How Cities Plan to Keep the Sea at Bay in an Age of Climate Change Hurricane Sandy was bad. Now imagine a near-future that is markedly worst, where storms are not only more vicious and more frequent, but ocean levels are higher too. According to a team of experts in New York, coastal waters there are expected to rise some six inches per decade, rising at least two feet by the middle of the century, according to a report by my colleagues David W. Chen and Mireya Navarro. Andrew C. Revkin extensively discusses on his Dot Earth blog how climate change affects heavy storm systems. He suggests that not only gradually and permanently rising seas are in our future, but more flooding caused by violent storms like Sandy. On Tuesday, after New York City felt the full brunt of superstorm Sandy, Gov. Andrew M. Cuomo announced that the state was considering a system of surge barriers and levee systems, David and Mireya report. "We are only a few feet above sea level," said Mr. Cuomo, pointing out that once water breaches the city's defenses, subway tunnels, building foundations and underground infrastructure like parking garages are immediately faced with flooding - as thousands of New Yorkers who lost power, public transportation, basements and their cars experienced just the last week. With the immediacy of a systemic, long-term threat far more apparent in the wake of the so-called Frankenstorm, New York officials - who had already discussed the threat posed by rising sea levels before Sandy - are joining a long list of experts and administrators who are seeking to protect their cities from the high waters associated with climate change. This weekend, my colleague Alan Feuer reported on several flood-control plans for various parts of New York. The physical barriers to the sea are estimated to cost around $10 billion. If the city builds them, New York (once known as New Amsterdam) would be following in the footsteps of old Amsterdam, where parts of the city are up to 6.5 meters (21 feet) lower than the North Sea, thanks to an intricate and very expensive system of levees, polders and dams. Taking the model of physical flood protection one step further, Venice, which for centuries has suffered the effects of Acqua Alta (high water), will inaugurate the Mose system in 2015. Named after the prophet Moses (Mose in Italian) who parted the seas, the €5.5-billion movable floodgate rises from the ocean floor with the help of compressed air when storm waters threaten the city. This video explains the project: Watch on Youtube. In his excellent article, Alan also cites a project for Lower Manhattan by Stephen Cassell and his firm, Architecture Research Office, that would not rely on physical barriers but would flood-proof the area, so that high water would do less damage. Such a model is currently under discussion in Durban, South Africa, where the money to build expensive infrastructure to keep the sea at bay is much harder to come by than in comparatively wealthy New York. As part of its plan for protection against increasing flooding, Durban is redrawing city districts and keeping city infrastructure away from areas that are at risk of flooding. Mr. Cassell and Kate Orff, a landscape designer who has proposed a plan to protect the low-lying Red Hook and Gowanus neighborhoods in Brooklyn, also advocate natural biomass in the fight against rising seas. From marches and artificial islands to oysters, natural and active biomass has great potential to mitigate floods. Both New Orleans and Durban (among many other cities) are betting on nature to act as a natural sponge. And while global models will be more attentively studied after last week's disaster, some more ready solutions have been proposed. Home Land Security has developed, in conjunction with West Virginia University, ILC Dover and Pacific Northwest National Laboratory, gigantic plugs that can, when filled with 35,000 gallons of water, plug subway tunnels to prevent flooding of the system.