Mayor Michael R. Bloomberg’s $20 billion program to armor New York City against climate change over the next decade includes extensive details, right down to the size of the concrete bulkheads proposed for the coast of Queens.
Yet even though the mayor is being praised for his foresight, the projects themselves face numerous obstacles before they can become a part of the city’s landscape and shoreline, officials and experts said on Wednesday.
They will have to pass through an array of government agencies, in City Hall, Albany and Washington. Zoning panels and community groups will weigh in. Billions of dollars in financing must be secured.
And of course Mr. Bloomberg, who announced the plan on Tuesday, is leaving office at the end of the year, and there is no guarantee that his successors will embrace all of the components.
In the months since the devastation of Hurricane Sandy, officials at all levels have endorsed proposals to protect the city from rising sea levels and major storms. And government has certainly carried out major infrastructure projects in the city in recent decades.
Still, Mr. Bloomberg himself can attest to the difficulties in obtaining approval for big plans. His proposal for a West Side stadium collapsed. One of his main environmental initiatives,congestion pricing, which would have charged drivers a fee to enter much of Manhattan, was rejected by Albany.
“Many of these solutions will require an unprecedented level of cooperation,” said Andy Darrell, New York regional director of the Environmental Defense Fund — not only between government agencies, but also the public and private sectors.
“We know how to do these things,” Mr. Darrell added. “What we have to do is clear a path.”
Others agreed that numerous challenges remained.
“A plan is a plan is a plan,” said Klaus H. Jacob, a geophysicist at Columbia University. “But there will be a hard reality of how to put this into action.”
“Many of the infrastructure systems that the city depends on are not under city control,” Mr. Jacob said.
The 438-page proposal released by Mr. Bloomberg on Tuesday has some 250 recommendations. They include the installation of levees, flood walls and bulkheads, as well as the creation of sand dunes and wetlands. The mayor would also like the city to renovate public housing, adjust flood insurance prices and establish an elevated neighborhood in Lower Manhattan called Seaport City.
Utility companies would upgrade their systems, and the city would develop a fuel supply system for use during severe weather disruptions. The sweeping plan includes provisions for coastal defenses, buildings, utilities, fuel and food supplies, health care, transportation and telecommunications.
Much of the $20 billion cost has already been covered by federal and city budget allocations, Mr. Bloomberg said. The city would have to raise an additional $5 billion. But some of the proposals are more speculative and would need billions of dollars more.
Several mayoral candidates said they supported Mr. Bloomberg’s intentions, while also pointing out problems with his plan.
In an interview, the City Council speaker, Christine C. Quinn, a Democrat, said she was “very confident” that the city would continue to allot the money needed to fulfill the $20 billion plan. “This is the biggest infrastructure project of our time, becoming climate-change-ready,” Ms. Quinn said.
But she added: “There isn’t one speech, one plan, or one piece of legislation that’s going to get it done. People are going to have to put egos aside, and jurisdictions aside.”
Another Democratic candidate, Public Advocate Bill de Blasio, said in a statement: “Many questions remain. As we review the plan, we must ensure that it truly serves the needs of low-income residents without a safety net, many of whom suffered the worst and longest-lasting impacts from Superstorm Sandy.”
While some credited the plan for being wide ranging, others expressed concern that it does not go far enough.
“I would have liked to hear something from the mayor that they were ready to invest in community-based organizations,” said Ron Shiffman, an urban planner and professor at Pratt Institute in Brooklyn.
“If you look at what happened on the Lower East Side, it was residents of public housing who became the focal point for a lot of the volunteerism that basically kept the community going for the first few weeks after the storm,” Mr. Shiffman said. “These were folks that were in many ways a set of first responders.”
Others pointed to the difficulties some residents and businesses still face in girding for the next big storm.
“Hurricane Sandy exposed and exacerbated deep inequities in our city based on income, race, housing and immigration status,” said Emmaia Gelman, a spokeswoman for Alliance for a Just Rebuilding, a coalition of unions and advocacy groups.