Mayor Michael R. Bloomberg outlined a far-reaching plan on Tuesday to protect New York City from the threat of rising sea levels and powerful storm surges by building an extensive network of flood walls, levees and bulkheads along its 520 miles of coast.
The mayor said the plan would initially cost about $20 billion, and eventually far more. The city would spend the money on fortifying infrastructure like the power grid, renovating buildings to withstand hurricanes and defending the shore, according to a 438-page report on the proposals.
The proposals, in all, would change the look and fabric of the city, though not until well after the mayor leaves office at the end of the year.
Still, he emphasized that Hurricane Sandy was such a devastating event that the city had to move immediately.
This plan is incredibly ambitious and much of the work will extend far beyond the next 203 days but we refused to pass the responsibility for creating a plan onto the next administration, he said in a speech at the Brooklyn Navy Yard. This is urgent work, and it must begin now.
The report details 250 recommendations, including the installation of flood walls and other measures to protect some of the areas that were hit worst by the hurricane in October.
The plan covers so many parts of the city and proposes such an array of projects that the cost could change and given the history of such large projects, it is likely to grow substantially.
Not included in the estimate are some of the more ambitious projects envisioned in the report that require further study, like the construction of a so-called Seaport City, just south of the Brooklyn Bridge in Manhattan, modeled after Battery Park City, which would protect Lower Manhattan but cost billions more.
The administration said that roughly half of the currently estimated $20 billion cost over the next decade would come from federal and city money that has already been allocated. An additional $5 billion would be covered by aid that Congress has already approved. Most of that money was allotted, through a variety of programs, in the aftermath of Hurricane Sandy, according to the report.
The city would have to raise an additional $5 billion.
Mr. Bloomberg said that the price tag was high, but that the cost of not taking action would be higher. Hurricane Sandy caused $19 billion in damage and loss of economic activity for the city, he said, and if a similar storm were to strike three decades from now, the cost could be $90 billion.
This is a defining challenge of our future, he said.
Mr. Bloomberg delivered the recommendations in an elaborate presentation, including a documentary-style video and a glossy report, that underscored how he is making climate change a signature issue toward the end of his tenure. In recent months, he has sought to contrast his activist stance on climate change with what he has said is the unwillingness of Washington to tackle these issues.
He chose to speak not at City Hall, but at the Brooklyn Navy Yard, which was damaged by four and a half feet of floodwater during the hurricane.
Mr. Bloombergs speech came a day after his aides released information on what they predicted would be the effect of climate change on the city.
Officials estimated that more than 800,000 city residents would live in the 100-year flood plain by the 2050s more than double the 398,000 currently at risk, based on new maps released by the Federal Emergency Management Agency. The number of days with temperatures above 90 degrees is expected to jump sharply.
Environmental and business groups largely praised Mr. Bloombergs initiative, though some experts questioned whether the city needed to consider evacuating some areas.
I think that the mayors plan is great, said Robert S. Young, director of the Program for the Study of Developed Shorelines at Western Carolina University. I really appreciate the fact that he acknowledges the problem and understands climate change and the fact that we need to prepare for it. But everyone needs to understand that you cant guarantee protection for infrastructure that is in vulnerable locations, no matter how much money you throw at the problem.
In the first phase of building defenses, the report released on Tuesday calls for erecting barriers at Hunts Point in the Bronx to protect the food distribution center, on the East Harlem waterfront along Franklin D. Roosevelt Drive, on the East Side where several of the citys hospitals are, on the Lower East Side, in Chinatown, in the financial district and in Red Hook, Brooklyn.
On Staten Island, the plan calls for a system of permanent levees.
Along some parts of the coast, stone or concrete bulkheads would be installed, while in other places, dune systems would be built.
The citys power infrastructure also should be better protected, the report said. Currently, 53 percent of power plants are in threatened neighborhoods. By the 2050s, according to the report, 97 percent will be.
Much of the worst damage during Hurricane Sandy occurred in buildings erected before 1961, according to the report. The plan calls for $1.2 billion to be made available to property owners for renovations, like raising critical equipment, upgrading foundations and reinforcing exterior walls.
The plan calls for the citys hospitals to protect electrical equipment, emergency power systems and water pumps better by 2030.
Even before the hurricane, the mayor had commissioned a panel to study the changing climate, rising oceans and more powerful storms, and to propose plans to address the risks.
The panel is part of the citys broader, so-called sustainability campaign, known as PlaNYC. Much of what is called for in that plan is meant to have an impact over the course of many years. For instance, one of its key goals is to reduce carbon emissions 30 percent by 2030. The city is halfway there, with emissions cut 16 percent, city officials said.
After Tropical Storm Irene forced the evacuation of hundreds of thousands of residents along the citys coast in 2011, there were renewed questions about whether long-term goals were enough or whether more urgent action was needed especially as more people were settling along the citys shoreline.
During the Bloomberg administration, much of the waterfront has been revitalized, with the city spending hundreds of millions of dollars to improve parks, build esplanades and create the infrastructure necessary for residential development.
Developers have rushed to put up expensive rental and condominium towers from Battery Park City to Long Island City, transforming warehouse and wharf districts.
But as the administrations own waterfront plan, Vision 2020, warned in 2011, the development came with risks.
By 2050, sea levels could be 12 to 29 inches higher, according to the plan. By 2080, they could be about 55 inches higher. Those estimates have been revised upward recently.
While the city was spared a direct hit by Tropical Storm Irene, experts knew how close the storm had come to doing terrible damage. If the storm surge been 12 inches higher, city subways and thousands of homes would have been flooded.
One year later, Hurricane Sandy fulfilled even the most dire predictions.
No matter how far weve come, Mr. Bloomberg said on Tuesday, we face real, immediate threats.