NEW YORK -- Removable floodwalls would be erected in lower Manhattan, and levees, gates and other defenses would be built elsewhere around the city under a nearly $20 billion plan Mayor Michael Bloomberg proposed Tuesday to protect New York from storms and the effects of global warming.
The plan -- which would also include the building of marshes and the flood-proofing of homes and hospitals -- is one of the biggest, most sweeping projects ever proposed for defending a major U.S. city from the rising seas and severe weather that climate change is expected to bring.
It was outlined seven months after Superstorm Sandy drove home the danger by swamping lower Manhattan and smashing homes and businesses in other shoreline neighborhoods.
"This is urgent work, and it must begin now," Bloomberg said in a speech at the Brooklyn Navy Yard, acknowledging that much of the construction would extend beyond the end of his term this year.
"Piece by piece, over many years and even decades, we can build a city that's capable of preparing better, withstanding more and overcoming anything."
Environmentalists, real estate interests and local officials hailed the $19.5 billion proposal as far-reaching and comprehensive. It would dwarf the estimated $12 billion that the Army Corps of Engineers has spent so far to improve the New Orleans area's floodwalls, gates and levees since Hurricane Katrina in 2005.
"It's ambitious, but it's appropriately ambitious," said Judith Rodin, the president of the Rockefeller Foundation, who co-chaired a state storm protection study commission.
Still, it remains to be seen how the ideas will fare in a future mayoral administration and what kind of support -- financial and otherwise -- they might get from the federal government and other entities, not to mention from New Yorkers themselves.
Several mayoral candidates praised the mayor for thinking big, and Democrat Sal Albanese, Republican George McDonald and GOP front-runner Joe Lhota said they were inclined to pursue its major projects. Democratic front-runner Christine Quinn, who heads a City Council that is making its own proposals, called Bloomberg's report "a roadmap for future mayors."
But Republican John Catsimatidis, who has questioned whether the effects of climate change are overstated, asked whether the city was could spend far less and still get adequate protection.
"The $19.5 billion price tag is a huge amount of money," the billionaire candidate, whose businesses include oil, real estate and grocery stores, said in a statement.
Bloomberg said the city and federal money already allocated for Sandy relief would provide $10 billion for project, and the city believes it could get at least an additional $5 billion in federal money.
In a 400-page report on the plan, city officials said other options include a small surcharge on homeowners' insurance, around $1 a month for a homeowner who pays a $1,000 premium a year.
Bloomberg acknowledged that some of the ideas could block views of the water and otherwise prove controversial, but "if we're going to save lives and protect the lives of communities, we're going to have to live with some of the new realities."
After Sandy, at least some New Yorkers are ready for it, said James Molinaro, the borough president in hard-hit Staten Island, where the recommendations include a 15-to-20-foot levee to guard part of the island.
"The constituents that I talk to would take a 15-foot wall tomorrow," he said.
The plan doesn't call for moving people out of coastal communities. And it dismisses building major sea barriers with gates and levees, an idea some researchers and residents have promoted but Bloomberg has long called impractical.
That wasn't welcome news to Julie Menin, who chaired a lower Manhattan community board that called for a study of the idea in 2010. "It is something that we think needs to happen," she said Tuesday.
The mayor said smaller barrier systems should be built to help shield a creek in Brooklyn and possibly other waterways that can carry floodwaters inland.
The removable floodwalls along the waterfront in lower Manhattan would be a system of posts and slats that could be put up before a storm. Made of steel or some other impermeable material, they would be at ground level, perhaps combined with planters or an esplanade. The height would depend on the ground elevation and potential surge.
The approach is used along some Midwestern rivers and in the Netherlands, city officials said.
The recommendations also include building dunes in Staten Island and the Rockaways, bulkheads in various neighborhoods, and perhaps a levee and a sizeable new "Seaport City" development in lower Manhattan.
In addition, the mayor suggested giving $1.2 billion in grants to property owners to flood-proof their buildings and $50 million to nursing homes to improve theirs; making hospitals upgrade their pumps and electrical equipment to high flood-protection standards; and expanding beaches and marshes.
Bloomberg has long emphasized the threat climate change poses to the nation's biggest city, which has 520 miles of coastline. Tuesday's recommendations draw on updated predictions from a scientists' group convened by the city.
By the 2050s, 800,000 people could be living in a flood zone that would cover a quarter of the city's land, and there could be as many 90-degree days as is now normal for Birmingham, Ala., according to the panel.