and noted that environmental impacts like fish migration would require extensive study.

“In theory, one way to achieve the City’s goals for its coastline may be the construction of massive protective infrastructure, such as harborwide storm surge barriers at the entrances to New York Harbor,” the report said. “As attractive as the concept of a single “silver bullet” solution may be, though, a closer examination of this strategy strongly suggests that relying on such a solution would pose significant risks to the city that far outweigh its theoretical benefits.”