Arriving in Venice years ago, Robert Benchley, the New York journalist and wit, is said to have sent a mock-panicked telegram to his editor: “Streets flooded. Please advise.” After the enormous storm last week, which genuinely panicked New York with its staggering and often fatal violence, residents here could certainly identify with the first line of Benchley's note. But what about the second? If, as climate experts say, sea levels in the region have not only gradually increased, but are also likely to get higher as time goes by, then the question is: What is the way forward? Does the city continue to build ever-sturdier and ever-higher sea walls? Or does it accept the uncomfortable idea that parts of New York will occasionally flood and that the smarter method is to make the local infrastructure more elastic and better able to recover? Gov. Andrew M. Cuomo on Wednesday gave a sea wall the nod. Because of the recent history of powerful storms hitting the area, he said, elected officials have a responsibility to consider new and innovative plans to prevent similar damage in the future. “Climate change is a reality,” Mr. Cuomo said. “Given the frequency of these extreme weather situations we have had, for us to sit here today and say this is once in a generation and it's not going to happen again, I think would be shortsighted.” But some experts in the field who have thought deeply about how to protect New York from huge storms like Hurricane Sandy — and especially from the coastal surges they produce — suggested that less intrusive forms of so-called soft infrastructure might prove more effective in sheltering the city than mammoth Venetian sea walls. Mayor Michael R. Bloomberg seemed to agree with them on Thursday when he said: “I don't think there's any practical way to build barriers in the oceans. Even if you spent a fortune, it's not clear to me that you would get much value for it.” According to the experts — architects, environmentalists and civil engineers — large-scale projects like underwater gates are expensive, cumbersome and difficult to build. More important, they say, such undertakings are binary projects that work just fine until the moment they do not. Whatever the way forward, Klaus H. Jacob, a Columbia University seismologist and an expert on urban environmental disasters, said the century-event of Hurricane Sandy could become, because of rising seas alone, an annual occurrence by 2100. “We know what we have to do,” said Dr. Jacob, who predicted last week's tragedy with eerily prescient detail in a 2011 report. “The question is when do we get beyond talking and get to action.” Among those actions already proposed are relatively minor alterations to the building code, to ban housing boilers and electrical systems in basements, and slightly more apocalyptic strategies, like one known as managed retreat, in which people would cede low-lying areas to the sea. While no one is calling for a mass and permanent exodus from the Rockaways, for instance, some experts, like Radley Horton, a climatologist at Columbia University, said that as parts of New York became more difficult — and costly — to protect, managed retreat needed at least to become “part of the public discussion.” Here, then, are three proposals — some traditional, some fantastic, but all at least theoretically workable — designed to reduce the effects of storms like Hurricane Sandy on three especially vulnerable New York neighborhoods: Lower Manhattan, the Red Hook and Gowanus sections of Brooklyn, and the northern shore of Staten Island. Lower Manhattan Marshy Edges, Absorptive Streets Picture a fringe of mossy wetlands strapped like a beard to Lower Manhattan's chin, and you are halfway toward imagining the plan to protect the financial district and its environs dreamed up by the architect Stephen Cassell and a team from his firm, Architecture Research Office, and a partner firm, dlandstudio. “Our goal was to design a more resilient city,” Mr. Cassell said. “We may not always be able to keep the water out, so we wanted to improve the edges and the streets of the city to deal with flooding in a more robust way.” Among the most disturbing images to emerge from the aftermath of the storm was that of a pile of cars floating upended in the waters of a parking lot near Wall Street. Lower Manhattan, where most of the borough's power failures occurred, is vulnerable to floods like this not just because it sits low in relation to the sea; it also juts out on heaps of artificial landfill, into the fickle waters of New York Harbor. It is probably not coincidental that the flooded areas of Manhattan, largely correspond to the island's prelandfill borders. To prevent incursions by water, Mr. Cassell and his planners imagined ringing Lower Manhattan with a grassy network of land-based parks accompanied by watery patches of wetlands and tidal salt marshes. At Battery Park, for instance, the marshes would weave through a series of breakwater islands made of geo-textile tubes and covered with marine plantings. On the Lower East Side of the island, Mr. Cassell and his team envisioned extending Manhattan by a block or two — with additional landfill — to create space for another new park and a salt marsh. Beyond serving as recreation areas, these engineered green spaces would sop up and reduce the force of incoming water. “When there's a storm surge, it creates an enormous amount of energy,” Mr. Cassell said. “Wetlands absorb that energy and protect the coastline.”
